topic Re: Change values in table to no data in ArcGIS Spatial Analyst Questions

Change values in table to no data

CristinaMadrid — Fri, 01 Oct 2010 11:55:51 GMT

Hello!

I am quite new in ArcGIS. I am trying to do an interpolation of precipitation from a point shape that I have created using an XY table.

My problem is that I had to change the no data values in the original table to -9999 so when I created the point shape the program wouldn't transform it in 0.

Now I need to tell arcGIS that those points are no data, so it can do the interpolation properly.

I could solve the problem in two ways:

1. By changing the -9999 values in the attribute table into "no data". For this I have tried SETNULL but a raster is required.

2. By telling arcGIS that it should not use -9999 when I do the kriging.

Any ideas?

Please!

Thank you very much.

Re: Change values in table to no data

EricKrause — Fri, 01 Oct 2010 17:19:48 GMT

In the Attribute Table, use "Select by Attributes" in the Table Options pull-down menu. Use the equation "X > -9999", where X is the field of your precipitation values. This will select all points with values above -9999. With those points selected, run the kriging tool; only the selected points will be used in the interpolation.

There are other ways of doing it, but I think that's the simplest.

Re: Change values in table to no data

CristinaMadrid — Fri, 01 Oct 2010 17:31:01 GMT

Cool thanks!

I have actually done it with the geostatistical wizard and then convert to raster.

Interpolation is great, but I got some negatives (unlogic for precipitation). I must convert those negatives in zero now. But don't know haow. Any ideas?

Thanks again!