Glossary for Geospatial Science

Fourier transform: �A type of two-way frequency transform for identifying and removing unwanted spatial frequency components in an image.� The Fourier process is normally used to identify and remove systematic noise �spikes,� such as regular lines that may have been introduced by a faulty image collection device.� The process works as a two-way operation.� First the forward transform creates a pair of intermediate raster objects that reveal abnormal data variability.� After the values in those raster objects have been edited to remove the data spikes, the inverse transformation creates a raster object with the same image as the original, but with lines or other noise removed.� This Fourier Transform process has somewhat the same smoothing effect as the low-frequency TNTmips image filtering process.