Hi all, I'm not sure if I'm doing something wrong or if I've found a bug in gdalwarp. I thought I'd ask here before putting in a trac ticket. Please let me know if this is the wrong procedure.
In any event, I have posted steps and links on gis.stackexchange that shows horizontal artifacts in the middle of images created during simple calls to gdal warp. Stack exchange link: http://gis.stackexchange.com/questions/116465/gdalwarp-leaves-horizontal-artifacts-regridding-from-ease-grid-laea-to-polarst Text of link follows: Hi there, I'm trying to understand how to use gdalwarp to warp an image. I believe I'm doing the basics correctly, but I might be missing some gdalwarp options? Any help would be greatly appreciate. The basic problem is that I see horizontal artifiacts in my output image. Here's the steps to reproduce. Start with a simple 722x722 image. http://imgur.com/UiMBqSd (you can save with http://imgur.com/UiMBqSd.png) apply metadata to make this a geotiff (this is a EASE-grid Lambert Azimuthal Equal Area projection on a 1924 authallic sphere.) gdal_translate -a_srs '+proj=laea +lat_0=90 +lon_0=0 +x_0=0 +y_0=0 +a=6371228 +b=6371228 +units=m +no_defs' \ -a_ullr -4524688.262500000 4524688.262500000 4524688.262500000 -4524688.262500000 \ -co COMPRESS=DEFLATE -co PREDICTOR=2 -co ZLEVEL=9 \ -of GTiff ./UiMbqSd.png ./UiMbqSd.withmetadata.tif This seems to have the expected geographic information (~12.5km grid) confirmed with gdalinfo gdalinfo UiMBqSd.withmetadata.tif Driver: GTiff/GeoTIFF Files: UiMbqSd.withmetadata.tif Size is 722, 722 Coordinate System is: PROJCS["unnamed", GEOGCS["unnamed ellipse", DATUM["unknown", SPHEROID["unnamed",6371228,0]], PRIMEM["Greenwich",0], UNIT["degree",0.0174532925199433]], PROJECTION["Lambert_Azimuthal_Equal_Area"], PARAMETER["latitude_of_center",90], PARAMETER["longitude_of_center",0], PARAMETER["false_easting",0], PARAMETER["false_northing",0], UNIT["metre",1, AUTHORITY["EPSG","9001"]]] Origin = (-4524688.262500000186265,4524688.262500000186265) Pixel Size = (12533.762500000000728,-12533.762500000000728) Metadata: AREA_OR_POINT=Area Image Structure Metadata: COMPRESSION=DEFLATE INTERLEAVE=PIXEL Corner Coordinates: Upper Left (-4524688.263, 4524688.263) (135d 0' 0.00"W, 29d42'45.71"N) Lower Left (-4524688.263,-4524688.263) ( 45d 0' 0.00"W, 29d42'45.71"N) Upper Right ( 4524688.263, 4524688.263) (135d 0' 0.00"E, 29d42'45.71"N) Lower Right ( 4524688.263,-4524688.263) ( 45d 0' 0.00"E, 29d42'45.71"N) Center ( 0.0000000, 0.0000000) (180d 0' 0.00"E, 90d 0' 0.00"N) Band 1 Block=722x2 Type=Byte, ColorInterp=Red Mask Flags: PER_DATASET ALPHA Band 2 Block=722x2 Type=Byte, ColorInterp=Green Mask Flags: PER_DATASET ALPHA Band 3 Block=722x2 Type=Byte, ColorInterp=Blue Mask Flags: PER_DATASET ALPHA Band 4 Block=722x2 Type=Byte, ColorInterp=Alpha If I then try to regrid it. gdalwarp -t_srs "+proj=stere +lat_0=90 +lon_0=-45 +lat_ts=70 +ellps=WGS84 +datum=WGS84 +units=m" ./UiMbqSd.withmetadata.tif ./regridded_lon0_-45.tif The problem I'm seeing is horizontal artifacts that appear to protrude horizontally around the middle of the image. You can see a png representation on imagur: http://imgur.com/Nrx4ZoS This occurs even with different lat_0 values. gdalwarp -t_srs "+proj=stere +lat_0=90 +lon_0=0 +lat_ts=70 +ellps=WGS84 +datum=WGS84 +units=m" ./UiMbqSd.withmetadata.tif ./regridded_lon0_0.tif Another png representation on imagur: http://imgur.com/uiiF9Ir I'm currently running this on a mac: > gdalwarp --version GDAL 1.11.1, released 2014/09/24 But I've tested and seen the same behavior on ubuntu 12.04: GDAL 1.10.1, released 2013/08/26 Any help solving this would be greatly appreciated. Thanks Matt -- Matthew Savoie - Senior Software Developer National Snow and Ice Data Center (303) 735-0785 http://nsidc.org _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
