~~META:
creator = Christian Heine
&date created = 2012-03-30 
~~

====== OGR2OGR in the 3rd dimension ======

I had to convert shapefile data from 2D lines/points to files consisting of 3 fields (x,y,z) for further processing using the [[http://www.soest.hawaii.edu/gmt5/|GMT5]]. I was about to write some Python code to do that myself when I realised a new (GDAL >1.8) option in the [[http://www.gdal.org/ogr2ogr.html|ogr2ogr tool]]:

<code>
   -zvalue Uses the specified field to fill the Z coordinate of geometries.
</code>

Turning an attribute from a shapefile into a z-Value for GMT files ogr2ogr and this flag is easy and helps to avoid ArcGIS’ 3D Analyst’s “Feature Attribute to Z-Value” function.

Simple usage:

<code bash>
ogr2ogr -F"GMT" OutFileWithZValues.gmt InFileWithZAttribute.shp -zfield"Thickness"
</code>

Done. Even works the other way around: from an OGR GMT file with Z-values in the 3rd column to a 2.5D shapefile:

<code bash>
ogr2ogr -F"ESRI Shapefile" OutFileWithZAttribute.shp InFileWithZValues.gmt -nlt LINESTRING25D
</code>

~~DISCUSSION~~