evenr
what about the use of a tileindex? seems an intersection with a set of polys first would be quick brian On Fri, 2014-01-31 at 19:30 +0100, Even Rouault wrote: > 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 _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev