Alexander,<br><br>I didn't understand your requirements correctly I think PostGIS can help you with the aggregation with just a few SQL commands. If you want to do it programmatically, you have to loop through the layer's features and add up all the linestrings into a multilinestring according to your criteria.<br>
<br>FYI, The function GDALContourGenerate stores the contours as linestrings containing XYZ points. The elevation in stored in 'Z' whether or not it stored in a field.<br><br><div class="gmail_quote">On Thu, Apr 22, 2010 at 5:45 PM, Alexander Plum <span dir="ltr"><<a href="mailto:Alexander.Plum@cae.de">Alexander.Plum@cae.de</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">Hello there,<br>
<br>
I want to use the GDAL-function 'GDALContourGenerate' to construct highlines.<br>
<br>
Furthermore I make use of the OGRLayerH which should save the the vector-data-output (the result) of the function called above.<br>
<br>
I've read the OGR API Tutorial page (<a href="http://www.gdal.org/ogr/ogr_apitut.html" target="_blank">http://www.gdal.org/ogr/ogr_apitut.html</a>) und understood its content.<br>
But in my case the Layer shall save one vector with the different height values.<br>
For every height value there should exist one ring representing a highline. The rings should also be written into another vector.<br>
On top of that for every ring there has to be a vector (or let's say a matrix containing two vectors) with x- and y- values for certain positions of the ring.<br>
<br>
<br>
ring 1------ > x1 y1<br>
ring 2 x2 y2<br>
ring 3 ...<br>
... xN yN<br>
0,0 m -----------> ring N<br>
2,5 m<br>
5,0 m<br>
7,5 m<br>
10, m<br>
12,5 m<br>
...<br>
500,0 m<br>
<br>
<br>
So all in all I need three vectors saving the result of 'GDALContourGenerate'-function.<br>
<br>
My problem is that I do not know how to employ this OGRLayer. Please correct me, if this is a wrong way to use the'GDALContourGenerate'-function.<br>
<br>
Greetings,<br>
Alexander Plum<br>
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</font></blockquote></div><br><br clear="all"><br>-- <br>Best regards,<br>Chaitanya kumar CH.<br>/tʃaɪθənjə/ /kʊmɑr/ <br>+91-9848167848<br>17.2416N 80.1426E<br>