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LeeDavis1
Frequent Contributor
since
07-04-2014
11-11-2020
44
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My Ideas
(6 Idea Submissions)Latest Contributions by LeeDavis1
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It is a unique problem. I am in the engineering business and these differences in length correlate to differences in material quantities, so we are talking about millions of dollars. Our data gets very detailed over long stretches of terrain. Thanks,
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12-20-2016
11:10 AM
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Good tool I have used that one. Notice how it returns LENGTH_GEO & LENGTH_3D as separate values. I am looking for a way to combine the effects of 3D and geodesic into a single length measurement. Could be possible to use this to get the % length added by geodesic and add that to the length 3d. Thanks
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12-20-2016
10:20 AM
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I have an interestingly similar problem. I need to calculate a route length very accurately which spans multiple UTM zones. I need to account for projection error, elevation, and curvature of the earth. I still have yet to find a way to calculate 3D geodesic length in one or two operations. I have done some initial experimentation on the effects of earth curvature on length and can tell you that the length adder is very small compared to the length added by elevation. For your particular problem I have a couple of recommendations. You are incurring alot of geometric error using South America Equidistant Conic, despite it being equidistant. Your distances and drive times will be way off. Here's what I would do: 1. Calculate a route ID number for all routes which you need to estimate. 2. Split up your road network by UTM zone (reproject each to the appropriate UTM zone; using only South zones is OK so you dont have to deal with another split at the equator). 3. Download SRTM 90m DEM for your entire project area. 4. Run Add Surface Information on each UTM zone road feature class using the 90m DEM. By doing this we can ignore geodesic length adder. Make sure to check on Slope Length. 5. Merge together the split up UTM zone feature classes back into one road network feature. Keep SlopeLength field and dont change it. 6. Run summary on Route ID and check on Sum for the SLength field. 7. Ta da, you have a table showing the accurate slope length of all your routes in one table. This can be joined back to your original single roads layer and you can calc the accurate length in that table for other use. Hope this helps. Lee
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12-20-2016
10:04 AM
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I have LIDAR coverage for a route which crosses multiple UTM zones. I want to calculate the length of this route as accurately as possible correcting for projection error, elevation, and curvature of the earth. I have figured out the first two parts but the curvature issue has stumped me. By modeling the Earth in AutoCAD using UTM WGS 84 parameters I've come up with a length multiplier of 1.000457002 to account for curvature but I'm not sure if that is correct, or if that can be multiplied with a 3D length to get the proper answer. All thoughts are appreciated. Thank you, -Lee
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12-20-2016
09:33 AM
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