User Manual - pancroma

41. Working with Landsat GEOCOVER Data________________________________________________________________In August of 1998, NASA first produced positionally accurate GEOCOVERorthorectified Landsat imagery covering the majority of the Earth's land mass.The Landsat scenes used to create the GEOCOVER-Ortho products were handselected to provide the lowest cloud cover and highest quality data possible.GEOCOVER combined the best available horizontal and vertical control withdetailed manually measured tie points between adjacent imagery to create ahighly accurate spatial relationship between the raw Landsat imagery and thesurface of the Earth resulting in a positional accuracy of 50 meters root meansquare (RMS).The GEOCOVER 2000 worldwide set of satellite imagery from the Landsat 7Enhanced Thematic Mapper (ETM+) represents NASA’s latest effort. The ETM+30m multi-spectral bands 2, 4, and 7 were pan sharpened with the 15mpanchromatic band. These Landsat images were then ortho-rectified,georferenced, and projected in UTM WGS84.The GEOCOVER data set has several attractive features:• The images were selected to have exceptionally low cloud cover in mostcases• The orthorectification and georeferencing are of exceptionally high quality,making them very suitable for mapping work• The images are already pan sharpened to 15m resolution• Landsat band 2 (green) band 4 (near infrared) and band 7 (mediuminfrared) are less susceptible to atmospheric scattering than the visiblelight bands 1, 2 and 3 (blue, green, red) resulting in virtually haze-freeimages• The images are stretched so that their dynamic range fully spans the 256available digital number (DN) levels.One possible drawback for some applications is the image color. GEOCOVERimages display with unnatural vegetation, water and earth tones because of theselected bands as shown in the image below. Modifying these tones to makethem appear more natural preserves all of the benefits of GEOCOVER whilemitigating this drawback. PANCROMA TM has utilities for making such spectraltransformations.112