I am experimenting with using 'gdalwarp' on a .vrt (first time), but I'm not sure what I'm doing wrong. I've been running this:
>> gdalwarp -s_srs EPSG:4326 -t_srs EPSG:3857 -r bilinear -of VRT merged.vrt srtm_merged_3857.vrt and it processes fast (far far *too fast* for this global file) and returns >> Creating output file that is 194835P X 479814L. >> Processing input file merged.vrt >> Using internal nodata values (eg. 0) for image merged.vrt The return .vrt file definitely doesn't appear right...a quick look at the returned file: input: Size is 432000, 208800 Coordinate System is: GEOGCS["WGS 84", DATUM["WGS_1984", SPHEROID["WGS 84",6378137,298.257223563, AUTHORITY["EPSG","7030"]], AUTHORITY["EPSG","6326"]], PRIMEM["Greenwich",0], UNIT["degree",0.0174532925199433], AUTHORITY["EPSG","4326"]] Origin = (-180.000416666666670,84.000416666666666) Pixel Size = (0.000833333333323,-0.000833333333323) Corner Coordinates: Upper Left (-180.0004167, 84.0004167) (180d 0' 1.50"W, 84d 0' 1.50"N) Lower Left (-180.0004167, -89.9995833) (180d 0' 1.50"W, 89d59'58.50"S) Upper Right ( 179.9995833, 84.0004167) (179d59'58.50"E, 84d 0' 1.50"N) Lower Right ( 179.9995833, -89.9995833) (179d59'58.50"E, 89d59'58.50"S) Center ( -0.0004167, -2.9995833) ( 0d 0' 1.50"W, 2d59'58.50"S) Band 1 Block=128x128 Type=Int16, ColorInterp=Gray NoData Value=0 Overviews: 216000x104400, 108000x52200, 54000x26100, 27000x13050, 13500x6525, 6750x3263, 3375x1632, 1688x816, 844x408, 422x204 and output file: Size is 193861, 479814 Coordinate System is: PROJCS["WGS 84 / Pseudo-Mercator", GEOGCS["WGS 84", DATUM["WGS_1984", SPHEROID["WGS 84",6378137,298.257223563, AUTHORITY["EPSG","7030"]], AUTHORITY["EPSG","6326"]], PRIMEM["Greenwich",0, AUTHORITY["EPSG","8901"]], UNIT["degree",0.0174532925199433, AUTHORITY["EPSG","9122"]], AUTHORITY["EPSG","4326"]], PROJECTION["Mercator_1SP"], PARAMETER["central_meridian",0], PARAMETER["scale_factor",1], PARAMETER["false_easting",0], PARAMETER["false_northing",0], UNIT["metre",1, AUTHORITY["EPSG","9001"]], AXIS["X",EAST], AXIS["Y",NORTH], EXTENSION["PROJ4","+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"], AUTHORITY["EPSG","3857"]] Origin = (-19837179.642485119000000,18807657.848855246000000) Pixel Size = (205.686440189378940,-205.686440189378940) Corner Coordinates: Upper Left (-19837179.642,18807657.849) (178d12' 1.50"W, 84d 0' 1.50"N) Lower Left (-19837179.642,-79883575.764) (178d12' 1.50"W, 89d59'58.50"S) Upper Right (20037399.339,18807657.849) (179d59'56.47"E, 84d 0' 1.50"N) Lower Right (20037399.339,-79883575.764) (179d59'56.47"E, 89d59'58.50"S) Center ( 100109.848,-30537958.958) ( 0d53'57.49"E, 89d 2'43.78"S) Band 1 Block=512x128 Type=Int16, ColorInterp=Gray Overviews: 96931x239907, 48466x119954, 24233x59977, 12117x29989, 6059x14995, 3030x7498, 1515x3749, 758x1875, 379x938, 191x471 One notably huge difference is that there is a huge jump in pixel size (from 0.000833333333323 to 205.686440189378940)...
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