Thanks Even, I managed to make them aligned (illustration: https://i.imgur.com/1TwmVMN.png) from your valuable suggestion with these 2 commands (-tr are used same for both gdapwarp and -tap option is the critical):
gdalwarp -tr 0.0007161230037719291 -0.0007161230037719291 T32UQD_20200421T102021_TCI_60m.jp2 full_warp.tif -t_srs EPSG:4326 -dstnodata 0 -tap gdalwarp -tr 0.0007161230037719291 -0.0007161230037719291 crop.tif small_warp.tif -t_srs EPSG:4326 -dstnodata 0 -tap On Tue, 12 May 2020 at 18:12, Even Rouault <[email protected]> wrote: > On mardi 12 mai 2020 16:19:43 CEST Pham Huu Bang wrote: > > > Hello, > > > > > > I've a Sentinel 2 UTM32 scene (JPEG2000 format). > > > > > > What I want to do is: > > > > > > + Warp this scene from UTM32 to EPSG:4326 by gdalwarp > > > gdalwarp T32UQD_20200421T102021_TCI_60m.jp2 -t_srs EPSG:4326 > full_warp.tif > > > > > > + Clip a small subset of this file by gdal_translate > > > gdal_translate -projwin 798326.68347 5795956.80269 799609.577326 > > > 5794397.95642 T32UQD_20200421T102021_TCI_60m.jp2 crop.tif > > > > > > Then warp this small subset also from UTM32 to EPSG:4326 by gdalwarp: > > > > > > gdalwarp crop.tif -t_srs EPSG:4326 small_warp.tif -dstnodata 0 > > > > > > However, when I overlay the small_warp.tif on the full_warp.tif by > > > QGIS 2.14.9, I see the small file is not aligned on the big one. > > > > > > Illustration: https://i.stack.imgur.com/U5Vql.png > > > > > > What can be the reason for it? > > > > When you don't specify any target extent or resolution, gdalwarp guesses > them from the input raster georeferencing and target SRS. It doesn't try to > align on any particular resolution > > > > You may want to use the -tr and -tap switches to specify a target > resolution, and constraint the extents to be aligned on it. > > > > Another reason for the misalignment is that you use the default nearest > resampling. Using -r cubic could likely improve things > > > > To get perfectly overlapping images, you may also need to specify -et 0 > > > > Even > > > > -- > > Spatialys - Geospatial professional services > > http://www.spatialys.com > -- *Bang Pham Huu * *-------------------------------------------------------------------------------------* *Master of Science - Research Assistant at Field Monitoring Center - 4 F, E3 BuildingViet Nam - Ha Noi National University - University of Engineering and Technology* *Email: [email protected] <[email protected]> - Tel: +84 164.6339.217* *“Life is like riding a bicycle. To keep your balance, you must keep moving.”― Albert Einstein*
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