The Landsat D Project will use, for the first time, a new sensor called the Thematic Mapper. This sensor is a mechanically scanned radiometer with seven spectral bands, which images the earth from space with a thirty meter spatial resolution. It will provide enhanced remote sensing capabilities relative to earlier Landsats, through improved spatial, spectral and radiometric resolution, global coverage and more rapid processing of data for users.
To meet high throughput rates and stringent accuracy requirements, new hardware architecture and novel algorithms for data processing are used. Image data is received on the ground at a 84.9 megabit/sec rate and is Processed to generate output images at 750,000 pixels per second or faster. Image processing on the ground proceeds in three steps. First, the sample intensities are radiometrically corrected. Next, the input sample positions are determined on a map grid. Finally, the output image is generated. The last step is called resampling.
The resampling procedure is analyzed in this paper, with particular emphasis on the effect that the sampling geometry has on the output image. Scan gaps and spacecraft jitter effects on the output image are studied by performing a simulation of the sampling and the resampling processes. The images produced under different scan geometries are displayed for visual assessment. Another means of comparing images to detect geometric distortion and radiometric error is developed. This is the difference image histogram, and it can be used to characterize the resampling errors. The results show that the resampling algorithm works excellently under all conditions. Distortion is visible only under extremely large scan gap conditions which rarely occur.
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