<div dir="ltr"><div><div><div><div>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:<br><br>>> gdalwarp -s_srs EPSG:4326 -t_srs EPSG:3857 -r bilinear -of VRT merged.vrt srtm_merged_3857.vrt<br><br></div>and it processes fast (far far *too fast* for this global file) and returns<br><br></div>>> Creating output file that is 194835P X 479814L.<br></div>>> Processing input file merged.vrt<br></div>>> Using internal nodata values (eg. 0) for image merged.vrt<br><div><div><div><div><br></div><div>The return .vrt file definitely doesn't appear right...a quick look at the returned file:<br><br></div><div>input:<br><br>Size is 432000, 208800<br>Coordinate System is:<br>GEOGCS["WGS 84",<br>    DATUM["WGS_1984",<br>        SPHEROID["WGS 84",6378137,298.257223563,<br>            AUTHORITY["EPSG","7030"]],<br>        AUTHORITY["EPSG","6326"]],<br>    PRIMEM["Greenwich",0],<br>    UNIT["degree",0.0174532925199433],<br>    AUTHORITY["EPSG","4326"]]<br>Origin = (-180.000416666666670,84.000416666666666)<br>Pixel Size = (0.000833333333323,-0.000833333333323)<br>Corner Coordinates:<br>Upper Left  (-180.0004167,  84.0004167) (180d 0' 1.50"W, 84d 0' 1.50"N)<br>Lower Left  (-180.0004167, -89.9995833) (180d 0' 1.50"W, 89d59'58.50"S)<br>Upper Right ( 179.9995833,  84.0004167) (179d59'58.50"E, 84d 0' 1.50"N)<br>Lower Right ( 179.9995833, -89.9995833) (179d59'58.50"E, 89d59'58.50"S)<br>Center      (  -0.0004167,  -2.9995833) (  0d 0' 1.50"W,  2d59'58.50"S)<br>Band 1 Block=128x128 Type=Int16, ColorInterp=Gray<br>  NoData Value=0<br>  Overviews: 216000x104400, 108000x52200, 54000x26100, 27000x13050, 13500x6525,<br>6750x3263, 3375x1632, 1688x816, 844x408, 422x204<br></div><div><br>and output file:<br><br> 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                                 <br><br></div><div>One notably huge difference is that there is a huge jump in pixel size (from 0.000833333333323 to 205.686440189378940)...<br></div></div></div></div></div>