This is an application that is just screaming for a spatial index For starters you could build a spatialite db of the individual file extents that returned the filename to pass to gdallocationinfo
On Feb 1, 2014, at 9:14 AM, "David Baker (Geoscience)" <david.m.ba...@chk.com> wrote: > Jukka, > > Jukka wrote: >> I was experimenting with something like a "GIS service without a GIS server) >> and I have some examples online but... > > I am looking to do as you have, a RESTful service to query the elevation at a > given location. This will be used to in a DQM process as well as a geologic > application that needs the elevation of a proposed wellsite for data mining. > In both cases, 1000's if not tens of 1000's of calls will be made so > performance is an issue. > > David > > > -----Original Message----- > From: gdal-dev-boun...@lists.osgeo.org > [mailto:gdal-dev-boun...@lists.osgeo.org] On Behalf Of Jukka Rahkonen > Sent: Saturday, February 01, 2014 7:09 AM > To: gdal-dev@lists.osgeo.org > Subject: Re: [gdal-dev] Fast Pixel Access > > 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 > > ________________________________ > > 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). > _______________________________________________ > gdal-dev mailing list > gdal-dev@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/gdal-dev
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