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Cost-effective monitoring of land subsidence in developing countries using semipermanent GPS stations: a test study over Houston, Texas

Abstract. We present a cost-effective method for monitoring land subsidence in developing countries using measurements from semipermanent global positioning system (GPS) stations and interferometric synthetic aperture radar (InSAR) observations. The cost of maintaining a network of permanent GPS stations to monitor subsidence in developing countries might be implausible due to the high cost of maintenance. Hence, semipermanent GPS stations could be an alternative method, which densifies a GPS network with relatively inexpensive costs. We used three statistical methods to estimate the subsidence. We investigated the optimum time intervals for semipermanent GPS measurements based on the similarities of subsidence magnitudes and curve patterns with the permanent GPS measurements. In addition, we assessed the open source GPS processing tools based on the data quality of different session durations. Among the three models, the smoothing spline model showed the best estimation of subsidence. Among the different time interval data, 10- or 30-day time interval data were optimum for semipermanent GPS stations. Finally, we compared the GPS results to the InSAR-derived subsidence result, and both methods show that the northwestern Houston area subsides by about 1.5 to 2.0  cm/year. We anticipate that our method can be applied to other cities experiencing subsidence in developing countries.