Multisensor hydrologic assessment of a freshwater wetland

This article evaluates the use of synthetic aperture radar (SAR) and visibl e/infrared (VIR) satellite imagery for mapping the extent of standing water in the Peace-Athabasca Delta during spring and summer of 1998 SAR images c ontain data about the geometric and electrical characteristics of the objec ts, while VIR images contain information about the reflectivity of objects. Radar pulses can also penetrate vegetation to some degree depending on the wavelength and vegetation thickness. It is hypothesized that since Radarsa t and SPOT images contain complementary information, flood mapping will be more efficient when the true image types are used in combination. Radarsat SAR and SPOT multi-spectral imagery from May 1998 and July 1998 were used f or the flood mapping. A Radarsat S2 image (27.5 degrees incidence angle) wa s obtained for May 1998. To evaluate the incidence angle effect on flood ma pping, a Radarsat S1 image (27.5 degrees incidence angle) and a Radarsat S7 image (47.0 degrees incidence angle) were obtained for July 1998. The Rada rsat scenes were calibrated and filtered, and all imagery were orthorectifi ed to minimize geometric distortion. A Mahala-nobis distance algorithm was used to classify the SPOT scenes, the Radarsat scenes, and a combination of the two into open water flooded vegetation, and nonflooded land The result s indicate that flood mapping in both spring and summer conditions has sign ificantly higher accuracy when Radarsat and SPOT imagery are used in combin ation, rather than separately. However, it is important to use Radarsat ima gery acquired at low incidence angles. Classification of the SPOT scene com bined with the Radarsat S1 scene achieved significantly better results than those obtained when the SPOT scene was classified in combination with the Radarsat S7 scene. (C) Elsevier Science Inc., 2001. All Rights Reserved.