Thematic Mapper Image Quality: Registration, Noise, And Resolution

Abstract

This paper provides an assessment of Thematic Mapper data quality in terms of band-to-band registration, periodic noise, and spatial resolution. Based on the Thematic Mapper images analyzed so far, the band-to-band registration accuracy is very good. For bands within the same focal plane, the mean misregistrations are well within the specification, 0.2 pixel, except for the thermal band. The thermal band was misregistered by three pixels in each direction in early data products. The error in the across-scan direction was close to zero in later data products. For bands between the cooled and uncooled focal planes, there was a consistent mean misregistration of 0.5 pixels along-scan and 0.2-0.3 pixels across-scan, larger than the specified 0.3 pixel error for bands between focal planes. An analysis of the standard deviation of the misregistration indicated all band combinations would meet the registration specifications if the mean misregistrations were removed by the data processing software. Analysis of the periodic noise in one image indicated a noise component in bands 1-4 with a spatial frequency of 0.31 cycles/pixel. Other lower amplitude periodic components were also present. The periodic noise components obscured detail in areas of low contrast. Modulation transfer function (MTF) analysis in a comparative mode showed no difference in MTF between the forward and backward scans. The difference in MTF between radiometrically corrected data and geometrically corrrected data appeared to be attributable largely to the cubic convolution resampling used to derive the geometrically corrected data.