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What is the best way to input CAD data into GIS to ensure greatest accuracy to known distances from scaled CAD site plans?

Question asked by ATSI_NickD on Nov 5, 2019

Geodesic vs. Planar continued... communicating with CAD data.

 

Hello! I work as an environmental consultant, and I frequently prepare maps in ArcGIS Pro Basic of scaled site plans overlaid aerial imagery. We get CAD data from surveyors and input that data into GIS to prepare said site plans. I have learned through trial and error a few different ways to georeference CAD data, including using the CAD to geodatabase tool and by using control points. 

 

My problem: I want to be sure that I am getting the most accurate measurements of known distances for small-scale projects (between 0-100 acres generally) on my maps. I have known values from CAD drawings that I use to create known-distance, planar edges on my parcel boundary polygons (I have done the same thing with geodesic edges, but the measurements were way off.)

 

I was instructed by the user before me to "always use geodesic measurement! NOT Planar." but after using the measure tool (and all of its variations i.e. Planar, Geodesic, Loxodromic, etc.) I am finding that for smaller sites, geodesic is not always "more accurate" which would make sense to me; when working with smaller sites (less than a half acre) it would make sense that there is less need to correct for the curve of the earth's surface. 

 

I'm open to any and all suggestions/guidance, thank you in advance!

  • What is the best way to input CAD data into GIS to ensure greatest accuracy to known distances from CAD scaled site plans?
  • What measuring tool and what parameters should I be using to measure my features?
  • If I create a feature with known distances, should I create them using planar or geodesic measurements?

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