Le jeudi 21 mai 2015 10:19:13, Yuta Sato a écrit : > Hi, > > I think the MOD021KM swath product is point data, which should be gridded > using the array of latitude and longitude given. > gdal griddata may be an option. However, it's very slow even for a single > band of MOD021KM product. > > MODIS team provides MODIS Swath Reprojection Tool for gridding the data, > which performs fast. > https://lpdaac.usgs.gov/tools/modis_reprojection_tool_swath > > I do not know the science behind MODIS Swath Reprojection Tool why it's > faster than the gdal griddata. > Can we discuss and implement a faster gridding tool in gdal? Why I am > focusing gdal is because the MODIS swath tool works only for MODIS data, > but the expected gdal tool would work for any data.
Yuta, Make sure your point layer has a spatial index before running gdal_grid on it. You will also need to specify reasonable values for the search radius. Even > > Thanks. > > On Thu, May 21, 2015 at 4:45 PM, Rutger <kass...@gmail.com> wrote: > > Hey, > > > > Maybe i'm missing something, but for as far as i know, the MODIS MOD021KM > > product is still a 'swath', and therefore still containing the bow-tie > > effect as the result of the scanning sensor. Wouldn't this mean that > > gdalwarp will never work? The lat/lon arrays aren't continuous, so any > > fitting (GCP/TPS) wont be accurate. And upsampling the arrays with cubic, > > like Even did, will result in interpolating pixels which are next each > > other > > in the array/file, but aren't next to each other 'on the ground', wont > > work well. > > > > I think you need to either use a dedicated algorithm (like gradient > > search), > > or something very generic (like the KDTree of Pyresample) to overcome the > > bow-tie effect. > > > > I have spend alot of time experimenting with this in GDAL, since i try to > > do > > as much with GDAL as possible. But projecting a swath file from a > > scanning sensor (like MODIS or VIIRS) is something i have never gotten > > to work. For some historic discussion about this see for example: > > > > http://osgeo-org.1560.x6.nabble.com/gdal-dev-reproject-python-numpy-binar > > y-swath-lat-lon-td4978609.html > > > > > > Regards, > > Rutger > > > > > > > > -- > > View this message in context: > > http://osgeo-org.1560.x6.nabble.com/gdal-dev-gdalwarp-problems-with-MODIS > > -L1B-tp5206583p5206825.html Sent from the GDAL - Dev mailing list archive > > at Nabble.com. > > _______________________________________________ > > gdal-dev mailing list > > gdal-dev@lists.osgeo.org > > http://lists.osgeo.org/mailman/listinfo/gdal-dev -- Spatialys - Geospatial professional services http://www.spatialys.com _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev