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Creating points from decimal degrees

February 22 2008 | 0 comments
Categories: ArcGIS Methods

I am having trouble creating points from latitude/longitude data in decimal degrees (i.e. 44.65743, -88.6746). When I use the add x/y data it looks like it need to be in linear units (feet in this case). I can't seem to remember or figure out how to do this. Please help!!

Mapping Center Answer:

When you add the XY data, you cannot (practically speaking) leave the Coordinate system set to unknown. At version 9.2 we made this a sort of 'in your face' problem because you'll see exactly what you're seeing, your lat/lon coordinates are now displayed relative to your data frame's coordinate system. In fact this is the case for all data with an unknown coordinate system. We used to have the concept of "Assumed Geographic", which meant if the coordinates were in a -90 to 90 and -180 to 180 box, we figured it was decimal degrees. The world of GIS has moved on and there are lots of site specific datasets without coordinate systems that got trapped by the Assumed Geographic logic, so we dropped it.

In your case make sure you know which geographic coordinate system your data is in. If you don't know try WGS84, and if that doesn't align well, try NAD83 (Assuming you're in North America).

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