In which unit is the nearest distance calculated with Near tool?

VincentLaunstorfer

Hi,

I used the Analysis -> Proximity -> Near tool to calculate the nearest distance between:

- a Point feature class as Input

- a Line feature class as Near

Whatever the GCS of the Input feature class (Geographic NAD27, Projected NAD27 Albers Equal Area Conic), or the GCS of the .mxd project, the reslt is always the same. And it looks as being Meters if I double-check with the  Measure tool.

The only diffrence I can output is if I use Geodesic or Planar option, which shows a little difference... (and looks logic).

My question is what is the unit of the calculated nearest distance? Looks like to be Meters, but why is it that by default?

And how is it possible to set another unit for nearest distance?

Thanks

DanPatterson_Retired

A GCS is a geographic coordinate system aka the units are in decimal degrees.  A PCS is a projected data set and for most of the world, the projection used will transform space so that position (and hence distance) are recorded in meters.  undoubtedly you have a projected coordinate system.  The method of calculating distance using geodesics will result in measures being made in meters having performed the calculation using decimal degree locations, determining the 'great circle' distance (if you like), then converting the distance measure to human readable form ... meters.  A planar distance determined from projected coordinates using Euclidean distance calculations.  The results of geodesic vs planar will be very similar for locations close together.  The differences 'may' get larger depending on the projection used, where you are on Earth and how far apart the locations are.  

In short, if you are working 'locally' versus 'globally'... use projected data.  If you really need the distance along the geodesic, then use it...