I have a line feature that, when using 'Calculate Geometry' in ArcGIS Pro, shows me it is approximately 7,000 US feet long.

I want to generate points every 10 feet on the line, and input that parameter to the 'Generate Points Along Line' tool as follows:

ArcGIS Pro Generate Points Along Line tool showing a parameter of 10 feet

This means I should expect about 700 points to be generated. However, I get a count of more like 680 points in the new layer that is created.

When I go to measure the points, reason becomes clear: it shows that the points are being measured every 12.06 ft. (sometimes 12.01, 12.11, etc.), instead of every 10 ft. (ignore the midpoint here): ArcGIS Pro measuring tool showing a line distance of 12.06 ft

What am I doing wrong here? I was guessing the coordinate system/projection (I'm just using a generic WGS 84 coordinate system on a WGS 84 Web Mercator Auxiliary Sphere basemap, the default for ArcGIS Pro), but being 2 feet off every 10 feet seems drastic, and the points are on the same coordinate system as the line.

Update: I've tested this on a fresh line I drew, and this is an issue with the Calculate Geometry tool not matching up with the Measure tool, not just with the Generate Points Along Line tool.

  • 1
    Web mercator is just about the worst projection for distance measurements. Use an equal-distance projection. See the Equidistant section in the Wikipedia article about Map Projections for some options. – csk Jul 25 '19 at 19:29
  • I fixed the issue after reprojecting the map and layers to a localized Projected Coordinate System and rerunning all tools, starting from Calculate Geometry, on that system--the measured distance between points was exactly 10.00 ft. after that. Thanks for your comment. – JMNC Jul 25 '19 at 21:12
  • Happy to help. If you post an answer to your own question it might help others who encounter the same issue. – csk Jul 26 '19 at 14:48

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