id,summary,reporter,owner,description,type,status,priority,milestone,component,version,severity,resolution,keywords,cc 5714,Bilinear Interpolation Incorrect,johanstenberg,warmerdam,"Hi, My name is Johan Stenberg and I work as a software consultant for GeoTrellis. When looking for a reference implementation of bilinear interpolation, I looked at GDAL's bilinear interpolation and I think it's broken. I have here attached a file for which the command : ""gdalwarp -r bilinear -s_srs '+proj=longlat +datum=WGS84 +no_defs' -t_srs '+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs' nlcd_tile_wsg84.tif nlcd_tile_webmercator-bilinear.tif"" Generates a bad file. It's bad because in the resulting file (there might be more errors than this one) one value is -31488.0. There is no value in the original file that is lower than -30000, so that should not be able to happen in regular bilinear interpolation. I've been trying to spot the error myself but I haven't had any success. Thanks, Johan",defect,closed,normal,,Algorithms,svn-trunk,major,invalid,bilinear,