NEAR Analysis tool help

Question

I am currently working on the Understanding GIS An ARCGIS project workbook, I am in lesson 6 Exercise 6c , Step 10 letters d-g, I am trying to use the near analysis tool to get the distance from the input feature to the nearest feature, I keep on getting -1 as values, meaning it is not reading anything around me.

any suggestions as to why this is not working, i tried specifiying a radius but still nothing works

GayathriAlallasundaram · Answer

I am currently working on the Understanding GIS An ARCGIS project workbook, I am in lesson 6 Exercise 6c , Step 10 letters d-g, I am trying to use the near analysis tool to get the distance from the input feature to the nearest feature, I keep on getting -1 as values, meaning it is not reading anything around me.

any suggestions as to why this is not working, i tried specifiying a radius but still nothing works

Hi,

The document for Near Analysis tool states that "The values for NEAR_FID and NEAR_DIST will be -1 if no feature is found within the search radius." So check if the radius specified is correct, also make sure the data is in projected coordinate system and not in geographic coordinate system.

Regards,
Gayu

ChrisNoll · Answer

Hi VintageH2, Since your description was rather vague, I can only suggest you check that both inputs are using the same coordinate system and proejction.

I encountered a similar problem with the Near Analysis tool. After converting a raster to points to use as input features, I was trying to get the distance of land cover points to my near feature, a lake shapefile.  Both inputs were in the same projection and coordinate system.

Something did not calculate correctly using the default paramaters, and a curious pattern resulted where all of the "-1" values, which indicates that no match was found in the search radius, were consistently found on the upper half of the area of interest.

Once I gave it a proper search radius, the problem went away. It was strange since the tool help indicates that the search radius is optional, and "all near features are considered for calculation" if no radius is specified.  Seems like a bug to me, or maybe just poor tool help documentation.

(Using Service Pack 3, and ArcPy to batch process.)