Figure 4
From: Spaceborne Synthetic Aperture Radar Survey of Subsidence in Hampton Roads, Virginia (USA)
Subsidence rate-map (left) and corresponding uncertainties (right) as estimated from historic (Sept 2007-Feb 2011) ALOS SAR data referenced to a GPS reference frame. Left, due to longer wavelength spatial variation (>20 km) of ionospheric InSAR noise, only InSAR subsidence rates within a 20 km radius of a GPS site (dashed circles) are use to locally reference InSAR to the vertical GPS rate. A weighed average is performed in the circle overlap regions to integrate the local referenced InSAR subsidence in a regional map. Right, propagated uncertainties shows the uncertainty grows with distance from a GPS station due to atmospheric noise, and areas falling within multiple circles to have a smaller uncertainty due to noise averaging. GPS-measured rates are shown in square and circular markers on the subsidence rate map, with the square markers representing the stations used for the GPS referencing and the circular markers stations used for comparison only. ArcGIS 10.4 software (http://www.esri.com/software/arcgis) was used to generate the figure. Service layer credits ESRI, HERE, DeLorme, MapmyIndia,© OpenStreetMap contributors and the GIS User community.
