topic Re: Determining elevation values for contours based on limited annotation/point values in Geoprocessing Questions

Determining elevation values for contours based on limited annotation/point values

Mattborski — Tue, 28 Sep 2021 17:46:22 GMT

I've seen this touched on in a few other posts but no real solution.

I have a contours feature class with elevation values for only about 500 of the 5,000 contours and need to determine the elevation for the remaining contours. I also have an annotation layer showing elevation that I converted to a point feature (so about 1600 points with an elevation value).

I don't think the Near tool alone would be beneficial hear because of how much the elevation is changing over just a couple meters. If I were to run the Near tool without a distance limiter, the nearest elevation point to a contour could be several meters away and the interpolated elevation would be way off. I have run it with a distance limiter of one meter to get estimated values for another 600 or so contours. Not sure how to get elevation values for the remaining contours.

Would topo to raster be beneficial here? Meaning, run it based on the points or contours I have values for now, and then interpolate the remaining contour elevation values off of the generated raster?

Re: Determining elevation values for contours based on limited annotation/point values

JayantaPoddar — Tue, 28 Sep 2021 20:10:47 GMT

Topo to Raster would definitely be the go-to tool. You could simultaneously add both contours and point elevations as inputs.

How Topo to Raster works

If your ultimate aim is to generate contour lines, use Contour (3D Analyst)—ArcGIS Pro | Documentation to the surface raster generated in the above step.

Re: Determining elevation values for contours based on limited annotation/point values

Mattborski — Tue, 28 Sep 2021 22:25:14 GMT

Thanks! Appreciate the response. Continuing to run different variations of this workflow and will report back on how it worked out. I created new contours from the raster I created from the original contours. Then I used the Near tool and a join to have the elevation values from the generated contours to be added to the contours from the original data (hope that made sense).

Re: Determining elevation values for contours based on limited annotation/point values

Anonymous User — Wed, 29 Sep 2021 00:18:34 GMT

Hi Matt:

Do you have trustworthy existing raster elevation data for your study area? If so, could you use the InterpolateShape tool to "drape" your contour features onto that known surface?

'Interpolate' in this case refers to the fact that the input polylines would be densified and elevation samples from the raster assigned as z values to those additional vertices.

This tool is also available with a spatial analyst license.

-Jim TenBrink

spatial analyst team

Re: Determining elevation values for contours based on limited annotation/point values

Mattborski — Thu, 30 Sep 2021 20:54:50 GMT

Thanks, Jim. I wasn't aware of that tool. I ran it but don't see a field with the z/elevation values populated in the new feature class. Is that just stored in the geometry?

Re: Determining elevation values for contours based on limited annotation/point values

Anonymous User — Thu, 30 Sep 2021 22:34:34 GMT

Correct, the z values are stored in the individual vertices of the output PolylineZ feature geometries.

The related tool Add Surface Information might be more useful to you. It will report as separate output fields the min, max and average z encountered by each entire input geometry . Its also available with either a 3d or spatial analyst license.

-jt

Re: Determining elevation values for contours based on limited annotation/point values

Mattborski — Fri, 01 Oct 2021 15:33:33 GMT

Great. Thanks, Jim. Ran this one. This tool may prove to be the most useful for what I'm trying to do. Appreciate the help!