Over the course of two years, from October 2015 to October 2017, over 2,000 Sentinel-1 images were used to create a map showing ground movement across the United Kingdom.
The map tracks areas of land subsidence and uplift based on processed data from Sentinel-1’s Synthetic Aperture Radar (SAR). SAR can be used to detect changes in surface heights with sub-millimeter precision in order to map land deformation.
How does Synthetic Aperture Radar (SAR) map land deformation?
Synthetic Aperture Radar (SAR) can be used to detect and measure land deformation by comparing SAR images of the same area acquired at different times. When there is deformation on the ground, such as subsidence or uplift, it can cause changes in the distance between the ground and the satellite, which in turn causes changes in the phase of the radar signal received by the satellite.
SAR can measure these changes in the ground either lifting up (uplift) or sinking (subsidence). Theses changes in the Earth’s surface are known as land deformation. The data is mapped as an interferogram.
An interferogram is a map that shows the changes in the phase of the radar signal over a particular area. These changes can be used to calculate the amount of ground deformation that has occurred.
Creating an interferogram to map land deformation
To create an interferogram, SAR images of the same area are acquired at two different times. The images are then processed to remove any noise in the radar signal that are not related to ground deformation, such as changes in the atmosphere or the satellite’s orbit. The two processed images are then combined to create an interferogram.
The interferogram shows areas where there has been ground deformation. The amount of deformation can be calculated by measuring the difference in phase between the two images.
By using multiple interferograms acquired over time, it is possible to create a time series of ground deformation measurements. This time series can be used to track the progress of deformation over time and to identify areas that are experiencing significant changes.
Land deformation map for the United Kingdom
The land deformation map was developed by Geomatic Ventures Limited, a commercial company spun off of the Nottingham Geospatial Institute, University of Nottingham. Known as the UK Relative Land Motion Map, it covers the United Kingdom with a spatial resolution of 90 meters.
The web map interface was built with Mango Maps.
Using a rainbow classification scheme, the map indicates ares that have subsided (trending red) or uplifted (trending blue) between 2015 and 2017. Users can search for areas by typing in a location or post code or use the pan and zoom tools.
There are also some areas outlined by rectangles that features areas of interesting subsidence or uplift.
- Visit: Sentinel-1 Relative Land Motion Map of the UK 2015-2017
- More: Map records UK’s small ups and downs, BBC News