<html><head><meta http-equiv="Content-Type" content="text/html charset=windows-1252"><meta http-equiv="Content-Type" content="text/html charset=windows-1252"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">This is an application that is just screaming for a spatial index<div><br></div><div>For starters you could build a spatialite db of the individual file extents</div><div>that returned the filename to pass to gdallocationinfo</div><div><br><div><div>On Feb 1, 2014, at 9:14 AM, "David Baker (Geoscience)" <<a href="mailto:david.m.baker@chk.com">david.m.baker@chk.com</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite">Jukka,<br><br>Jukka wrote:<br><blockquote type="cite">I was experimenting with something like a "GIS service without a GIS server)<br>and I have some examples online but...<br></blockquote><br>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.<br><br>David<br><br><br>-----Original Message-----<br>From: <a href="mailto:gdal-dev-bounces@lists.osgeo.org">gdal-dev-bounces@lists.osgeo.org</a> [mailto:gdal-<a href="mailto:dev-bounces@lists.osgeo.org">dev-bounces@lists.osgeo.org</a>] On Behalf Of Jukka Rahkonen<br>Sent: Saturday, February 01, 2014 7:09 AM<br>To: <a href="mailto:gdal-dev@lists.osgeo.org">gdal-dev@lists.osgeo.org</a><br>Subject: Re: [gdal-dev] Fast Pixel Access<br><br>David Baker (Geoscience <david.m.baker <at> <a href="http://chk.com">chk.com</a>> writes:<br><br><blockquote type="cite"><br><br><br>Dev’s,<br><br>I have a set of 55,501 bil files in a single directory. They are DEMS<br></blockquote>data that cover the US in 7.5 minute tiles. I would like to randomly access<br>elevations at a given lat/lon’s from the whole dataset. I created a vrt<br>file from the directory<br><blockquote type="cite"> of bil files, and have been able to access the elevation at a given<br></blockquote>lat/lon using gdallocationinfo, but because of the size of the dataset, this<br>operation is somewhat slow. Can the vrt be indexed? Or, is there a faster,<br>better way to access the pixels? I<br><blockquote type="cite"> would first like to do this with the utilities before diving into code<br></blockquote>(C#). The files are regularly named base on their location within a 1<br>arc-second grid.<br><br>I was experimenting with something like a "GIS service without a GIS server)<br>and I have some examples online but because of http connection the speed<br>comparison does not make sense.<br><br>Vrt combining biomass data from 13 single band tif files<br>gdallocationinfo<br>/vsicurl/<a href="http://latuviitta.kapsi.fi/data/metla/puuston_tilavuus.vrt">http://latuviitta.kapsi.fi/data/metla/puuston_tilavuus.vrt</a> -geoloc<br> 389559 6677412<br><br>DEM of Finland with 10x10 m grid through vrt<br>gdallocationinfo /vsicurl/<a href="http://latuviitta.kapsi.fi/data/dem10m/dem_10m.vrt">http://latuviitta.kapsi.fi/data/dem10m/dem_10m.vrt</a><br>-geoloc 389559 6677412<br><br>The same from a single BigTIFF<br>gdallocationinfo /vsicurl/<a href="http://latuviitta.kapsi.fi/data/dem10m/dem_10m.tif">http://latuviitta.kapsi.fi/data/dem10m/dem_10m.tif</a><br>-geoloc 389559 6677412<br><br>Feel free to download the originals if you want, they are all made from open<br>data. Just mention the National Land Survey of Finland, 2013 for the DEM and<br>Finnish Forest Reserch Institute, 2013 for the biomass data if you publish<br>data somewhere. The DEM datasets are about 10 GB each (Bigtiff + the<br>original small ones).<br><br>My tiffs have tiles but for this usage where only the value of a single<br>pixel is interesting striped tiffs could be as fast to read than tiled<br>tiffs. A trial would tell everything<br><br>-Jukka Rahkonen-<br><br><br>_______________________________________________<br>gdal-dev mailing list<br><a href="mailto:gdal-dev@lists.osgeo.org">gdal-dev@lists.osgeo.org</a><br><a href="http://lists.osgeo.org/mailman/listinfo/gdal-dev">http://lists.osgeo.org/mailman/listinfo/gdal-dev</a><br><br>________________________________<br><br>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).<br>_______________________________________________<br>gdal-dev mailing list<br>gdal-dev@lists.osgeo.org<br>http://lists.osgeo.org/mailman/listinfo/gdal-dev</blockquote></div><br></div></body></html>