topic Re: Raster Layer Help..... Slopes in Data Management Questions

Raster Layer Help..... Slopes

GreggPawlowski — Thu, 29 Jul 2010 18:28:29 GMT

I have a raster layer containing slope percentages that is displayed as a color ramp. I'm trying to display ranges of slopes instead, ie 10-15%, 16-25% and >25%. If I go to the layer properties symbology tab and try to "show" CLASSIFIED instead of STRETCHED Arcview tells me I dont have a histogram and asks if I'd like to compute unique values. I click yes but then I get an error saying that there are too many unique values (> 65,000).

The Raster Dataset that I'm using covers about 6,000,000 acres. Is there a way I can trim out or export just the data that I need? I only need about 100,000 acres of the data.

Sorry if my terminology is incorrect as I'm not very experienced in this aspect of Arcview. Thanks in advance for the help.

Gregg

Re: Raster Layer Help..... Slopes

EricRice — Fri, 30 Jul 2010 15:49:25 GMT

Hi Gregg,

You can try increasing the number of unique records to render by going to ArcMap Main Menu > Tools > Options > Raster > Raster Attribute Table (subtab) and increase the value from 65,536. If you using ArcGIS go to ArcMap Main Menu > Customize > ArcMap Options > Raster > Raster Dataset (subtab) and at the bottom you'll find the same parameter. Set it to something very high like 1 billion.

If your still interested in clipping out a smaller portion you can go to ArcToolbox > Data Management Tools > Raster > Raster Processing > Clip.

Regards,
Eric

Re: Raster Layer Help..... Slopes

GreggPawlowski — Mon, 02 Aug 2010 10:45:56 GMT

Thanks for the help Eric. ArcMap crashed when I tried the first method you described but I only tried it once. The second method worked great though.

Gregg