Comparison and integration of spaceborne optical and radar data for mapping in Sudan

Abstract

The purpose of this study was to determine how different procedures and data, such as multiple wavelengths of radar imagery and radar texture measures, independently and in combination with optical imagery influence land-cover/use classification accuracies for a study site in Sudan. Radarsat-2 C-band and phased array L-band synthetic aperture radar (PALSAR) L-band quad-polarized radar were registered with ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) optical data. Spectral signatures were obtained for multiple landscape features, classified using a maximum-likelihood decision rule, and thematic accuracies were obtained using separate validation data. There were surprising differences between the thematic accuracies of the two radar data sets, with Radarsat-2 only having a 51% accuracy and PALSAR 73%. In contrast, the optical ASTER overall accuracy was 81%. Combining the original radar and a variance texture measure increased the Radarsat-2 to 78% and PALSAR to 80%, whereas the two original radar bands together had an accuracy of 87%. Sensor fusion of optical and radar obtained an accuracy of 93%. Based on these results, the use of multiwavelength quad-polarized radar imagery combined or integrated with optical imagery has great potential in improving the accuracy of land-cover/use classifications. In tropical and high-latitude regions of the world, where persistent cloud cover hinders the use of optical satellite systems, land management programmes may find this research promising.

Additional information

Funding

The authors would like to thank the following organizations for providing and/or funding the imagery used and for supporting this research. Radarsat-2 images were provided by the Canadian Space Agency under project3126 of the Science and Operational Application Research for Radarsat-2 program. The Alaska Space Facility, under sponsorship from NASA, provided the PALSAR imagery. The NASA Land Processes Distributed Active Archive Center at the USGS/Earth Resources Observation and Science (EROS) Center provided the ASTER imagery. Finally, additional support was provided through grants received from the Department of Geography and Geoinformation Science at George Mason University.