I have a layer in GeoServer and its projection is EPSG:27700. When I query the layer in my app I get and error.  Explanation:  The GeoServer preview displays it correctly. So I copy the JavaScript from the OpenLayers preview page of the layer and use it in my map, and then I compare the browser console for network requests. My map sends an SRS parameter of EPSG:3857 in its requests, whereas the GeoServer preview sends an SRS parameter of EPSG:27700 in it's requests. When I copy the request and past it into the browser I get a WMS file with this seemingly unrelated error message:  Error rendering coverage on the fast path java.lang.IllegalArgumentException: The reference geometry must be either Polygon, MultiPolygon, or a polygonal PreparedGeometry The reference geometry must be either Polygon, MultiPolygon, or a polygonal PreparedGeometry   If I manually modify the SRS value in the URL and paste it into the browser again... I get a valid png file.  I assume the SRS it is sending is identifying what the projection of the map object and I cannot change it? Can anyone help me to understand what is going on please?  === marked as duplicate, although the question linked doesn't help me much === By "copy the request" I meant that Using the browser console I copied the URL my map was firing to GeoServer to request tiles.  The only difference between what my map's URL and the URL from the GeoServer's OpenLayers preview is that the SRS parameter is different.  The GeoServer preview request gets a valid png, the request from my map results in the error mentioned. I guess specifically I want to understand how that results in the error as I cannot understand how referencing a geometry even comes into this scenario.
I am trying to incorporate a wms feed in the British national grid projection (EPSG:27700) into a openlayers 3 project. I initially had used this wms layer in an openlayers 2 application using the following syntax:  new OpenLayers.Layer.WMS(         "ukimage",         "http://www.linktowms",         {             "LAYERS": 'ukimage',             "STYLES": '',             format: state.image_format         }, {     buffer: 0,     displayOutsideMaxExtent: true,     isBaseLayer: true } );   But I am having trouble converting this over to openlayers 3. I first tried setting the map projection to British national grid (view: new ol.View({ projection: 'EPSG:27700'}) as I had in the openlayers 2 app, but this produced the error  TypeError: h.B is not a function    and a white map.   When I try and use proj4 to convert the projection to EPSG:3857 as described here:  I get the same error:   TypeError: h.B is not a function    and again a white map.   my wms request is generally a varient of:  new ol.layer.Image({       source: new ol.source.TileWMS({         url: 'http://www.linktowms',         params: {'LAYERS': 'ukimage'},       })     }),   (I tried adding projection but that didn't help)  I am trying to work out if the image is even getting loaded from the WMS feed, but the syntax seems to have changed significantly from openlayers 2, instead of the properties and functions that have rather descriptive names, there are a now lots of short functions with names like Ua and Ig, which leaves me a bit in the dark as to what's actually going on when I try and inspect the layer with firebug.  I don't mind what projection the application is in, as I can re-project my other layers to match the basemap, so basically any way of using this EPSG 27700 WMS layer in openlayers 3 would be great.
Quotient ring of Gaussian integers $\mathbb{Z}[i]/(a+bi)$ when $a$ and $b$ are NOT coprime The isomorphism $\mathbb{Z}[i]/(a+bi) \cong \Bbb Z/(a^2+b^2)\Bbb Z$ is , when the integers $a$ and $b$ are coprime. But what happens when they are not coprime, say $(a,b)=d&gt;1$?      — For instance if $p$ is prime (which is not coprime with $0$) then $$\mathbb{Z}[i]/(p) \cong \mathbb{F}_p[X]/(X^2+1) \cong \begin{cases} \mathbb{F}_{p^2} &amp;\text{if } p \equiv 3 \pmod 4\\ \mathbb{F}_{p} \times \mathbb{F}_{p} &amp;\text{if } p \equiv 1 \pmod 4 \end{cases}$$ (because $-1$ is a square mod $p$ iff $(-1)^{(p-1)/2}=1$).  — More generally, if $n=p_1^{r_1} \cdots p_m^{r_m} \in \Bbb N$, then  each pair of integers $p_j^{r_j}$ are coprime, so that by CRT we get $$\mathbb{Z}[i]/(n) \cong \mathbb{Z}[i]/(p_1^{r_1}) \times \cdots \times \mathbb{Z}[i]/(p_m^{r_m})$$  I was not sure how to find the structure of $\mathbb{Z}[i]/(p^{r}) \cong (\Bbb Z/p^r \Bbb Z)[X] \,/\, (X^2+1)$ when $p$ is prime and $r&gt;1$.  — Even more generally, in order to determine the structure of $\mathbb{Z}[i]/(a+bi)$ with $a+bi=d(x+iy)$ and $(x,y)=1$, we could try to use the CRT, provided that $d$ is coprime with $x+iy$ in $\Bbb Z[i]$. But this is not always true: for $d=13$ and $x+iy=2+3i$, we can't find Gauss integers $u$ and $v$ such that $du + (x+iy)v=1$, because this would mean that $(2+3i)[(2-3i)u+v]=1$, i.e. $2+3i$ is a unit in $\Bbb Z[i]$ which is not because its norm is $13 \neq ±1$.  — I was not able to go further. I recall that my general question is to known what $\mathbb{Z}[i]/(a+bi)$ is isomorphic to, when $a$ and $b$ are integers which are not coprime (for instance $a=p^r,b=0$ or $d=(a,b) = a^2+b^2&gt;1$).  Thank you for your help! Why is it that many of the most important physical equations don't have ugly numbers (i.e., "arbitrary" irrational factors) to line up both sides?   Why can so many equations be expressed so neatly with small natural numbers while recycling a relatively small set of physical and mathematical constants?  For example, why is mass–energy equivalence describable by the equation $E = mc^2$ and not something like $E \approx 27.642 \times mc^2$?  Why is time dilation describable by something as neat as $t' = \sqrt{\frac{t}{1 - \frac{v^2}{c^2}}}$ and not something ugly like $t' \approx 672.097 \times 10^{-4} \times \sqrt{\frac{t}{1 - \frac{v^2}{c^2}}}$.  ... and so forth.    I'm not well educated on matters of physics and so I feel a bit sheepish asking this.   Likewise I'm not sure if this is a more philosophical question or one that permits a concrete answer ... or perhaps even the premise of the question itself is flawed ... so I would gratefully consider anything that sheds light on the nature of the question itself as an answer.    EDIT: I just wished to give a little more context as to where I was coming from with this question based on some of the responses:  @Jerry Schirmer comments:      You do have an ugly factor of $2.997458 \times 10^8 m/s$ in front of everything. You just hide the ugliness by calling this number c.   These are not the types of "ugly constants" I'm talking about in that this number is the speed of light. It is not just some constant needed to balance two side of an equation.  @Carl Witthoft answers:      It's all in how you define the units ...   Of course this is true, we could in theory hide all sorts of ugly constants by using different units on the right and the left. But as in the case of $E=mc^2$, I am talking about equations where the units on the left are consistent with the units on the right, irrespective of the units used. As I mentioned on a comment there:     $E=mc^2$  could be defined using units like $m$ in imperial stones ($\textsf{S}$), $c$ in cubits/fortnight ($\textsf{CF}^{−1}$) and $E$ in ... umm ... $\textsf{SC}^2\textsf{F}^{−2}$ ... so long as the units are in the same system, we still don't need a fudge factor.   When the units are consistent in this manner, there's no room for hiding fudge constants. How can I get a shapefile from a postgis query? Functional equation $f(r \cos \varphi)+f(r \sin \varphi)=f(r)$ Find all such monotonous function $f:[0,+\infty)\to \mathbb R$, such that for any real $r\ge0$ and $\varphi \in \left[\frac{\pi}6, \frac{\pi}4\right]$, $$f(r \cos \varphi)+f(r \sin \varphi)=f(r)\text.$$  My work so far:  If $\varphi \in \left[\frac{\pi}6, \frac{\pi}4\right]$ then $$\frac{\sqrt2}2\le\cos \varphi\le\frac{\sqrt3}2$$ $$\frac12\le\sin \varphi\le\frac{\sqrt2}2$$  If $r=0$ then $f(0)=0$  If $\varphi= \frac{\pi}{4}$ then $$f(r)=4f\left(\frac r2\right)$$  $f(x)=cx^2$ for $x\ge0$ and $c\in\mathbb R$ Why don't planets have Circular orbits? This might be a completely wrong question, but this is bothering me since many days ago. Given the mass (Sun) curves the space around it, gravitation is the result of such curved space (Correct me if I am wrong, source: A Documentary film). Given any point on a circle with center same as center of the mass, curvature in the space should be equal (Intuition).   Planets rotate around the Sun because of the curve in the space they should follow a circular path and the distance between planet and Sun should be at a distance.  Given the fact that earth has a elliptical orbit around the sun, and the distance between Earth and Sun varies according to position of the earth. Why do we have a elliptical orbit not a circular orbit. In Age of Ultron, Thor seems to know something he possibly shouldn't? Sorry for the cryptic title, but I realise the film has only just been released in the UK and Europe and is yet to be released in the US.  I'll hide all substantial parts of my question, just in case. I don't want to spoil anything.     At the end of Age of Ultron, Thor states that 4 infinity stones have now shown up in the last few years.   So,     By my count we have the Tesseract, from several of the first few films. The Aether, from Thor 2. The Chitauri Scepter, again from several films. And finally, we have The Orb, from Guardians.    Now, to my knowledge     Thor, and indeed none of the Avengers, should know about The Orb. I don't remember Thor visiting the Collector between GoTG and the AoU. So, how did Thor know that The Orb had appeared? Or is he referencing a different infinity stone?   I'm looking for an in universe answer, ideally. Unable to modify files/folders in NTFS partition Convergence of $\sqrt{n}x_{n}$ where $x_{n+1} = \sin(x_{n})$ Consider the sequence defined as  $x_1 = 1$  $x_{n+1} = \sin x_n$  I think I was able to show that the sequence $\sqrt{n} x_{n}$ converges to $\sqrt{3}$ by a tedious elementary method which I wasn't too happy about.  (I think I did this by showing that $\sqrt{\frac{3}{n+1}} &lt; x_{n} &lt; \sqrt{\frac{3}{n}}$, don't remember exactly)  This looks like it should be a standard problem.   Does anyone know a simple (and preferably elementary) proof for the fact that the sequence $\sqrt{n}x_{n}$ converges to $\sqrt{3}$? I'm trying to install programs/files from the getdeb repo but get a "check your internet connection" error.  Programs than I've tried include Qbittorrent and Mozilla-Plugin-VLC.    Through the terminal I get the following errors:  Err http://archive.getdeb.net/ubuntu/ natty-getdeb/apps qbittorrent amd64 2.8.2-1~getdeb2   Could not connect to archive.getdeb.net:80 (209.105.191.78). - connect (113: No route to host) E: Failed to fetch http://archive.getdeb.net/ubuntu/pool/apps/q/qbittorrent/qbittorrent_2.8.2-1~getdeb2_amd64.deb: Could not connect to archive.getdeb.net:80 (209.105.191.78). - connect (113: No route to host)   &amp;  Err http://archive.getdeb.net/ubuntu/ natty-getdeb/apps mozilla-plugin-vlc amd64 1.1.10-1~getdeb1   Could not connect to archive.getdeb.net:80 (209.105.191.78). - connect (113: No route to host) E: Failed to fetch http://archive.getdeb.net/ubuntu/pool/apps/v/vlc/mozilla-plugin-vlc_1.1.10-1~getdeb1_amd64.deb: Could not connect to archive.getdeb.net:80 (209.105.191.78). - connect (113: No route to host)   I'm not having any problems adding/removing other programs/files from my machine.  Is there a problem with GETDEB repo (and if so, is there any way to fix it on my end) or is there something wrong with my computer's configuration? When ssh'ing, how can I set an environment variable on the server that changes from session to session? I just realized I can't unrar .rar files on my Ubuntu machine!  What's the easiest way to accomplish this fundamental task? If possible I'd love something like 7Zip that I can just right Click, and extract and have the program worry about how to do it regardless if it's a .zip, a .rar or a .foo compressed file. $\sum_{n=1}^\infty \log \frac{n+1}{n}$  $\sum_{n=1}^\infty \log \frac{n+1}{n}$ =  $\displaystyle\lim_{n \to{+}\infty}(\log2 - \log1)+(\log3-\log2)+...+(\log(n+1)-\log n)$=$\displaystyle\lim_{n \to{+}\infty}\log(n+1)\to \infty$. So, the series diverges.  Is my procedure correct? Here's a module with castellated pads attached to an eval board:  (source: ) Looking closely at the wires interfacing with the castellated pads, they're clearly soldered to the eval board. However, they don't look like they're soldered to the module, but rather they're being pressed against the pads with the tension in the wire. It also looks like the free end of the loops are protruding down into a channel cut in the PCB. Do these kind of connectors/metal loops have a name? Calculating square roots using the recurrence $x_{n+1} = \frac12 \left(x_n + \frac2{x_n}\right)$ Let $x_1 = 2$, and define $$x_{n+1} = \frac{1}{2} \left(x_n + \frac{2}{x_n}\right).$$ Show that $x_n^2$ is always greater than or equal to $2$, and then use this to prove that $x_n − x_{n+1} ≥ 0$. Conclude that $\lim x_n = \sqrt2$.   My question:  So I know how to do this problem but I don't know how to prove that $x_n &gt;0$ for all $n\in \mathbb{N}$. The origin of the value of speed of light in vacuum I have seen this question now many times and every question here and on other forum points to  experimental tutorial by . Now sadly a lot of answers are invalid right now because this central link is down. I couldn't find anything by Googling so if anybody has a fork of the tutorial or a second source that would be great? The link can't be gone for too long, I saw an answer with it 4 months ago.  The only other thing I have found is , but it also references the now missing tutorial. Any ideas how to find it? Find a function value given 2 points Given $f(x)$, which is differentiable at every point such that: $f'(x) \ge -5$ for every $ x \in R$   $f(2) = -13$, $f(9) = -48$  Prove that:$ f(3) = -18$  Now it's quite obvious that $ f(3) = -18$ since that if we know that the lowest value of the derivative is -5, the difference between $f(2)$ and $f(9)$ is $-48-(-13)=-35$  that means that that in the area $[2,9]$, $f'(x)=-5$ right? that's why I told that $f(3) = -18$, but I feel that my proof is insufficient, probably because I'm missing some theorems or such. can someone help me structure this proof into something RIGHT :)?  Thanks a lot! How can I take a photo with everything in focus with my DSLR? I am trying to write a VF page to list all the id and name columns from a custom object but found an error "List has more than 1 row" in the VF page.  Can anyone tell me what have I done wrong?  VF Page:  &lt;apex:page Controller="MP_controller" showHeader="false" sidebar="false"&gt;   &lt;apex:pageBlock&gt;      &lt;apex:pageBlockTable value="{! mp}" var="item"&gt;         &lt;apex:column value="{! item.id}"/&gt;         &lt;apex:column value="{! item.name}"/&gt;       &lt;/apex:pageBlockTable&gt;   &lt;/apex:pageBlock&gt; &lt;/apex:page&gt;   Apex controller  global with sharing class MP_controller {     public Merchant_Profile__c mp{get;set;}     public MP_controller(){         mp = [SELECT                  ID, name, Profile_account_name__c, Merchant_ID__c, Bank_Code__c, Country_Code__c,                 Currency_Code__c, Merchant_Level__c, Merchant_Type__c, MSO__c, Region__c,                 Retail_Products__c, Transaction_Mode__c, Created_Date__c, Date_Disabled__c, Date_Live__c,                 Merchant_Category_Code__c                FROM Merchant_Profile__c               WHERE Profile_Account_Name__c = '001O000000bQFnyIAG'];     } } Invalid Data Source when importing geojson to QGIS Im trying to import geojson, I add data, select protocol and use the uri  QGIS says "Invalid Data Source:  is not a valid or recognized data source"  I've followed the tutorial here  but I cant get the data to come in, any ideas? I'm using QGIS version 2.18.13