topic Re: Noisy Natural Neighbours in ArcGIS Spatial Analyst Questions

Noisy Natural Neighbours

BenLeslie1 — Tue, 16 Jun 2015 07:52:12 GMT

I get bad results when using the Natural Neighbors tool. I think it may be a bug in 10.2.

I found an old workspace from 4 years ago that will have been created in arc9.3.

It contains a raster created using the Natural Neighbor tool - it looks good, nice and smooth - as shown below.

However if I re-run the analysis, now in 10.2, from the Results tab using the same data I get all these rogue pixels - as shown below. I have struggled with this problem for a while and basically stopped using Natural Neighbors but I now think I have proof that it is a software fault and nothing to do with my data or settings. Does anyone else have this problem or any possible solution that will fix the Natural Neighbors tool?

Although these errors are small, they do produce unwanted and unacceptable hillocks when the raster is converted into a surface.

(images adjusted in photoshop to increase constast)

Re: Noisy Natural Neighbours

DanPatterson_Retired — Tue, 16 Jun 2015 08:20:10 GMT

Are the pixel values different?

Any slight changes in the symbology levels?

Re: Noisy Natural Neighbours

BenLeslie1 — Tue, 16 Jun 2015 08:43:55 GMT

Yep the difference in pixel values in this example is around 0.5m - unfortunately this is enough to show up when the rasters are converted into terrain. This used to be a tried and tested method for us but I always get this noise in Natural Neighbours results - unfortunately I only joined the company at the point of upgrade to Arc10 and have no prior experience of Spatial Analyst so it's difficult to be sure if the upgrade is the poblem - but it seems likely to me.

Re: Noisy Natural Neighbours

DanPatterson_Retired — Tue, 16 Jun 2015 11:59:38 GMT

In a case where you can't directly compare the results of pre and post version, you should ship off a copy of your data with full details and see if tech support can replicate it. I could find nothing obvious in the NIM/BUG reports to indicate anything specific to NN interpolation

Re: Noisy Natural Neighbours

SteveLynch — Tue, 16 Jun 2015 14:34:38 GMT

Ben

Please zip the input data if you can and email it to me (slynch@esri.com). Also, what cell size are you using, what field are you interpolating on and are you setting any Environment parameters?

Any idea if any Service packs were applied to the 9.3 version?

-Steve