Using ArcGIS Desktop, I want to calculate the nearest distance of points to lines, and I need distances to be in decimal degrees not meters.
How do I do this?
Even if I choose "decimal degrees" in the Near tool, the output seems to be in meters!
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What GIS software are you using?– PolyGeo ♦Commented Jul 5, 2018 at 19:58
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It is with ArcGis.– D_BCommented Jul 5, 2018 at 22:28
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Don't forget to take the Tour to learn about our focussed Q&A format. Please use the edit button beneath your question to provide any requested clarifications.– PolyGeo ♦Commented Jul 5, 2018 at 22:35
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2 Answers
Decimal degrees is problematic because the "distance" changes depending on where the data is. By setting decimal degrees, you're telling the software to treat the earth as an ellipsoid and distances are calculated using a geodesic-based method.
If you really want decimal degree distances, you'll need to strip off the coordinate system from the data so that it gets treated as "unknown coordinate system." If it's a shapefile, rename its .prj file. If it's a feature class, try using the Define Projection tool and 'clear' or set to none, the coordinate system. If that doesn't work, you may either need to convert it to a shapefile or create a feature class with no coordinate system (you'll have to change the xy domain, resolution, and precision values) and load/import the feature to the new feature class.
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From the documentation for the Near_analysis tool: "The distances calculated by this tool are in the unit of the coordinate system of the input features. If your input is in a geographic coordinate system and you want output distances to be measured in a linear unit (as opposed to decimal degrees), you must first project your input to a projected coordinate system using the Project tool. For best results, use an equidistant projection or a projection intended for your study area (UTM, for example)."– MattCommented Jul 6, 2018 at 22:48
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@Chris Depends on the version. Starting at 10.3, planar / geodesic options are available. (Make sure you're not looking at the coverage tool doc)– mkennedyCommented Jul 7, 2018 at 0:36
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I just needed to open File-new which gives a blank page with "unknown coordinate system". Then, without dragging layers to the table of contents, I used Near tool. The output is in decimal degrees. Thanks @mkennedy!– D_BCommented Jul 8, 2018 at 18:57
Seeing "meter" used as the measurement unit means your data is already projected. As a result, the returns are supposed to be meter-based for sure. When it comes to calculating the geometric attributes of features, ArcGIS works with projected surfaces rather than spherical surfaces.