Le vendredi 31 janvier 2014 17:15:53, David Baker (Geoscience) a écrit : > 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?
No, it isn't currently, although I think it could be improved to have a in- memory index with moderate effort. But are you sure the slowness is due to the lack of index ? 55,000 is a big number, but not that big. Maybe the slowness just comes from the opening time (XML parsing) of such a big VRT. That would need to be profiled to be sure where the bottleneck is. > 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. > > Thanks, > David > > David M. Baker > Senior Advisor - Geoscience Technology > Chesapeake Energy Corporation > david.m.ba...@chk.com<mailto:david.m.ba...@chk.com> > > > ________________________________ > > This email (and attachments if any) is intended only for the use of the > individual or entity to which it is addressed, and may contain information > that is confidential or privileged and exempt from disclosure under > applicable law. If the reader of this email is not the intended recipient, > or the employee or agent responsible for delivering this message to the > intended recipient, you are hereby notified that any dissemination, > distribution or copying of this communication is strictly prohibited. If > you have received this communication in error, please notify the sender > immediately by return email and destroy all copies of the email (and > attachments if any). -- Geospatial professional services http://even.rouault.free.fr/services.html _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev