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I wanted a straight-line distance. When I was calculating near distance on Arc GIS, I was only given the option between planar and geodesic distance.

But people in my field keep referring to my straight line distance as Euclidean.

I understand that planar is the default for my coordinate system (I think), and that it ignores surface curvature (which I wanted to ignore).

I am just worried that I calculated the wrong type of distance, but Euclidean was never an option in Arc GIS.

  • There is no wrong type of distance it just depends on the need. Do you want to build a tunnel or lay a cable? – GBG Jun 17 '16 at 15:54
  • Neither, sorry, I don't know what you mean. I wanted to clarify that the euclidean distance is not possible in a projected coordinate system. – Kelly Jun 18 '16 at 12:05
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First of all what is your coordinate system?

The people in your field are correct, the euclidean distance is the distance of a straight line between two points (also in 3 dimensions).

When your coordinate system is a projected one it is usually a planar surface, thats also correct. But it is not correct to say it ignores surface curvature. You need to take this into account, otherwise you would end up with large deviations already on smaller areas. The projection takes the shape of the geoid (the "earth-globe" ) and projects it into 2 dimensions. The curvature is "built in" your projection as 2-dimensional plane which is therefore distorted in some way (there are projections that keeps angles correct, shapes correct, areas correct, distances correct but never all at the same time).

This means: When you want to measure a direct line between two points it is correct to use the planar option in ArcGis.

  • Also in n-dimensions, the Euclidean distance is also used in multivariate space. – Jeffrey Evans Jun 17 '16 at 16:15
  • Yes, it's a projected coordinate system. Thanks for this, you explained everything very well, and I understand now. Thankfully, I can keep my distance measures. – Kelly Jun 17 '16 at 16:23

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