topic Re: Spatial Intopolation using 12 points in ArcGIS Spatial Analyst Questions

Spatial Intopolation using 12 points

luckyphil78 — Sun, 06 Oct 2013 02:28:08 GMT

Im a novice user.

Im trying to perform spline and IDW interpolations from 12 points to produce an elevation model of groundwater levels, but ArcGIS spits back an error and says that I don't have enough points.

What is the minimum amount of sample points needed for spatial analysis interpolation?

Is there a way I can produce a set of DEM's from 12 sample points?

Re: Spatial Intopolation using 12 points

XanderBakker — Tue, 08 Oct 2013 12:50:24 GMT

Hi Philip,

Performing an IDW on 12 sample points is not very much. As the Help (IDW Spatial Analyst) states:
The best results from IDW are obtained when sampling is sufficiently dense with regard to the local variation you are attempting to simulate.

There is no limit in the minimum number of point. There is a limit when it comes to the maximum number of points:
This tool has a limit of approximately 45 million input points.

See also the Help topic How IDW works

I just did a test with default settings on 12 random points and it worked (using 10.2). See screen shot:

[ATTACH=CONFIG]28120[/ATTACH]

Can you indicate the settings you're using and/or can you attach the dataset you're using? That makes it easier to determine the cause.

Kind regards,

Xander Bakker

Re: Spatial Intopolation using 12 points

luckyphil78 — Wed, 09 Oct 2013 05:22:32 GMT

Thanks Xander,

Ive tried changing the parameter's in the tool to see if it works, but cant get any results.

I get 2 errors in the results window:-
Error 010098: Insufficient number of points.
Error 010067: Error in executing grid expression.

The location of my points are irregular, but I don't think that would be a hindrance. Ive checked the field details in my tables and all the data types are in Double. My table contains not only X, Y and Z data (Z being the water level in each well), but also contains other attributes which im going to use for the Darcy Flow modelling.

Re: Spatial Intopolation using 12 points

luckyphil78 — Wed, 09 Oct 2013 05:27:41 GMT

All Good.

Figured it out 🙂

I had selected a single point and the tool was trying run on that single selected point.

Like I said, Im new to ArcGIS and will learn from this mistake.