Noura,<br>
<br>
First, note that osm tiles are presented in EPSG:900913 reference system.<br>
<br>
The usual way of requesting the tiles is based on the extent
coordinates. GDAL's WMS driver[1] can be used to access it. For that you
need an XML file[2] specifying the service.<br><br>Once you obtain the coordinates like Saâd explained, convert them to EPSG:900913 and use it obtain the tiles.<br>
<br>
[1]: <a href="http://www.gdal.org/frmt_wms.html">http://www.gdal.org/frmt_wms.html</a><br>
[2]: <a href="http://www.gdal.org/frmt_wms_openstreetmap_tms.xml">http://www.gdal.org/frmt_wms_openstreetmap_tms.xml</a><br><br><div class="gmail_quote">On Tue, Apr 10, 2012 at 2:17 PM, Saâd HESSANE <span dir="ltr"><<a href="mailto:saad.hessane@gmail.com">saad.hessane@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">DTED files are really simple to undertand. A DTED CD-ROM is organized like this :<br><ul><li><b>dted (folder)</b></li><ul>
<li><b>D### (folder)</b></li><ul><li>H##.dt# (file)<br></li><li>H##.dt# (file)<br></li><li>...<b><br>
</b></li></ul><li><b>D### (folder)</b></li><li><b>...<br></b></li></ul><li><b>gazette (folder)<br></b></li><li><b>text (folder)<br></b></li><li>dmed (file)<br></li></ul># : digit<br>D : The direction of the tiles E for East and W for West<br>
H : The hemispher of the tile : N for North and S for South<br><br><br>A DTED file represent data elevation of a square of 1°x1°. So the folder "e055" contain dted files that have longitude 55E. If the folder contain the file "n33.dt0", that mean the file contain data elevations of a 1°x1° square starting at 55E 33N (ending at 56E 34N).<br>
<br>Note about DTED specification :<br><ul><li>The DTED specification don't tell if the lettre have to be in capital lettre or not. So you can have "n33.dt0" or "N33.dt0". Be careful with that.</li>
<li>The specification don't tell to have contigu file or folder. So you can have a folder E055 and E060 without the folder between 55 and 60.</li></ul><p><br></p><p>I hope I answerd your question.<br></p><br><br><br>
<br>
<br><div class="gmail_quote">2012/4/10 len lee <span dir="ltr"><<a href="mailto:noura.salem.shamsi@gmail.com" target="_blank">noura.salem.shamsi@gmail.com</a>></span><br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div><div class="h5">
<div dir="ltr">hello;<br>
i downloaded dted data dt0 from raster roam website and there are 3
folders e055, e056 and e057 and within each folder there are 3 dted
files and i guess each dted file here represent a tile within my
terrain. now what am trying to do is requesting the terrain tiles
according to my dted data .. any idea how can i do that with gdal lib? <br>
i tried this:<br>
poDataset = (GDALDataset *) GDALOpen( "<a href="http://tile.openstreetmap.org/15/23687/15190.png" target="_blank">http://tile.openstreetmap.org/15/23687/15190.png</a>", GA_ReadOnly );<br>
<br>
to request a specific tile from openstreetmap server but as you can see i
need to know the exact coordinate system for that tile ... <br><br>please all what i need is to understand the process of requesting the tiles according to my dteds files;<br>
<br>
i will appreciate any help;<br>
thanks in advance; </div>
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