David Baker (Geoscience <david.m.baker <at> chk.com> writes: > > > > Dev’s, > > I have a set of 55,501 bil files in a single directory. They are DEMS data that cover the US in 7.5 minute tiles. I would like to randomly access elevations at a given lat/lon’s from the whole dataset. I created a vrt file from the directory > of bil files, and have been able to access the elevation at a given lat/lon using gdallocationinfo, but because of the size of the dataset, this operation is somewhat slow. Can the vrt be indexed? Or, is there a faster, better way to access the pixels? I > would first like to do this with the utilities before diving into code (C#). The files are regularly named base on their location within a 1 arc-second grid.
I was experimenting with something like a "GIS service without a GIS server) and I have some examples online but because of http connection the speed comparison does not make sense. Vrt combining biomass data from 13 single band tif files gdallocationinfo /vsicurl/http://latuviitta.kapsi.fi/data/metla/puuston_tilavuus.vrt -geoloc 389559 6677412 DEM of Finland with 10x10 m grid through vrt gdallocationinfo /vsicurl/http://latuviitta.kapsi.fi/data/dem10m/dem_10m.vrt -geoloc 389559 6677412 The same from a single BigTIFF gdallocationinfo /vsicurl/http://latuviitta.kapsi.fi/data/dem10m/dem_10m.tif -geoloc 389559 6677412 Feel free to download the originals if you want, they are all made from open data. Just mention the National Land Survey of Finland, 2013 for the DEM and Finnish Forest Reserch Institute, 2013 for the biomass data if you publish data somewhere. The DEM datasets are about 10 GB each (Bigtiff + the original small ones). My tiffs have tiles but for this usage where only the value of a single pixel is interesting striped tiffs could be as fast to read than tiled tiffs. A trial would tell everything -Jukka Rahkonen- _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev