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I have a polygon of Idaho's borders in ArcMap. The southern border of the state is slightly curved. I realize that the Earth is curved in reality, but I want Idaho to look flat.

Is there a way to do this in ArcMap? I feel like a change in projection or coordinate system might help, but I don't know what those actually do, nor how to do it.

Any help is appreciated.

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Idaho's southern border lies along a so-called "line" of latitude. (Such "lines" are actually spherical circles centered at the poles.) Any cylindrical projection will render lines of latitude as straight segments on the map. – whuber Nov 26 '12 at 20:45
Just to clarify Kevin's point, if someone answers your question click the check mark under that answer's vote total. – HeyOverThere Nov 26 '12 at 21:45
up vote 6 down vote accepted

The attached image shows four coordinate systems. The top two are projected coordinate systems and the bottom two are geographic coordinate systems. I suspect you will like the visual appeal of the Idaho state system located in the top right dataframe. You can easily experiment with the look of various projections by assigning a projection to the dataframe using the following process:

  1. Right click the dataframe in the table of contents, select Properties > Coordinate System
  2. In the Coordinate System tab, choose any of the many projected or geographic coordinate systems
  3. To find the Idaho state system, select Projected Coordinate Systems > State Systems > NAD 1983 Idaho TM (Meters)

Keep in mind these changes are temporary and only apply to the dataframe properties. If you would like to make the projection permanent, use the Project (Data Management) tool

enter image description here

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It should be noted that when GIS software displays data in a "geographic" coordinate system", it is still projected in order to be displayed on your two-dimensional screen. It uses the equirectangular projection, which has degrees of longitude as the x and y axes. – dmahr Nov 26 '12 at 21:19

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