Ask A Cartographer

Extracting elevation values from a TIN to a polygon or raster

February 06 2008 | 6 comments
Categories: 3D Mapping, ArcGIS Methods, Map Data

I am having trouble figuring out how to extract averaged values from a TIN to a created polygon grid. I see that in Spatial Analyst i can extract values to points, but not polygons. I also have access to 3D Analyst if I need that.

Mapping Center Answer:

There are a couple of tools that can help here. First is the TIN to raster tool, and the second is the Interpolate shape tool. Both of these tools are in the 3D Analyst extension. The TIN to Raster tool will handle turning your TIN into a raster. Then either the TIN or the raster can be used as in put to the Interpolate shape tool. The results will be a bit different, so I would recommend trying both and choosing the result that best suits your purposes.

I'm not sure I interpretted the question fully, another possibility is that you want to use the TIN Polygon Tag tool, which is also in the 3D Analyst.

posted by Matt Burmeister on Feb 6 2008 11:34AM
I have tried using the Interpolate shape tool and it is not giving me the Z-values. It just creates a new polygon that has a reduced geometry (that is cut to the limits of the TIN.
posted by Charlie Frye on Feb 6 2008 11:43AM
Just to be clear, the Z-values are not stored as attributes, and the input feature class must be set up to have Z-Values. (When you create a new feature class in ArcCatalog, you have the option to check whether the geometry properties include M and/or Z values. If your's does not have Z values you can make a new feature class that has Z values, import the fields from the original, and use the Append tool to copy the data from the original feature class to the new feature class.)

Where the breaks occur is based on the TIN geometry or the raster cell size, which why I indicated trying both methods. Each has a use, and it depends on how you ultimately need to use this data as to which is better.
posted by Matt Burmeister on Feb 6 2008 11:47AM
When I use Interpolate Shape Tool the new feature that is created (tin2_InterpolateShape5) does not contain any new attribute information than did the original feature (Sample Grid_V3). I want the averaged elevation values from the TIN to be included in the new feature (tin2_InterpolateShape5).
posted by Charlie Frye on Feb 6 2008 11:55AM
Ah, so I would convert TIN to Raster, then the Raster to Points tool, then use the Identity tool to assign the FID of your polygons to the points. Then use the Dissolve tool to dissolve the points by polygon FIDs, using the field statistics to average the elevation values, and finally join the dissolved points via the polygon FID to the original polygons and if you want export the joined output and clean up the extra fields.
posted by Matt Burmeister on Feb 6 2008 12:41PM
Thanks Charlie! Exactly what I was looking for. BTW this service is awesome, keep it up!
Raster to tin posted by anthony doyle on Feb 23 2010 10:27AM
I want to convert a raster to tin but when i do so it comewp as a vertical bar,I think my peramiers are not right any advise woulsd be greatly appreciated

If you would like to post a comment, please login.

Contact Us | Legal | Privacy |