Topographic Corrections of Satellite Data for Regional Monitoring

• Published in: Photogrammetric engineering and remote sensing 2012-09, Vol.78 (9), p.973-981
• Main Author: Goslee, Sarah C.
• Format: Article
• Language: English
• Subjects: Animal, plant and microbial ecology; Applied geophysics; Biological and medical sciences; Earth sciences; Earth, ocean, space; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; General aspects. Techniques; Illumination; Internal geophysics; Monitoring; Reflectance; Reflectivity; Regional; Teledetection and vegetation maps; Topography; Vegetation
• ISSN: 0099-1112; 2374-8079
• DOI: 10.14358/PERS.78.9.973

The increased availability of satellite imagery has made regional monitoring programs possible. To compare images taken at different times, variation in reflectance caused by the interaction of sun position and topography must be corrected. Previous studies of topographic correction methods have often used only single scenes taken under good conditions, and even then have found mixed effects. Six correction methods were tested on two Landsat scenes (TM and ETM +) in central Pennsylvania obtained at low, medium, and high solar elevations. The effects of the corrections on band reflectance values and two ratio-based vegetation indices were assessed. Lambertian methods should not be used for regional monitoring of vegetation: these corrections are not band-specific, and thus do not remove topographic effects on vegetation indices. Instead, non-Lambertian methods such as the c-correction or Minnaert methods, particularly cover-based modifications of the latter, should be used. No methods provide effective correction under conditions of low or negative illumination, though such conditions are often found. An integrated approach including atmospheric corrections may offer a way to reduce topographic effects even at low illumination.