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<p class="MsoNormal"><span style="font-size:11.0pt; font-family:"Calibri","sans-serif"; color:#1F497D">Norman,</span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt; font-family:"Calibri","sans-serif"; color:#1F497D">Yes it does… At first I am looking to see if I can do this “off the shelf” with just the tools in the GDAL/ORG toolset. Are you thinking of using OGR to
do the spatial query with the spatialite db? Would a .qix indexed tile index shapefile work?</span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt; font-family:"Calibri","sans-serif"; color:#1F497D">David</span><span style="font-size:10.0pt; font-family:"Arial","sans-serif"; color:black">
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<p class="MsoNormal"><b><span style="font-size:10.0pt; font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt; font-family:"Tahoma","sans-serif""> Norman Vine [mailto:nhv@cape.com]
<br>
<b>Sent:</b> Saturday, February 01, 2014 8:23 AM<br>
<b>To:</b> David Baker (Geoscience)<br>
<b>Cc:</b> gdal-dev<br>
<b>Subject:</b> Re: [gdal-dev] Fast Pixel Access</span></p>
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<p class="MsoNormal">This is an application that is just screaming for a spatial index</p>
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<p class="MsoNormal">For starters you could build a spatialite db of the individual file extents</p>
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<p class="MsoNormal">that returned the filename to pass to gdallocationinfo</p>
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<p class="MsoNormal">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:</p>
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<p class="MsoNormal">Jukka,<br>
<br>
Jukka wrote:<br>
<br>
</p>
<p class="MsoNormal">I was experimenting with something like a "GIS service without a GIS server)<br>
and I have some examples online but...</p>
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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>
<br>
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Dev’s,<br>
<br>
I have a set of 55,501 bil files in a single directory. They are DEMS</p>
<p class="MsoNormal">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>
<br>
</p>
<p class="MsoNormal">of bil files, and have been able to access the elevation at a given</p>
<p class="MsoNormal">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>
<br>
</p>
<p class="MsoNormal">would first like to do this with the utilities before diving into code</p>
<p class="MsoNormal">(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>
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