<span style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">Hi all</span><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">
<br></div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">reviving this old thread because I'm interested in using the z-value (elevation) from kml files (type wkbMultiLineString25D) in a qgis plugin.</div>
<div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)"><br></div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">
Are there any plans to introduce z-value (25D) support in 2.0?</div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)"><br></div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">
Experimenting has shown that doing geom.exportToWkt() strips the z-value.</div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)"><br></div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">
How can I currently handle z-values? I understand that I would have to parse the wkb directly, is this possible in python? If so can someone give me some pointers?</div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">
<br></div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">Other option - external python library like shapely? It seems shapely does support z levels.</div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">
<br></div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">Or would it be simpler to parse the kml files by hand using an xml parser, as syntax is relatively simple?</div>
<div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)"><br></div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">
<br></div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">regards,</div><div style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)">
Etienne</div><br><div class="gmail_quote">On Mon, Dec 5, 2011 at 8:02 AM, Marco Hugentobler <span dir="ltr"><<a href="mailto:marco.hugentobler@sourcepole.ch" target="_blank">marco.hugentobler@sourcepole.ch</a>></span> wrote:<br>
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<pre>Hi Paul
Unfortunately, the current geometry system does not handle z- and
m-values in a sound way.
Some tools consider z and others don't. M-values are even more difficult
as they cannot be accessed by the QGIS API (z-coordinates can be read by
parsing the binary format of the geometry).
An overhaul of the geometry system is planned for version 2.
Regards,
Marco
On 05.12.2011 10:42, Paul Lens wrote:
> Hi all,
>
> 1. I made a TIN surface, using the interpolation plugin, from a point
> shapefile (with "ALTITUDE" field) and 3D line shapefiles. I lost time
> trying to extract the relevant lines from the line shapefiles without
> loosing the 3D information (Z values of the nodes).
> If I remember well, I first used "Merge Layers" from the mmqgis
> plugin, and it kept the Z information. Than, I used the Intersection
> command in the Vector menu, and the Z information was lost. Finally,
> after manually selecting the relevant lines and using "save as", I got
> the expected 3D line shapefile keeping the Z values.
> Is this loss of Z information a known limitation of the gdal vector
> commands in QGIS (vector menu) and is this limitation affecting all
> these commands? Or did I do something wrong?
>
> 2. In a second step, I wanted to be able to easily see (through
> labeling a Z field) or ask (with the identify command) those Z values
> from the 3D lines, so as to fine tune the interpretation of the
> topography.
> Again the gdal tool (in Vector menu) "Node Extraction" lost all Z
> information.
> Is there a workaround to create a point shapefile with a Z field? Or,
> at least, to keep the Z values in a point shapefile, rasterize it so
> as to be able to visualize the Z value using the "Identify" command
> on the raster?
>
> Thanking all the developers for this wonderful program,
>
--
Dr. Marco Hugentobler
Sourcepole - Linux& Open Source Solutions
Churerstrasse 22, CH-8808 Pfäffikon SZ, Switzerland
<span class="HOEnZb"><font color="#888888"><a href="mailto:marco.hugentobler@sourcepole.ch" target="_blank">marco.hugentobler@sourcepole.ch</a> <a href="http://www.sourcepole.ch" target="_blank">http://www.sourcepole.ch</a>
Technical Advisor QGIS Project Steering Committee
</font></span></pre>
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