Speaker
Ms
Fiona Muirhead
(University of Edinburgh)
Description
High resolution (<1m, single look images), X-band airborne synthetic aperture radar (SAR) imagery was collected for sites of environmental interest in Scotland. The SAR system utilised was Selex ES’s novel, compact, low-cost airborne experimental platform. Its size, power consumption and lightweight build allow it to be placed on helicopters, fixed wing aircrafts and UAVs; making techniques such as SAR interferometry (InSAR) and coherent change detection (CCD) more widely available for civilian environmental applications. InSAR requires an extremely stable platform and is usually placed on a fixed wing aircraft, such as DLR’s E-SAR or a satellite, such as the new Tandem-X satellite, to overcome this issue. We show that InSAR can even be carried out from helicopter data, making the technique more accessible. The inertial measurement unit (IMU) is local to the radar allowing for the accurate motion compensation required to robustly carry out repeat pass InSAR. The use of airborne platforms, as opposed to satellites, for environmental monitoring allows for rapid deployment times to sites of interest and multiple viewing angles to help overcome issues caused by shadowing in final DEMs. A high resolution airborne system could complement a global coverage satellite system by analysing results from a smaller localised area.
The data was collected over a two day period in September 2014 for multiple sites of interest in Scotland with the system placed on a Twin Squirrel helicopter and overall 2000 spotlight SAR images were gathered. Up to seven repeat passes with differing flight paths were collected for some sites and multiple areas were imaged from different viewing angles. CCD results and digital elevation models (DEMs) for the sites collected can be used for many environmental applications. One example is for site management by the Royal Commission on the Ancient and Historical Monuments of Scotland (RCAHMS). The Scottish Environmental Protection Agency (SEPA) are interested in DEMs of sites for landslide and flood risk management. The data collection also covers sites for many more applications such as coastal erosion, forestry monitoring, subsidence detection and monitoring areas where mining activities take place.
Figure 1 shows Selex ES’s experimental SAR system placed on the Twin Squirrel helicopter. Figure 2 shows an example of an interferogram produced from two repeat pass images over a site with steep terrain. Figure 3 (a) and (b) show images of a field taken from two passes and (c) shows the CCD result between these two passes. It is clear that the field has been ploughed between revisits. This result shows the effectiveness of the small changes that can be detected using high resolution SAR images.
This research is a collaboration between Selex ES, the Schools of Geoscience and Engineering at the University of Edinburgh and the Knowledge Transfer Partnership (KTP).
Primary author
Ms
Fiona Muirhead
(University of Edinburgh)
Co-authors
Mr
Bernard Mulgrew
(University of Edinburgh)
Mr
David Greig
(Selex ES)
Mr
Gavin Halcrow
(Selex ES)
Mr
Iain. H. Woodhouse
(University of Edinburgh)
Mr
Samuel Ramsey
(Selex ES)
