text:
|Publication number
|Publication type
|Application number
|Publication date
|May 30, 2000
|Filing date
|Oct 7, 1997
|Priority date
|Aug 26, 1997
|Fee status
|Publication number
|Chris D. Alber, Randolph H. Ware, Christian Rocken, Fredrick S. Solheim
|Original Assignee
|University Corporation For Atmospheric Research
|Export Citation
|BiBTeX, EndNote, RefMan
|Patent Citations (8), Referenced by (42), Classifications (6), Legal Events (4)
|External Links: USPTO, USPTO Assignment, Espacenet
This invention was made with Government support under Agreement No. ATM-9209181 awarded by the National Science Foundation. The Government has certain rights in this invention.
This application is a regular utility application and a continuing application following provisional application 60/056,999 filed Aug. 26, 1997.
This invention relates to high resolution surveying systems and, in particular, to a system using satellite transmissions, such as those that may be obtained from global positioning satellites ("GPS"), for remote sensing of slant-path water delay, which is used to correct GPS survey errors that arise from variations in atmospheric water content.
GPS systems are now in use throughout the world. The GPS industry grosses more than a billion dollars each year in sales and service by providing reliable, quick, and accurate position measurements. Even so, there are practical limits to the precision of measurement that is obtainable from GPS systems. Traditional GPS surveys can obtain -2 to 5 mm horizontal and -4 to 10 mm vertical precision over 1000 km baselines.
The GPS system was developed for navigation and time transfer, and was later demonstrated as a tool for highly accurate surveying. The GPS satellite network includes a constellation of twenty-one active satellites and three spares in six precise orbital planes over the Earth at high altitudes of about 20,000 km where the satellites broadcast 1.2 and 1.6 GHz carrier signals. These satellites contain atomic clocks that permit signal transmission at precise times. Most ground-based dedicated GPS receivers include a data almanac containing satellite positions by times.
The satellite typically orbit the Earth twice a day. Satellite monitoring stations on each orbit monitor ephemeris errors in a satellite's altitude, position, and speed. These errors are due to gravitational pulls from the moon and sun, as well as the pressure of solar radiation impinging upon the satellite. The ephemeris error corrections are uploaded to the respective satellites, which are programmed to broadcast corrections to their own position-indicating signals.
The GPS network also contains an array of hundreds of Earth-based GPS receivers deployed world wide. Each GPS satellite transmits two radio signals at different frequencies to provide the precise time and satellite position. A GPS receiver receives signals from at least three GPS transmitters to determine its precise location on the Earth using a triangulation method. A fourth satellite signal is conventionally used to correct for variations in the timing of signal transmissions with respect to other satellites.
GPS computers calculate position using conventional techniques to determine distance as a function of the velocity of light and time. The calculation of distance as a function of the velocity of light and time is complicated because the speed of light varies depending upon the content of the ionosphere and the atmosphere. The ionosphere includes a blanket of electrically charged particles at an altitude of about 80 to 120 miles above the Earth. These charged particles cause variations in the velocity of light passing through the ionosphere. GPS satellites broadcast signals of different frequencies to permit calculations that eliminate ionospheric errors. Earth-based GPS receivers of better quality process these dual signals to eliminate ionospheric errors. Atmospheric errors due to refractivity are more difficult to correct, and the variable portion in the refractivity of minor atmospheric components, such as water vapor, are traditionally ignored.
Commercially available software packages are capable of performing GPS position calculations, and these programs are accompanied by extensive documentation of the exact calculations and corresponding algorithms. One example of this type of well documented software is the Bernese software, which is described in Beutler et al, "GPS Software Version 4.0," Univ. Berne, (September, 1996). Other sources of GPS information are available, such as the International GPS Service precise orbits described in Neilan, "The Evolution of the IGS Global Network, Current Status and Future Prospects," International GPS Service for Geodynamics, 1994 Annual Report, JPL Pub. 95-18, 25-34 (1995).
There is a need for GPS surveying systems having better precision of measurement than can be obtained from existing systems. Highly accurate location measurements are needed to monitor the Earth's crustal deformation. Many cities are at risk of impending geologic catastrophes, such as earthquakes and volcanos. This risk is particularly acute in cities that are located in geologically active areas, such as ocean-continent subduction zones or rift zones. Scientists also need to monitor crustal deformation in areas that are not at substantial, risk, and it is difficult to justify the expense of building comprehensive fixed monitoring facilities in areas where risk is not severe. Present GPS systems lack the precision that is desirable for effective monitoring of the earth's crustal deformation.
Tsuji et al., "Tremors! Monitoring Crustal Deformation in Japan" GPS World pp. 18-29 (April 1996) describes how Japan's Geographic Survey Institute has monitored Japan's crustal deformation for about one-hundred years. In 1882, Japan's Geographic Survey Institute began the construction of a triangulation network using theolodytes constructed of stone monuments weighing sixty kilograms and wooden observation towers ranging from ten to fifteen meters in height. The old triangulation system became operational in 1911, and changed to a laser range finding system in 1970. The laser range finding system had a 1.5 cm error in ten km, which is referred to in the art as a 1.5 ppm accuracy. The laser range finding system has now been replaced by a system providing GPS surveys from a plurality of fixed towers. The Tsuji et al article states that present GPS surveys can produce relative accuracies of ten parts per billion, i.e., about ten mm across ten km. This level of accuracy is mandatory for crustal deformation studies.
The state of the art now is that atmospheric water content provides the principal uncorrected source of error in high resolution GPS surveys. Three atmospheric constituents are based on water in its various forms including liquid (water), solid (ice) and gas (vapor). Although at any one time approximately 99% of the Earth's water is in liquid and solid form, water vapor is an important and highly variable atmospheric constituent that acts over a wide range of temporal and spatial scales. The combined effects of rain, snow, and ice particles are typically twenty times less than the effect of atmospheric water vapor on GPS position determinations.
Many factors including pressure, temperature, and proximity to a water source can determine the quantity of water vapor in the atmosphere. For example, atmospheric water vapor content ranges from at or near 0% to about 4% by volume depending on the temperature and availability of liquid water. Water vapor content is also highest in moist and/or low pressure regions, and it is lowest in arid and/or high pressure regions. Further, only a certain maximum volume of water vapor is possible per volume of air depending on the temperature. As the air warms and/or pressure decreases, the maximum possible water vapor content increases. Alternatively, as the air cools and/or the pressure increases, the water vapor content decreases. Once the maximum water vapor content or saturation threshold is reached for any given temperature, the excess water vapor is released as condensation and/or precipitation in the form of rain or ice.
There is a need for using the GPS system to measure atmospheric water vapor in correcting for the effects of water vapor refractivity that induce errors in GPS position calculations. Existing methods for detecting and quantifying water vapor are undesirable because they can only be implemented on a local scale over land thereby leaving vast gaps in global meteorological continuity. The largest gaps occur over oceans where most atmospheric conditions originate. Although the existing atmospheric sensing systems listed below exhibit high resolution capabilities on a local scale, it is not practical to deploy such systems on a global scale because they are expensive to implement or maintain on a global scale and they lack adequate temporal and/or spatial resolution for realistic use on a global scale.
The radiosonde, an expendable balloon-borne instrument package that relays temperature, humidity, and pressure data to a ground receiver by radio signals, is the traditional cornerstone of the worldwide operational weather analysis and prediction system through deployments twice daily at several hundred sites around the world. However, the twice daily radiosonde deployments are primarily over land and are sparsely distributed due to cost considerations. For these reasons, radiosonde data is too costly and localized to support high resolution global meteorology.
Commercials air carriers presently provide real-time wind, pressure, temperature, and humidity readings around the world as part of a system called Aeronautical Communications Addressing and Reporting System (ACARS). Although the ACARS system provides about 10,000 readings per day world wide at a cost about 100 times less than the recurring cost of radiosondes, the vast majority of ACARS readings are taken around airports and along common flight paths at established cruise flight levels which limits the spatial scope of this otherwise valuable data.
Earth-based Differential Absorption Lidar (DIAL) and Raman Lidar systems are used to provide wind and water vapor profiles in remote areas. However, such systems are not economic to install and maintain, they do not penetrate cloud cover, and the lasers used are highly energized and are therefore not eye-safe.
Water vapor radiometers are instruments that measure microwave energy emitted by the atmosphere to estimate integrated water vapor. Integrated water vapor ("IWV") is a measure of the depth of liquid water that would result if a column of water vapor were condensed into liquid water. Earth-based upward-looking water vapor radiometers estimate IWV by measuring radiative brightness temperatures against the cold background of space. However, upward-looking water vapor radiometers must be "tuned" to local conditions using independently obtained atmospheric profile, and although they generally exhibit good temporal resolution in relatively clear atmospheric conditions, they provide only localized IWV data. Further, unless properly equipped upward-looking radiometers are virtually useless in rain. Alternatively, satellite-based downward-looking radiometers perform well over water and consistent temperature land masses by viewing microwave emissions from the atmosphere and the underlying Earth's surface. However, although downward-looking radiometers generally exhibit good spatial resolution they exhibit poor temporal resolution and perform poorly over most land masses. In either case, water vapor radiometers as a whole are not practical for global scale meteorology due to their cost, limited view, and performance characteristics.
Fourier Transform Infrared Radiometer (FTIR) systems can provide high resolution satellite-based and Earth-based temperature and water vapor profiles by using a recursive solution of the radiative transfer equation to provide a vertical profile from the ground up. Although this method can provide vertical resolution of several hundred meters to a kilometer in the lower troposphere, the system exhibits poor performance in the presence of cloud cover and infrared active gases such as tropospheric ozone.
Unmanned Air Vehicles (UAV's) provide high resolution data in regions inaccessible to other systems discussed above. However, unmanned aircraft are too costly for continuous global sensing, they lack adequate spatial and temporal resolution and are typically only justified in specialized research applications.
The GPS system can also be used to produce high resolution atmospheric tomography by integrating the IWV measurements from Earth-based GPS receivers with radio occultation measurements from at least one Low Earth Orbiting (LEO) satellite. As used herein, the phrase "atmospheric tomography" refers to a profile of structure in the atmosphere constructed from water vapor measurements gathered at points within the atmosphere where a zenithal GPS signal received by an Earth-based GPS receiver intersect with a horizontal GPS signal received by a LEO. A LEO satellite orbits the Earth faster than the higher orbit GPS satellites so that a GPS signal received by a LEO satellite transects the Earth's atmosphere in the moments prior to the GPS signal being eclipsed by the Earth. The transecting GPS signal slices the atmosphere along a long horizontal limb path, thereby revealing important structural information because the signal is subject to a time series of Doppler shifts due to the refractive index of the atmosphere. However, one disadvantage with the radio occultation technique is that it produces only periodic soundings that occur at different points around the Earth due to the difference in LEO and GPS satellite orbital periods. Another disadvantage is that soundings using the radio occultation technique are limited in spatial usefulness because the long horizontal limb path measurements are smeared along at least a 200 km horizontal section of the atmosphere with relatively few intersecting zenithal PWV soundings therebetween for reference points.
The GPS geodetic method described by Dixon in "An Introduction to the Global Positioning System and Some Geological Applications", Rev. Geophys., 29, 249-276, (1991), provides a method for using the GPS system to estimate atmospheric zenith path delay. The existing technique for atmospheric sensing of water vapor using the GPS system is limited primarily due to the assumption of atmospheric symmetry, minimal error compensation, and zenith-only path delay estimations over land masses. The GPS system uses all incoming GPS signals at once and the assumption of atmospheric symmetry induces corresponding errors.
Zenith path corrections according to the Dixon article are inadequate because the assumption of uniform atmospheric symmetry is invalid. Rocken et al, "The Measurement of Atmospheric Water Vapor: Radiometer Comparison and Spatial Variations, IEEE Trans. Geosci. & Remote Sensing, 29, 3-8, (1991) reports a twenty percent azimuthal variation in radiometer measurements of integrated water vapor at 30� elevation. These variations are significant to GPS position calculations.
In the past, crude attempts have been made to remove errors due to slant water path delay from GPS position calculations, however, expensive and bulky equipment is required and the precision of measurement could still improve. Rocken et al., "Sensing Atmospheric Water Vapor with the Global Positioning System," Geophys. Res. Lett., 20, 2631-2634, (1993), reports one such attempt which used pointed radiometers to track GPS satellites for the estimation of slant path water vapor. The vapor estimate was converted into an estimate of slant path wet delay. These types of experiments result in root mean square precision estimates ranging from 2.6 to 12 mm.
For the reasons stated above, there exists a need for a simplified GPS survey system that corrects for GPS survey errors that derive from water vapor content. This need has heretofore not been satisfied.
The problems described above are solved and a technical advance is achieved in the field by correcting for GPS survey errors that derive from azimuthal variations in the refractivity of atmospheric water vapor. No other apparatus is required for implementing these corrections other than the GPS receiver and computer. Slight modifications to the conventional GPS position calculations are made to implement these corrections, as described below. Thus, the GPS position calculation method facilitates a significant improvement in the precision of measurement, which may be advantageously accomplished through use of equipment that is not so expensive and bulky as the prior slant water path delay correction techniques which made use of radiometers. The methodology of the present invention lends itself equally well to a variety of satellite positioning systems and related equipment including the Japanese GPS augmentation system (see, e.g., Divis, Getting a Fix on Japan's Nav Plans, GPS World pp. 14-20 (July 1997) and the Russian GLONASS system (see, e.g., Langley, GLONASS: Review and Update, GPS World pp. 46-51 (July 1997).
It has been discovered that GPS position calculations using independent estimates of atmospheric water vapor permits precision of measurement to a root mean square vertical precision of 1.2 mm and sub-millimeter precision on the horizontal scale. Modified radiometers were used as the independent source of measurement to obtain this extremely high survey precision. In addition, GPS antennae were fitted with choke collars 25 cm in width to eliminate ground-reflected multipath for this purpose. This level of precision significantly enhances the ability of scientists to monitor the Earth's crustal deformation and to perform high precision gravimetric assays.
Parent application Ser. No. 08/566,841 filed Dec. 4, 1995 teaches that global positioning satellites can be used to calculate the atmospheric slant path water delay and corresponding integrated water vapor column. According to the parent application, It is first necessary to calculate a position using conventional methods before the slant path water delay can be calculated, but independently obtained tomography profiles and radiometer data can also be used to calculate the slant water path. It has also been discovered that a network of GPS receivers can provide an accurate assessment of slant path water vapor on par with the best data obtainable from modified radiometers with augmentation to eliminate multipath. If anything, the GPS data is even better than the radiometer data because the GPS receivers are less costly and more mobile, and the GPS receivers can perform measurements with a shorter observation window and under all weather conditions.
According to the method and apparatus of the invention, GPS signals from existing satellite-based GPS transmitters are received by standard dual frequency Earth-based GPS receivers in a manner that is well known and practiced in the art. The GPS signals are received at an acute angle relative to the local geometric horizon and are processed in a novel manner that determines the excess path delay of a GPS signal along the elevated propagation path or "slant-path" between a satellite-based GPS transmitter and an Earth-based GPS receiver. The excess path delay is determined from the total refractivity-induced signal delay along the slant-path.
A Slant-path Water Delay ("SWD") measurement technique is based on the principle that electromagnetic radiation such as a radio or microwave transmission is refracted and retarded as it passes through the atmosphere. The refraction causes a "path delay" in the GPS signal. This delay is induced by atmospheric constituents including water vapor. The path delay has a direct relationship to the present atmospheric temperature, pressure, and water vapor local to the slant-path of the GPS signal. Factoring refractivity or SWD measurements into GPS survey measurements enhances the precision that is obtainable from these measurements in positional surveys. Position calculations are more accurate because the SWD is subtracted from the total delay before position is calculated. Thus, precision of the conventional position calculation method is improved by subtracting atmospheric water vapor delays from the total path delay prior to entering the conventional position calculation.
Reliable SWD measurements require exact positioning of high precision transmitters and receivers with stable high frequency signals therebetween. These stable high frequency signals are globally available from any number of existing satellite-based sources including, but not limited to, communications, radio, television, and radar networks. The GPS system is the preferred signal source because it is a highly reliable network of highly stable satellite-based transmitters already in place and designed for complete global coverage. Any other radio transmission source having a known location may be used according to the methodology that is described herein.
A feature of the present invention is to provide a system calibration technique that includes obtaining an independent water vapor measurement local to at least one Earth-based GPS receiver. These independent water vapor measurements can be obtained using a water vapor radiometer or by positioning an Earth-based GPS receiver where there is a known water vapor content, such as a mountain top or desert region. The system calibration can be uploaded to a satellite for transmission to GPS receivers that are capable of using the water vapor measurement to calculate more precise positions, but are separated from any other independent source of water vapor measurements.
In the most preferred embodiment, a plurality of GPS receivers capable of correcting position measurement data for SWD are located at respective receiving-stations that are each fixed in position with respect to the Earth's surface. Suitable means of affixing the receiving stations include bolting the station superstructure to pilings or the like that are driven beneath the Earth's surface, e.g., to bedrock. A plurality of these positionally fixed GPS receiving stations are located in geologically active areas, e.g., along fault lines, areas that exhibit active volcanism, rift zones, overthrust regions or subduction zones. Certain ones of GPS receivers in the network calculate slant water delay where the exact positions of these receivers are known, and these slant path water measurements are averaged for use in position calculations by other GPS receivers in the array.
Fixed GPS receiving stations are placed in areas where the acts of man induce corresponding surface crustal deformations, such as areas where large amounts of geological resources including ore, oil, gas, or water have been removed or injected into naturally occurring reservoirs. In yet other embodiments, fixed GPS-receiving stations are placed proximate nuclear power generation plants or urban areas to monitor in a diagnostic mode the after-effects of earthquakes, or to monitor in predictive fashion crustal deformations that may indicate a need for evacuation. In still other embodiments, a network of GPS receivers is attached to an airplane or truck for use in gravimetric assays to locate ore bodies or petroleum deposits.
FIG. 1 illustrates one Earth-based GPS receiver for making GPS signal measurements from which GPS positions are calculated using corrections for slant water path delay;
FIG. 2 illustrates a receiver array for making multiple simultaneous GPS signal measurements having improved precision with respect to the FIG. 1 embodiment;
FIG. 3 illustrates, in flow diagram form, the steps taken in processing GPS signal measurements to calculate position according to the present invention; and
FIG. 4 illustrates slant water vapor measurements that derive from GPS measurements; and
FIG. 5 illustrates slant water vapor measurements that derive from radiometer measurements.
Radio propagation in the atmosphere is retarded (delayed) by the neutral "dry" atmospheric constituents and by atmospheric water vapor. The total atmospheric delay for radio propagation is conventionally determined from GPS measurements by making a stochastic or least squares estimate of the atmospheric delay to optimize a least squares fit of GPS data in position determination. In this process, a uniform atmospheric distribution is assumed, which results in error due to position calculation measurements that depend on the assumption of azimuthal symmetry in wet refractivity delays when, in actuality, wet refractivity delays are azimuthally variable due to localized differences in atmospheric water content.
Non-idealized atmospheres are not azimuthally symmetric about the Earth-based GPS receiver. On the other hand, conventional GPS calculations correct for atmospheric effects by assuming azimuthal symmetry to calculate a quality which is known as the total zenith delay, and is based upon an idealized vertically propagating radio wave.
This total zenith delay is due to the refractivity N of the total atmosphere integrated along a zenith propagation path to the top of the atmosphere: ##EQU1## where the total zenith delay and dz have units of length in the zenith, and Ntotal is the total refractivity due to the respective dry atmosphere and water vapor refractivity components. Ntotal can be expressed, according to Formula (2), as a function of the local dry and local vapor densities ρdry and ρvapor, R is the ideal gas constant, and T is the local temperature of the water vapor in degrees Kelvin: ##EQU2##
The dry component of zenith delay can be independently measured by determining the total amount of atmosphere above the Earth-based GPS receiver. This determination is accomplished by using a barometer to obtain a barometric pressure measurement local to the receiver. Subtracting the dry component from the total zenith delay yields the delay due to atmospheric water vapor, which is known as the zenith wet delay (ZWD):
ZWD=total zenith delay-zenith dry delay (5)
The zenith wet delay is due to the integrated amount of water vapor along the zenith propagation path: ##EQU3##
The total amount of water vapor along the zenith path is proportional to the ZWD, with a slight dependence upon the temperature of the water vapor. This temperature dependence can be averaged into a mean vapor temperature which can then be correlated to surface measurements of ambient temperature. The PWV is therefore related to ZWD by the following formula:
where II is a weakly temperature dependent dimensionless constant equal to approximately 0.15. II can be estimated to within about 2% from a surface temperature measurement. However, a uniformly stratified atmosphere and azimuthal symmetry is necessarily assumed in the PWV estimation technique; therefore, no spatial structure of the water vapor can be determined.
FIG. 1 illustrates the atmospheric water vapor sensing system of the present invention using the GPS system and one Earth-based GPS receiver to make GPS signal measurements from which excess path delay is determined. Total refractivity due to water vapor is determined from the excess path delay and a specific SWD or SWV measurement can be further determined if desired.
The full GPS network of twenty-one active transmitting satellites and three spares is simplified in the present illustration by showing only five transmitting satellites 120-124 and one receiver 105 on the Earth's surface 100. At any time, receiver 105 can receive simultaneous respective signals 130-134 from the corresponding GPS satellites 120-124. Each signal 130-134 is refracted and retarded as it passes through the Earth's atmosphere 101 due to atmospheric constituents including, but not limited to, water vapor. Atmospheric structure 110 is a cold front moving toward receiver 105 while affecting signal 134.
Receiver 105 is a standard GPS receiver device that is capable of receiving a plurality of simultaneous GPS signals. Specifically, the GPS receiver 105 measures phase angles of each of the radio carriers received which are then processed in a novel manner to determine the excess path delay or SWD in the GPS signal due to the refraction and retardation of the GPS signals 130-134 along the signal's slant-path due to water vapor. The slant-path being measured follows an acute angular "line-of-sight" path through the atmosphere 101 down to a zero angle relative to the geometric horizon, or an angle of slightly less than zero may be obtained due to refraction.
Slant-path GPS signals used for SWD and/or refractivity measurements traverse large sections of the atmosphere thereby facilitating measurements over land and water and significantly increasing the atmospheric water vapor sensing system's spatial resolution. For example, a ten degree slant-path between a GPS transmitter and a receiver relative to the geometric horizon results in a horizontal range of about 34 km through the lower 6 km of the troposphere and the horizontal range of a zero-degree slant path below 6 km is more than 300 km. Because the lower 6 km of troposphere contains approximately 90% of the water vapor in the atmosphere, a single GPS receiver receiving GPS signals from 4 to 12 GPS satellites within its range can sense the distribution of water vapor over a region as large as 600 km diameter.
Signals 130-134 illustrate the refracting of the GPS signals due to atmospheric water vapor generally, and specifically due to atmospheric structure in a GPS signal's path such as cold front 110 for GPS signal 134 or cloud cover 111 for GPS signals 130-133. Factoring the refractivity-induced delay measurements directly into a weather forecasting model reveals valuable information about local, regional, and global atmospheric conditions in the present and future. A refractivity-induced delay is affected by many components including, but not limited to, wet delay, hydrostatic delay, and signal error for each slant-path GPS signal. Specifically, water vapor increases the GPS radio propagation along a slant-path by an amount: ##EQU4## where SWD is the Slant-path Wet Delay along the line-of-sight between the satellite-based GPS transmitter and the Earth-based GPS receiver, SWD and ds have units of distance along the line of sight, and N is defined by equations (2)-(4) above. As a reasonable approximation for satellite elevation angles greater than 20�, SWD is related to ZWD as SWD being approximately equal to ZWD times the cosecant of the elevation angle. SWD is related to SWV by:
where II is a dimensionless conversion factor approximately equal to 0.15. Although II will vary slightly with the elevation angle above the geometric horizon, it can be estimated on average with an accuracy of about 2% based on surface temperature measurements as described above in the zenith case for PWV.
Modeling each GPS receiver's observation in terms of a geometric range such as the observed value minus the computed value, produces the wet delay in the direction of the GPS signal. Because the GPS signal's angular elevation, time sent, time received, range, and time delay are known, the total wet delay along a slant-path can be determined. With each Earth-based GPS receiver typically measuring GPS signals at thirty second intervals from as many as about twelve satellite-based GPS transmitters at one time, thousands of measurements are possible per receiver per day.
In operation, receiver 105 may be used to measure SWD. The SWD measurements are transmitted to GPS satellites, which broadcast the SWD data for position calculation use by other GPS receivers proximal receiver 105. Alternatively, receiver 105 receives SWD data from an independent source, e.g., a network of other GPS receivers that average SWD data over the region where receiver 105 resides, independent tomography profiles that are obtained according to any conventional means, and localized radiometer data.
FIG. 2 illustrates a preferred embodiment of the atmospheric water vapor sensing system 200. FIG. 2 includes all that is disclosed in FIG. 1 with the addition of a receiver array 220 including a plurality of receivers, such as receiver 105. Each Earth-based GPS receiver in a differential receiver array 220 functions as does receiver 105 described in FIG. 1. In contrast to the single receiver system depicted in FIG. 1, the need for knowing the satellite-based GPS transmitter `clock differencing` is resolved because there are multiple receiver references available from which the clock differencing can be determined. Clock errors can be nearly eliminated by a double differencing technique. Specifically, double differencing eliminates GPS transmitter and receiver clock errors, and can be expressed as:
double difference=(φA1 -φB1)-(φA2 -φB2),(11)
where φA1 is the carrier phase observation of satellite 1 from site A on the Earth's surface, φB1 is the carrier phase observation of satellite 1 from site B on the Earth's surface, φA2 is the carrier phase observation of satellite 2 from site A on the Earth's surface, and φB2 is the carrier phase observation of satellite 2 from site B on the Earth's surface.
The above Equation (11) can be written in matrix form to describe a system of N satellites having N-1 differences, i.e., a GPS double difference matrix. The matrix may be inverted to obtain single differences, but the inversion requires a solution of N equations for N-1 differences. Thus, an additional constraint is required to invert the matrix. It has been discovered that an additional constraint may be forced upon the solution to require the average zenith path delay for the system of N satellites to match the average zenith path delay calculated for all of the satellites that are being difference. The resultant single difference can be used for mapping GPS antenna phase center and multipath characteristics where the baseline is less than about 100 meters. The single difference can be used to obtain the differential slant delay between two sites for baselines greater than about 100 meters. Thus, a radiometer at one of the sites in a GPS observation network can be used to determine slant delay at the other sites. The further inversion of GPS single differences can be used to obtain slant path delay, i.e., GPS zero differences.
The preferred receiver array 220 embodiment is a group of densely spaced Earth-based GPS receivers having an improved spatial resolution, as compared to a stand-alone Earth-based GPS receiver 105. The spacing between receivers in receiver array 220 can be random or in a more organized grid configuration. The receiver array 220 in FIG. 2 is neither intended as a minimum nor maximum density of Earth-based GPS receivers. Rather, the receiver array 220 is intended to illustrate that the more densely spaced the receivers, the better the spatial resolution of a defined area. For this reason, the practical number of receivers in receiver array 220 and the physical location of receiver array 220 is determined by the need for higher precision in position measurements. Areas where higher precision can be useful include geologically active areas of the Earth where earthquakes and volcanos are known to occur and, particularly, cities or other heavily populated areas.
A conventional dual frequency GPS receiver is the preferred receiver type for receiver array 220 because the dual frequency feature removes ionospheric delay. Ionospheric delay is another of the total refractivity delay components that must be removed to determine the refractivity due to water vapor. One alternative to using only the relatively expensive dual frequency GPS receivers in receiver array 220 is to use less expensive single frequency GPS receivers, provided that an independent measure of ionospheric delay is available for each single frequency GPS receiver. In other alternatives, the GPS receivers can be placed very close, which permits the use of an assumption that the ionospheric delay is the same at each station. Another alternative to using only the relatively expensive dual frequency GPS receivers in receiver array 220 is to space dual frequency GPS receivers by about 10-50 km in receiver array 220 and fill in the less expensive single frequency GPS receivers therebetween at the density necessary to produce the desired resolution of weather information. One requirement of a receiver array containing both single and dual frequency GPS receivers is that the dual frequency GPS receivers must be spaced at intervals which are smaller than the scale of ionospheric structures that would generate unacceptable error.
Self calibration and absolute tropospheric estimations of atmospheric water delays are possible for receiver array 220 provided there at least two Earth-based GPS receivers separated from each other by at least 500 km. The 500 km requirement is necessary because the elevation angle between any two Earth-based GPS receivers in receiver array 220 and any one GPS transmitter 120-124 would otherwise be nearly indistinguishable. With separation of at least 500 km, ZWD can be computed from barometric pressure and GPS signal measurements alone, according to Formulae (1)-(7).
Other receiver calibration alternatives are available that obtain accurate ZWD estimates within receiver array 220 if receiver separation of less than 500 km exists between at least two Earth-based GPS receivers. A first alternative to the separation requirement is to independently determine for ZWD at least one Earth-based GPS receiver site in receiver array 220 by way of a water vapor radiometer or other water vapor sensing device capable of measuring integrated water vapor with a resolution at or about 1-2 mm. A ZWD estimate can then be obtained based on the difference between the reference site measurements and the second receiver site measurement added to the absolute value of the SWV measure from any Earth-based GPS receiver in receiver array 220.
A final calibration alternative for Earth-based GPS receivers separated by less than 500 km in receiver array 220 is to place at least one Earth-based receiver in a location known to have consistently zero or otherwise stable and known humidity levels and water vapor distributions.
FIG. 3 illustrates the operational steps 300 in flow diagram form for determining excess path delay and SWD. The operational steps 300 begin at step 305 with an operational network of satellite-based GPS transmitters 120-124 (see FIGS. 1 and 2) and at least one operational Earth-based GPS receiver 105 and preferably a receiver array 220 capable of maintaining continuous signal contact with at least one satellite-based GPS transmitter 120-124. The operational steps 300 assume the use of low multi-path GPS receiver antennas and a low multi-path antenna environment. Multi-path is a highly localized error caused by signal reflections from objects located at or near the antenna of a GPS receiver and is often accompanied by receiver antenna phase delay variations that repeat in sidereal time. Objects known to cause multi-path errors include, but are not limited to, the ground below a receiver antenna, trees, buildings, and terrain proximal to the GPS receiver antenna. In practicing the present invention using radiometer-derived SWD measurements, it is important to augment the GPS antennae with ring-shaped collars to reduce multipath. Extreme precision is only obtainable from radiometer data once multipath has been substantially reduced.
The clock offset for each satellite-based GPS transmitter is removed at step 314, e.g., by the double differencing technique of Formula (11). Disparities between transmitter and receiver clocks are also resolved at step 31 to accurately determine signal delay and subsequently the geometric range between the satellite-based GPS transmitter and each Earth-based GPS receiver. Resolving clock differences is important because receiver clock resolution is approximately 10-8 seconds and transmitter clock resolution is approximately 10-13. Even a one nanosecond 10-9 difference in clocks can equal one foot in positioning or an equivalent loss in SWD precision.
The location of an Earth-based GPS receiver such as 105 (see FIGS. 1 and 2) is determined by steps 314-326, based on information available in GPS signals 130-134. High precision positioning is attained by determining the number of carrier wavelengths occurring between an active GPS transmitter and an Earth-based GPS receiver. The wavelength determination includes the integer number of wavelengths that have occurred, and any residual fractional wavelength.
Determining the position of an Earth-based GPS receiver includes compensating for orbital variations of individual satellite-based GPS transmitters, multi-path noise, dry atmospheric delay, and ionospheric refractivity. The preferred technique for these position calculations is that which is incorporated in Bernese software, which is described in Beutler et al, "GPS Software Version 4.0," Univ. Berne, (September, 1996). Other similar programs are commercially available and are available from academic sources at various other universities. These other programs may also be used to practice the invention.
Orbital variation errors for the satellite-based GPS transmitters are reduced by conventional means using orbit predictions or real-time orbit estimations based on published orbit information or triangulation from at least four Earth-based GPS receivers. Conventional alternatives to eliminating multi-path noise include, but are not limited to, improving receiver antenna hardware, and operating the Earth-based GPS receivers in areas that are free of reflective surfaces. Ionospheric delay is eliminated by conventional signal processing because the delay is substantially proportional to the inverse square of the GPS signal's frequency so that the delay is correctable by correlating the two signal frequencies over which a GPS signal is transmitted.
Carrier phase ambiguities are resolved at step 320. A carrier phase ambiguity is the uncertainty in the integer number of wavelengths or carrier cycles occurring in the distance between a satellite-based GPS transmitter and an Earth-based GPS receiver. Resolving carrier phase ambiguity is accomplished according to conventional techniques by observing the time series of GPS observables and determining the integer values that are required to fulfill the distance constraints as each satellite-based GPS transmitter progresses in its respective orbit. Determining the integer value that is required to fulfill the distance constraint plus determining the residual phase angle of the GPS signal's carrier phase yields the radio range between a satellite-based GPS transmitter and an Earth-based GPS receiver.
In step 322, SWV is known from other sources, e.g., radiometer measurements, results from a boundary layer refractivity model, tomography profiles, atmospheric water vapor measurements obtained from at least one other radio receiver and, preferably, combinations thereof. Other GPS receivers in array 200 (see FIG. 2) may use Formula (9) to calculate SWD. This SWD value may be subtracted from the satellite carrier signal propagation time to correct the signal for atmospheric water vapor effects. The GPS SWD measurement times are contemporaneous with the satellite signal propagation times upon which the position calculations are based and, consequently, better reflect atmospheric conditions at the actual time that the position signals are received.
Other methods for obtaining an independent SWD measurement include GPS Doppler observations for refractivity profiling. These observations may be coupled with an atmospheric radiative transfer model, which may be used to train an adaptive filter or neural network to map the doper observations to synthetic SWD measurements. These GPS Doppler measurements are believed to be extremely useful in determining the acceleration of a moving platform, e.g., for use in airborne gravimetry.
Conventional GPS position measurements may be used in conjunction with observations by an accelerometer to obtain SWD from a moving platform. Water vapor causes an apparent acceleration in GPS observations that is not seen by an accelerometer attached to a moving platform. The differences between the acceleration seen using GPS observations and the acceleration measured by the accelerometer can be used to obtain the water vapor affecting the GPS observations.
Step 324 includes determining the radio range, which is the GPS signal distance along the refracted and retarded slant-path between the satellite-based GPS transmitter and the Earth-based GPS receiver. This radio range is determined by conventional means including multiplication of the carrier signal wavelength in vacuum times the integer and residual phase angle that is determined in step 320.
The position of an Earth-based GPS receiver is determined with centimeter accuracy at step 326 using conventional methods established for high-accuracy GPS geodesy. The geometric range along the slant-path between a satellite-based GPS transmitter and an Earth-based GPS receiver is determined at step 328. The geometric range is determined by calculating the straight-line distance between the now-known Earth-based GPS receiver position and the satellite-based GPS transmitter position based upon almanac data including the satellite positions at particular times and corrections for ephemeris errors that are broadcast by the respective satellites.
The excess path length along the slant-path between the satellite-based GPS transmitter and the Earth-based GPS receiver is determined at step 333. The excess path length for any slant-path signal is the difference between the radio range and the geometric range as determined from steps 324 to 328. The total refractivity measurement Ntotal is proportional to the excess path length along the slant-path as determined at step 336, according to Formula (8). Alternatively, SWD can be determined at step 336 based on the excess path length from step 328 by subtracting out the hydrostatic delay determined from a barometric weighing of the atmosphere.
In step 338, SWD is computed based on Formulae (1)-(9). SWD is then subtracted from the total time that was observed for the satellite signal to reach the GPS receiver, e.g., from satellite 120 to receiver 105 in FIG. 2. The subtraction of SWD corrects the signal propagation time for the effects of water vapor. At decision step 350, the system determines whether to repeat the position calculations of steps 320 through 338. Alternatively, step 350 permits the conclusion of the routine at step 353.
A field experiment used radiometer-based atmospheric water vapor measurements to provide a slant water path delay correction for GPS measurements. GPS receivers, radiometers, and barometers were positioned in sites at Platteville and Table Mountain, Colo. The sites chosen for installation of this equipment were relatively free from obstructions above ten degrees elevation and were separated by 43 km. The GPS receivers chosen were Trimble™ SSI GPS receivers equipped with standard 35 cm diameter TurboRogue™ choke ring antennae augmented with 85 cm choke ring collars mounted on pillars of reinforced concrete. The choke ring antennae and collars were provided to reduce multipath. An elevation cutoff angle of 20� was applied to satellite and radiometer measurements. Barometric data accurate to 0.3 mb was logged every minute.
Radiometrics WVR-1100™ radiometers were pointed sequentially towards each GPS satellite in view to observe at 23.8 and 31.4 GHz for one second in the direction of each satellite during an eight minute observation cycle. These measurements based upon blackbody radiation temperatures and conventional water content algorithms produced slant wet delay with an accuracy of 3 mm, according to the method published in Ware et al, "Pointed Water Vapor Corrections for Accurate GPS Surveying," Geophys. Res. Lett., 20 2635-2638 (1993).
The GPS data were analyzed using the commercially available Bernese software described in Beutler et al, "GPS Software Version 4.0, Univ. Berne, (September, 1996) and the International GPS Service precise orbits published in Neilan, "The Evolution of the IGS Global Network, Current Status and Future Prospects, International GPS Service for Geodynamics, 1994 Annual Report, JPL Pub. 95-18, 25-3 (1995). The software utilized double differencing to minimize GPS receiver and transmitter clock errors. Solutions were computed using conventional zenith corrections according to the prior method of Dixon (1991). These solutions were compared to the slant path water delay calculations according to formulae (1) to (9). Radiometer data were interpolated to the GPS observation times at thirty second intervals. Twenty two hours of data were used for daily solutions over eight days in the fall of 1995 and three days in the spring of 1996.
Table 1 below provides the survey precision and offset for the eleven solution days. Slant corrected vertical precision is 1.2 mm, which is a factor of five better than the 6.0 mm obtained using zenith corrections. Similarly, horizontal coordinates improved by a factor of two to sub-mm precision.
TABLE 1______________________________________Slant and Zenith Corrected Precisions for Eleven Solution DaysAtmospheric path delay correction method Vertical North East______________________________________slant (mm rms) 1.2 0.9 0.7 zenith (mm rms) 6.0 1.9 1.6______________________________________
Additionally, the zenith-corrected solutions between different surveys in the fall of 1995 and the spring of 1996 showed significant apparent vertical motion (12.2�4.5 mm) that was not seen in the slant corrected solutions (1.5�1.2 mm). Thus, atmospheric effects are believed to contribute errors in the form of perceived monument stability. This error is much greater for zenith corrected solutions in addition to reduced precision of daily measurements.
FIG. 4 depicts a comparison of typical double difference SWV measurements that were sensed using GPS receivers. FIG. 5 is used for comparison against FIG. 4, and represents SWV measurements taken from a radiometer. The radiometer data and the GPS data closely track one another for each case. According to preferred embodiments, it is possible to use modeling techniques as mapping tools to create a body of data that tracks the radiometer measurements in like manner with the GPS-based SWV measurements that are shown in FIG. 4. For example, a GPS receiver may be used to measure atmospheric boundary layer refractivity, e.g., as between the ionosphere and the troposphere, and conventional adaptive filter or neural network modeling methods are applied in mapping the refractivity data to SWD or SWV. The spikes 420 and 425 on the GPS data curve 415 in FIG. 4 are not observed in the corresponding radiometer curve 515 at positons 520 and 525 because the spikes are smoothed by the 5� beam width and the eight minute sampling interval of the radiometers. Thus, it is apparent that the use of GPS receivers to provide SWD or SWV measurements can be even more accurate than the radiometer data.
The atmospheric water vapor sensing system of the present invention measures refractivity and SWD of slant-path GPS signals transmitted by any one of a plurality of satellite-based GPS transmitters and received by a plurality of Earth-based GPS receivers in a receiver array. Although specific embodiments are disclosed herein it is expected that those skilled in the art can and will design alternative atmospheric water vapor sensing systems that are within the scope of the following claims literally or under the Doctrine of Equivalents.
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Owner name: UNIVERSITY CORPORATION FOR ATMOSPHERIC RESEARCH, C
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:ALBER, CHRIS D.;WARE, RANDOLPH H.;ROCKEN, CHRISTIAN;AND OTHERS;REEL/FRAME:009013/0270;SIGNING DATES FROM 19971222 TO 19971228
|Sep 26, 2003
|Fee payment
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|Sep 19, 2011
|Fee payment
Year of fee payment: 12


text:
Write an Android application
Budjetti $15-25 USD / hour
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Im Steffi. Since March last year I live together with my boyfriend in a lovely flat in Weingarten. I am studying health economics and I am in my final semester now. Before I started to study I did an apprenticeship in Ravensburg, worked there one and a half year and went then to southafrica for one year and did there voluntary work.
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FMS Pitts Biplane 1400mm (55") Wingspan - PNP - SCRATCH AND DENT
FMS 1400mm Pitts Ultimate Sport Bi-Plane - Receiver Ready (PNP) - SCRATCH AND DENT
- Product condition: Customer Return
- Missing parts: See Below
- Damage/defects: Tail wheel has been cut off of the fuselage (pictured). Minor foam imperfections from handling.
This 1400mm FMS Pitts is slightly updated. The servos are now all metal gear so customers don't have to worry about stripped servos during aggressive maneuvers. In addition the spinner has been upgraded to a far more durable 3 piece spinner. We feel these were the two major weak spots in this plane and both have now been addressed.
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text:
I've put some links to the best android math apps i've found so far.
A good calculator, A mini matlab, and a Mathematica.
A truly great calculator: handycalc (much better than all stock and other scientific calculators i've tried)
This also looks awesome (but i have not tried it yet):
Similar to Mathematica (using python): MathScript
Aslak Grinsted > Misc. Debris >


text:
Paul Ferguson has one selection for us on Monday; Oscara Dara in the 1.00 at Plumpton. Compare odds and bet.
Though stable-mate Malt Master failed to advertise the form of his Punchestown Festival win when beaten at Bangor on Friday Oscara Dara (1:00) is still fancied to make a winning chase debut in Plumpton's SIS Live Novices' Chase on Monday.
That victory had come on just his third start over hurdles, having previously won on debut at Sandown (by 20 lengths) and having finished fourth behind stable-mates Darlan and Captain Conan in the Grade 2 Top Novices' Hurdle at Aintree.
Today's jockey David Bass rode him at both Sandown and Aintree, so he knows the horse well and he had earlier shown smart bumper form for Alan Fleming, when winning at Southwell and chasing home another of his current stable-mates, the well regarded Mono Man, in a decent event at Ascot.
He proved he handles testing ground at Punchestown and he is given the nod over Cantlow who continues to run over a trip shorter than ideal; he's been crying out for a step up 2m4f or further since going chasing, though he has run well in defeat on both starts to date. The selection opened up at 8/11 with Paddy Power on Monday morning
Monday's selection:
1:00 Plumpton: Oscara Dara (8/11 Paddy Power)
Compare all today's horse racing odds and bet at the best prices
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- PALACE JESTER – 14/1 winner at FFos Las
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recipe for children's parties …
200 gr flour
30 g cornflour
170 g butter
50-60 grams of powdered sugar
little vanilla
Sift flour and starch. Beat 170 grams slightly softened butter with powdered sugar and vanilla. Add the flour and knead a soft dough.
The dough is divided into parts. Add to each part of the food colors to choose from and knead.
Pinch off a piece, roll the ball, forming a ball with your fingers a button. Now make "bumpers" buttons with the help of nozzles. A wooden skewer make a hole. Buttons can be dipped into sugar – for a change …. Bake at 150 ° C – 10-15 minutes.


text:
Archinect - News 2017-07-23T12:33:48-04:00 http://archinect.com/news/article/150010337/ww-p-designed-school-opens-in-cambodia WW+P-Designed School Opens in Cambodia Weston Williamson 2017-06-02T01:03:00-04:00 >2017-06-01T14:14:53-04:00
A new school in rural Cambodia, designed and built pro-bono by Weston Williamson + Partners officially opens on June 1, International Children's Day.

WW+P worked with Engenuiti, Integration and Building Trust International to design a building which was flexible and adaptable to meet current and future needs. It comprises three additional classrooms, a library and a covered external classroom with a sunken play area, which doubles as a small amphitheatre.

Until now the school in Khyaung village, 40km north east of Phnom Penh City, has catered for 359 pupils aged 3-17 in two old buildings. The lack of accommodation has meant that children travelling from six surrounding villages to this, the area's only school catering for children up to secondary age, had to attend in shifts, part-time.

From February to April this year, a team of designers from WW+P's London studio led by architect Abul Mahdi, assisted the local farming community with the construction on a two-week rotation. The tea...
 http://archinect.com/news/article/149982777/which-news-stories-defined-architecture-education-in-2016 Which news stories defined architecture education in 2016? Amelia Taylor-Hochberg 2016-12-15T12:33:00-05:00 >2016-12-21T22:08:23-05:00
In education and academia news, 2016 had its fair share of architecture's everlasting debate over Theory v. Practice, while also making a big move towards improving students' rights. Check out our most significant News stories from the world of architecture school in 2016:

Peter Zellner to launch the Free School of Architecture, a tuition-free, experimental architecture school

The FSA is a tuition-free post-graduate school in Los Angeles, to be launched in 2017. While free, the school won't be accredited, nor based in a static location, and also be capped at 48 students by 2020 – characteristics that commentators were critical of, for concern it could turn into a pure ideas salon. Zellner aligned the school with the radical pedagogical departures taken by Ray Kappe at SCI-Arc and Peter Eisenman at the IAUS.

Following a landmark decision, graduate students will now be able to unionize

The decision overturned a 2004 precedent set by the National Labor Relations Board, that determined stud...
 http://archinect.com/news/article/149974707/ten-top-images-on-archinect-s-new-learning-spaces-pinterest-board Ten Top Images on Archinect's NEW "Learning Spaces" Pinterest Board Archinect 2016-10-21T17:37:00-04:00 >2016-11-02T23:10:23-04:00
In case you haven't checked out Archinect's Pinterest boards in a while, we have compiled ten recently pinned images from outstanding projects on various Archinect Firm and People profiles.

(Tip: use the handy FOLLOW feature to easily keep up-to-date with all your favorite Archinect profiles!)

Today's top images (in no particular order) are from the brand new board Learning Spaces.

↑ Energy Positive Relocatable Classroom in Ewa Beach, HI by Anderson Anderson Architecture; Photo: Anthony Vizzari, Anderson Anderson Architecture

↑ Khabele Elementary Expansion in Austin, TX by Derrington Building Studio; Photo: Peter Molick Photography

↑ Eemhuis in Amersfoort, the Netherlands by Neutelings Riedijk Architects; Photo: Scagliola/Brakkee © Neutelings Riedijk Architects

↑ Florida Polytechnic University in Lakeland, FL by Santiago Calatrava; Photo: Julian Parkinson

↑ Academy of Art & Architecture in Maastricht, the Netherlands by Wiel Arets Architects

↑ Fladängskolan in Lomma, Sweden by Link Arkitekt...
 http://archinect.com/news/article/149960972/environmentally-friendly-design-inspires-education-at-howe-dell-primary-school Environmentally-friendly design inspires education at Howe Dell Primary school Jessica Bonehill 2016-08-02T05:06:00-04:00 >2016-08-09T01:00:18-04:00
Howe Dell Primary in Hatfield could well be the UK's most eco-friendly school. It has toilets that flush using rainwater, sedum roofs made of plants and vegetation, and classroom sink-tops made from recycled yoghurt pots. But the school's design doesn't just help protect the environment, it also uses nature to improve children's academic performance and behaviour.

Howe Dell Primary's £10 million, eco-friendly design is used by teachers to promote sustainability to a new generation of pupils. Capita Architects were given free reign to push the limits of sustainable design in the project, which was funded by the council, and that was exactly what they did. The school features solar panels, a wind turbine, and a heating system that uses a series of pipes just below the surface of the school playground for passive gain that is then utilised to heat the school.

This groundbreaking design was awarded ECO Green Flag accreditation (the highest level awarded to sustainable schools in the UK) and places pupils in close proximity to nature. To this end, the design's wetland area and sedum roofs are used to study birds and the school places sustainability at the core of the curriculum. This learning is even extended to the playground where learning stations allow pupils to examine the habitats of micro-beasts. In this way, the whole building is understood...
 http://archinect.com/news/article/116039165/chinese-art-institute-resembles-hogwarts-castle Chinese art institute resembles Hogwarts Castle Alexander Walter 2014-12-15T14:06:00-05:00 >2014-12-18T20:19:40-05:00
The Hebei Academy of Fine Arts in China's Hebei Province has constructed a new campus in Xinle City that, rather than resembling local architecture, adheres more to Gothic and European styles. Specifically, it bears a striking resemblance to the Hogwarts School of Witchcraft and Wizardry. [...] But the new building is actually called "Cinderella's Castle," and was modeled on structures from medieval Europe. Unfortunately, the building has little to do with Cinderella or Hogwarts.

Previously: Chinese Colleges Are Trying to Look Like the Ivy League
 http://archinect.com/news/article/116035941/wright-architecture-school-sets-fund-raising-goal-for-independence Wright Architecture School Sets Fund-raising Goal for Independence Alexander Walter 2014-12-15T13:12:00-05:00 >2014-12-15T13:13:00-05:00
The architecture school run by the Frank Lloyd Wright Foundation will try to raise $2 million before the end of 2015 to ensure its future as an independent organization, the foundation announced on Monday, having approved a possible path toward the school's incorporation. [...] The foundation's board had initially decided not to incorporate the school separately, for fear of losing control over its operations. But objections from school supporters prompted the board to reconsider.

Previously: New Plan for Architecture School at Wright Foundation
 http://archinect.com/news/article/113498244/frank-gehry-at-uts-a-first-look-inside-dr-chau-chak-wing-building Frank Gehry at UTS: a first look inside Dr Chau Chak wing building Alexander Walter 2014-11-12T14:05:00-05:00 >2015-02-03T12:14:59-05:00
Architect Frank Gehry courts curves and controversy, and the deputy vice-chancellor of UTS admits to a degree of trepidation. A first look inside reveals whether those fears were justified [...] The city's first building by the controversial architect is part of a larger $1.1bn masterplan for the University of Technology Sydney (UTS), but is already attracting a lot of attention.

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd"> <meta> http://archinect.com/news/article/112573293/new-plan-for-architecture-school-at-wright-foundation New Plan for Architecture School at Wright Foundation Alexander Walter 2014-10-31T15:00:00-04:00 >2014-11-05T20:16:38-05:00
The Frank Lloyd Wright Foundation has approved a possible path toward independent incorporation of its architecture school – providing fund-raising targets are met, Sean Malone, the foundation's president and chief executive, said in a note sent Wednesday evening to people involved in the school.

Previously: Spiralling Tensions at Frank Lloyd Wright Architecture School
 http://archinect.com/news/article/107634526/norwegian-artists-plan-to-open-art-academy-in-north-korea Norwegian artists plan to open art academy in North Korea Alexander Walter 2014-08-28T13:20:00-04:00 >2014-08-28T16:49:57-04:00
The North Korean government has approved plans by two Norwegian artists to open an art academy in the country. Henrik Placht and Morten Traavik travelled to North Korea together for the first time in August to flesh out the proposal and to look for potential sponsors. So far they have received financial support from the Prince Claus Fund. [...] "One of the reasons for us going to North Korea is that we don't believe in sanctions and the boycott of art," Placht tells The Art Newspaper.

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd"> <meta> http://archinect.com/news/article/107571089/spiralling-tensions-at-frank-lloyd-wright-architecture-school Spiralling Tensions at Frank Lloyd Wright Architecture School Alexander Walter 2014-08-27T17:36:00-04:00 >2014-10-31T15:01:12-04:00
The architecture school run by the Frank Lloyd Wright Foundation on Wednesday criticized a decision by the foundation's board that will result in the school losing its accreditation. Last week, the Higher Learning Commission, a Chicago-based nonprofit that accredits universities and colleges, told the school it would lose its accreditation in 2017.

Previously: Taliesin faces loss of accreditation, suspends fall enrollment

UPDATE: New Plan for Architecture School at Wright Foundation
 http://archinect.com/news/article/103934627/architecture-at-london-s-royal-academy-of-arts-summer-exhibition-2014 Architecture at London's Royal Academy of Arts - Summer Exhibition 2014 Alexander Walter 2014-07-11T12:41:00-04:00 >2014-10-03T09:29:44-04:00
Got a day to spend in London this summer? Go and immerse yourself in the Royal Academy of Arts' Summer Exhibition 2014 which opened to the public last month. The annual event — held every year without interruption since 1769 — prides itself as the world's largest open submission exhibition. The program aims to provide an international platform for emerging and established artists in various disciplines ranging from painting to printmaking, photography, sculpture, architecture and film.

The Summer Exhibition 2014 will be on display until Sunday, August 17.
 http://archinect.com/news/article/102169777/in-detroit-a-groundbreaking-school-comes-back-as-condos In Detroit, a Groundbreaking School Comes Back as Condos Amelia Taylor-Hochberg 2014-06-18T13:39:00-04:00 >2014-06-23T22:13:17-04:00
Due to plummeting enrollment and a troubled district, vacant school buildings—heck, just vacant buildings—are none too rare in Detroit. After 19 years of abandonment, the Nellie Leland School, however, is no longer vacant—it, as abandoned urban buildings are want to do, is back in session as condos. [...] Today, the school is known as Leland Lofts, a set of expansive condos in the Lafayette Park neighborhood near downtown Detroit, where a 1,465-square-foot, one-bedroom loft goes for $175K.

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd"> <meta> http://archinect.com/news/article/101575299/30-weeks-an-experimental-new-design-school-backed-by-google 30 Weeks: An Experimental New Design School, Backed By Google Archinect 2014-06-10T20:30:00-04:00 >2014-06-17T17:34:04-04:00
Following Apple's success, many companies are finally starting to recognize the crucial role design plays in building a desirable (and profitable) product. Yet very few companies are actually founded and led by designers. Here to change that is 30 Weeks, a new program by a powerhouse team of New York design schools--Parsons, Pratt, School of Visual Arts, and The Cooper Union--in collaboration with the education company Hyper Island and Google.

The 30-week program will operate out of a coworking space in Dumbo, Brooklyn. Twenty students will be invited to participate. The only requirements are that they're designers 18 or older and have an idea for a product.

Interested? Apply here.
 http://archinect.com/news/article/100643988/salvage-starts-at-fire-ravaged-glasgow-school-of-art Salvage starts at fire-ravaged Glasgow School of Art Alexander Walter 2014-05-29T18:01:00-04:00 >2015-02-10T13:16:43-05:00
The GSA said that retrieving the archives and collections from inside the building was its "first priority". [...] Firefighters were able to save around 70 per cent of the Charles Rennie Mackintosh-designed building's contents during the blaze. But the famed Mackintosh library, which contained hundreds of rare periodicals and collections, was destroyed, along with countless works of art and the roof of the west wing.

Previously:

Glasgow School of Art on fire....

UPDATE: Glasgow School of Art fire

 http://archinect.com/news/article/100285007/update-glasgow-school-of-art-fire UPDATE: Glasgow School of Art fire Archinect 2014-05-23T13:23:00-04:00 >2017-06-14T14:04:52-04:00
Today's tragic developing story is the massive fire engulfing the historic Glasgow School of Art building, the masterpiece by Scottish architect Charles Rennie Mackintosh.

News updates and tweets (#gsafire) are pouring in left and right, and we'll try to collect the latest developments in this post.

Tweets about "#gsafire"
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The Glasgow School of Art Media Centre tweets a link to this Statement from Muriel Gray, Chair of Board of Governors on fire at the Mack:

"Today is a really black one for the GSA, but I cannot thank the fire brigade enough for the speed with which they came and their commitment to contain and extinguish the fire.

Fortunately there have been no fatalities or injuries.

I am so proud of the sta...
 http://archinect.com/news/article/96101073/in-new-sandy-hook-school-newtown-plays-design-role In New Sandy Hook School, Newtown Plays Design Role Alexander Walter 2014-03-20T14:11:00-04:00 >2014-03-27T03:13:15-04:00
The school will be in the woods, away from the parking lot. It will feature a long, curving corridor that the architect likens to arms embracing students as they enter. [...] The architects the town chose, Svigals + Partners, a 30-person firm based in New Haven, had only a half-dozen elementary schools in its portfolio, far fewer than bigger competitors for the commission. It was known as well for designing laboratories for Yale and high-end houses for celebrities

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd"> <meta> http://archinect.com/news/article/94350054/at-boston-latin-school-urban-planning-101-from-the-pros At Boston Latin School, urban planning 101 from the pros Archinect 2014-02-25T15:38:00-05:00 >2014-03-03T21:00:41-05:00
Wendy Holm, the Boston Latin teacher who has incorporated Urban Plan into her economics courses, said it combines basic concepts she has taught her students with something very close to a real-world context. "One of the goals that the Urban Land Institute has is that kids come out of this experience and through it have this broader view, then, of this kind of experience and take it into their adult life," said Holm.

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd"> <meta> http://archinect.com/news/article/90613723/bummer-ny-fed-reserve-reports-high-unemployment-rates-for-recent-architecture-grads Bummer: NY Fed Reserve reports high unemployment rates for recent architecture grads Amelia Taylor-Hochberg 2014-01-06T18:34:00-05:00 >2014-01-13T20:24:46-05:00
The New York Federal Reserve's latest research report discusses a number of difficulties facing recent college graduates, including unemployment. [...] After dividing the pool into 13 different undergraduate majors, and using data from 2009 to 2011, some academic pursuits proved likelier to land graduates a job. [...] For instance, the unemployment rate for architecture and construction majors was 8%, likely related to the fate of housing-related sectors following the housing bust.

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd"> <meta> http://archinect.com/news/article/90049524/solving-problems-for-real-world-using-design Solving Problems for Real World, Using Design anthony dong 2013-12-30T13:57:00-05:00 >2014-01-06T19:30:04-05:00
While the projects had wildly different end products, they both had a similar starting point: focusing on how to ease people's lives. And that is a central lesson at the school, which is pushing students to rethink the boundaries for many industries. At the heart of the school's courses is developing what David Kelley, one of the school's founders, calls an empathy muscle.

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd"> <meta> http://archinect.com/news/article/86918913/rogers-stirk-harbour-partners-wins-lse-global-centre-for-social-sciences-competition Rogers Stirk Harbour + Partners wins LSE Global Centre for Social Sciences competition Justine Testado 2013-11-19T15:46:00-05:00 >2013-11-19T17:55:20-05:00
Rogers Stirk Harbour + Partners has just been revealed as the winner of the RIBA and London School of Economics competition to design the LSE's New Global Centre for Social Sciences. Rogers Stirk Harbour won the £90 million (US$145M) project against finalists OMA (The Netherlands); Grafton Architects (Ireland); Heneghan Peng (Ireland); and Hopkins Architects (UK).

 Previously: Can you guess the 5 finalist teams of the LSE Global Centre for Social Sciences Competition?

 Images courtesy of RIBA - LSE New Global Centre for Social Sciences competition.
 http://archinect.com/news/article/86543159/agi-architects-wins-in-two-categories-for-2013-middle-east-architect-awards AGi architects wins in two categories for 2013 Middle East Architect Awards Justine Testado 2013-11-14T19:02:00-05:00 >2013-11-14T19:05:55-05:00
AGi architects enjoyed yet another lucky year in the 2013 Middle East Architect Awards recently held in Dubai. In addition to being shortlisted in five categories, the Spanish-Kuwaiti firm won two awards for The Star House and the BBS Pre-School, both in Kuwait. The Star House received Residential Project of the Year — making it the second year in a row that AGi won in the category — while the BBS Pre-School was named Institutional & Cultural Project of the Year.

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd"> <meta> http://archinect.com/news/article/86397607/now-accepting-applications-one-of-the-only-naab-accredited-m-arch-programs-online Now Accepting Applications: One of the Only NAAB-Accredited M.Arch Programs Online! Sponsor 2013-11-13T11:02:00-05:00 >2013-11-13T12:12:53-05:00
 This post is brought to you by Lawrence Technological University:

 Lawrence Technological University is now accepting applications for its online Master of Architecture program.

 Provided by one of the oldest and largest schools of architecture in the country, LTU's M.Arch degree is built with practicing industry professionals in mind. LTU's flexible online coursework represents a unique opportunity for those looking to round out their existing portfolio with more formal academic training – all while building the qualifications necessary to sit for the NCARB exam.

 Program At-a-Glance:

 One of the few online programs accredited by NAAB

 Can be completed in as little as 15 months

 Flexible structure attractive for working professionals

 Competitively priced

 Our application deadline is quickly approaching, but there's still time.

 Learn more by clicking here!
 http://archinect.com/news/article/80140628/five-projects-receive-the-aia-s-2013-educational-facility-design-excellence-award Five Projects receive the AIA's 2013 Educational Facility Design Excellence Award Justine Testado 2013-08-23T13:16:00-04:00 >2013-09-20T09:41:57-04:00
The Committee on Architecture for Education (CAE) of The American Institute of Architects honored five educational and cultural projects for the CAE Educational Facility Design Excellence Award on Aug. 7. The Educational Facility Design Awards jury selected the projects they perceived as exemplary learning spaces that further the client's educational programs and goals as well as exhibiting outstanding architectural design.

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd"> <meta> http://archinect.com/news/article/79000635/behnisch-architekten-completes-john-and-frances-angelos-law-center-for-the-university-of-baltimore Behnisch Architekten Completes John and Frances Angelos Law Center for the University of Baltimore Justine Testado 2013-08-08T18:13:00-04:00 >2013-08-14T11:55:45-04:00
Behnisch Architekten, in collaboration with Ayers Saint Gross, completed the John and Frances Angelos Law Center for the University of Baltimore this past April. The structure began construction in 2009 after the firm, which was developed under the leadership of Günter Behnisch's son Stefan, won first place in the university's international design competition back in 2008.

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd"> <meta> http://archinect.com/news/article/77844999/verstas-architects-saunalahti-school-exemplifies-finnish-school-architecture VERSTAS Architects' Saunalahti School Exemplifies Finnish School Architecture Alexander Walter 2013-07-24T19:07:00-04:00 >2013-07-25T02:18:49-04:00
Helsinki-based VERSTAS Architects has shared with us the beautiful Saunalahti Comprehensive School project in Espoo, Finland's second largest city. The school building, completed last fall, was the result of an open architecture competition in 2007 which VERSTAS Architects won.

 At the core of the design process for Saunalahti School stood the question of, primarily, how the physical school environment effects the learning results, and secondly, if a school building could also serve the larger audience as well. – Crucial thoughts considering the continuously highest ranking of Finnish education in international comparison.
 http://archinect.com/news/article/76756277/3xn-to-design-university-building-in-stuttgart-germany 3XN to Design University Building in Stuttgart, Germany Alexander Walter 2013-07-10T16:21:00-04:00 >2013-08-07T09:06:14-04:00
[...] the Danish architects have been announced winners of the invited competition for a new building for German university Duale Hochschule Baden-Württemberg in Stuttgart. A total of 25 companies were invited to compete, more than 130 had applied for prequalification.

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd"> <meta> http://archinect.com/news/article/75977995/bamboo-lakou-wins-the-architectural-association-s-2013-foster-partners-prize 'Bamboo Lakou' Wins the Architectural Association's 2013 Foster + Partners Prize Alexander Walter 2013-06-27T17:29:00-04:00 >2013-07-01T18:54:18-04:00
London's Architectural Association School of Architecture and Foster + Partners have announced the winner of the 2013 Foster + Partners Prize, presented annually to the AA diploma student whose portfolio best addresses the themes of sustainability and infrastructure. The recipient is selected jointly by the AA and Foster + Partners at the end of each academic year. This year's prize has been awarded to John Naylor, of Diploma Unit 16, for his project 'Bamboo Lakou'.

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd"> <meta> http://archinect.com/news/article/71506057/big-s-marknagil-education-center-breaks-ground-on-faroe-islands BIG's Marknagil Education Center Breaks Ground on Faroe Islands Alexander Walter 2013-04-18T21:31:00-04:00 >2013-04-22T18:27:19-04:00
It seems to be big groundbreaking week for Danish firms right now: yesterday we reported about schmidt hammer lassen architects kicking off construction of their enormous International Criminal Court campus in The Hague, The Netherlands, and now we're also hearing of BIG breaking ground on the Marknagil Education Center—soon to become the biggest building on the Faroe Islands.

 Together with local architects Fuglark and a team of consultants, BIG had won the competition for the 19,200 sqm / 206,667 sq ft educational facility back in 2009.
 http://archinect.com/news/article/69781257/the-stern-designed-kohler-environmental-center-forces-students-to-work-with-their-zero-energy-building The Stern-designed Kohler Environmental Center forces students to work with their zero-energy building Archinect 2013-03-20T17:53:00-04:00 >2013-03-25T20:34:19-04:00
The students were tapped in determining whether to invest in one or two clothes dryers. Would they use drying racks to eliminate the second dryer? Would they give up hair dryers? Would they wear sweaters in winter to permit an energy-saving thermostat setting of 67 degrees? "We don't tell students that certain behaviors are unacceptable," said Joseph Scanio, one of the center's two live-in teachers. "We discuss things. We make it easy to be intentional about the choices you make."

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd"> <meta> http://archinect.com/news/article/68391010/sky-is-far-from-limit-in-nasa-architecture-project Sky is far from limit in NASA architecture project Archinect 2013-02-26T14:42:00-05:00 >2013-03-06T20:33:27-05:00
A new partnership with the National Aeronautics and Space Administration brings an out-of-this-world opportunity for Cal Poly Pomona architecture students. Over the past months, students have been constructing a massive 30 foot structure in the parking lot of the Interim Design Center. [...] The scenario given by NASA was to build a vertical habitat facility for four astronauts that can go into deep space for 60 days.

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd"> <meta>


text:
Boring is the New AwesomeSP360: Service Provider
The core principle of model-driven telemetry is super simple: as much usable data out of the network as fast as possible. The implementation is also pretty subtle: a push mechanism,Read More
Oh, How Far We've Come in Building Cloud-Scale NetworkingSP360: Service Provider
It's been a year since I wrote this blog detailing our software innovations aimed at helping Service Providers address the ever-increasing challenges imposed by digitization. IOS XR for cloud-scale networkingRead More
What's So Special About Model-Driven Telemetry?SP360: Service Provider
Telemetry and analytics are all the rage in networking today. The industry is abuzz with the potential unlocked by streaming vast quantities of operational data. But what's so special aboutRead More
The limits of SNMPSP360: Service Provider
Not "New Data" But "New Ways of Getting Data" Model-driven telemetry has been one of the most fun projects I've worked on in a long time. Right from the start,Read More
Is SNMP here forever or could it vanish sooner than expected?SP360: Service Provider
The first SNMP release came out in 1988. 28 years later, SNMP is still around… Will this still be the case in 10 years from now? Difficult to say butRead More
Telemetry & Gaining Web Scale Operational Efficiency – Is it a Myth or Reality?SP360: Service Provider
We can't express how excited we were when Cisco was asked to sponsor and participate in an independent event, hosted by Tech Field Day, which invited experts from NetFlix, Google,Read More


text:
Anyone ever come across an issue where the default retention for all mailboxes is say 30 days..but you create another tag for 100 days lets say. All is working fine, till one day a user points out that the retention on what should've been 100 days says 30, sure enough i check that one particular email account and its the default 30 days.
Any thoughts on what would do that? MS patch / reboot? Other policies are in place fine, can't specify exactly when it started happening as it wasn't reported and i am also not the admin. I did however create and test the retention so i'm positive that was working.
5 Replies
Jun 4, 2012 at 3:18 UTC
Retention policies are set per user, could you admin be applying a different policy to users than the one you created?
Jun 4, 2012 at 3:23 UTC
no the same thing happened to a mailbox he applied it too and he has no explanation for it. The "30" day one is default for all mailboxes (new ones created and all) the "100" day one was created and applied separately to 3 mailboxes. Just one day they got the "30" day one, neither of us can figure why.
Jun 4, 2012 at 4:14 UTC
Can't say it's happened here, we have a 21 day policy on all but a handful of people who have no retention policy. And I'm sure I'd hear about it if it did happen...
Jun 5, 2012 at 2:14 UTC
It sounds like the mailbox lost its retention policy and reverted back to the default of 30.
Jun 5, 2012 at 2:25 UTC
How does the mailbox "lose" its retention policy? so i can look for it in the future
This discussion has been inactive for over a year.
You may get a better answer to your question by starting a new discussion.


text:
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