Digital Terrain Elevation Data (DTED) Anomaly Removal through the Use of an Interactive Fourier Frequency Filtering Process.

Abstract

Abstract : The Defense Mapping Agency is a producer of raster formatted elevation data in a form called DTED (Digital Terrain Elevation Data). This data is collected from digitized source maps and from optically or digitally correlated stereopairs of photographic imagery. The various means used in producing DTED sometimes introduce a striation anomaly into the data. Conventional techniques for handling this anomaly have included the use of convolution with smoothing filters. Smoothing, however, degrades the high quality resolution of the data. A more precise method specific only to the anomaly was required. To accomplish this, an interactive Fourier frequency filtering program was designed to allow analysis and filtering of the DTED in the frequency domain. The process allows the analyst to use the data's amplitude spectrum as an aid in designing an area specific low-pass, band-reject, or fan- reject filter. This technique can result in almost total elimination of the striation anomaly with virtually no degradation of the high quality resolution of the data. (Author)