Correcting geo-location interpolation errors in NESDIS-produced AVHRR 1b data near the Poles
Researchers using AVHRR level 1b data produced by NESDIS Operations interpolate most geo-located pixels. Each scanline has count values for either 409 GAC or 2048 LAC pixels, but geo-locations at only 51 anchor pixels. Quadratic interpolation separately in longitude and latitude is commonly used to estimate the missing geo-locations. This is accurate, except for latitudes poleward of 86° N or 86° S. Interpolation errors can be 15 km near the poles, compared with 0.3 km at 40° N. Rapidly converging lines of longitude near the poles cause the problem. The Gnomonic map projection is an accurate representation of the Earth near a pole. The strategy - (1) convert the anchor pixel coordinates from (long, lat) to Gnomonic, (2) interpolate in the Gnomonic coordinates, and (3) convert the interpolated locations back to (long,lat) coordinates - reduces interpolation errors to 0.5 km, even near the poles.
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Document Type: Research Article
Publication date: 2007-01-01