Raster Clip attribute table contains ALL values for parent raster

[DaniMaynard]

I'm working with a large elevation raster (range of let's say 930m-2500m elevation), so I'm first clipping out my area of interest to a new raster. Upon examination of the new clipped raster the "High" "Low" values are representative of the clipped area (let's say 1300m-1500m), but when I go to set the Symbology to Classified the breaks are representative of the original dataset and not the clipped data.  When I open the attribute table, I also see the entire range of the parent dataset represented, instead of just seeing records for the clipped raster.  I've even recalcuated statistics for the clip, and it doesn't update the attribute table.

How do I get an attribute table that only represents the clipped raster, and not the parent raster?

Using ArcGIS 10 sp 2.

[PatrickTaurman]

Try the Build Raster Attribute Table tool.

Patrick

[DaniMaynard]

Wow Patrick...that worked...Thanks!

Now I wonder why a raster clip doesn't automagically do this for me?  I don't know why I would ever want the attributes of the parent raster in my clip...especially when I go to change symbologies.  Should I open this as a bug?

[PatrickTaurman]

This has already been logged, it is NIM049654 "ENH:  Please update the 'Count' field in a raster attribute table when performing a clip or add a disclaimer to the help documentation indicating that the field is not updated after the clip.".

[EricRice]

Hi Marie,

The Count field is updated after a clip operation as of 10.1 Beta 2.

Eric

[MarkZweifler]

Hi Eric:

This problem also occurs when using the "Clip" raster function available from the Image Analysis window. And for reasons that I do not fully understand it does not seem possible to use the 'Build Raster Attribute Table' tool for these on-the-fly clip rasters. After I have exported out the temp "Clip" raster function 'file' as a stand-alone dataset I can then apply the 'Build Raster Attribute Table' tool to that exported out 'permanent' raster - but that defeats the purpose of on-the-fly processing.

Do you know whether the 10.1 beta fix you mention will also address the same bug for the "Clip" raster function? (i.e after running the raster function Clip function the resulting raster should NOT contain ALL values for parent raster but only those values for the clipped out portion)

Thanks for your help

Mark

[EricRice]

Hi Mark,

In 10.1 the Clip function does not update the count field.  It's not intended to at the current time.  There is no on-the-fly recalculate field/attributes.  It's simply chipping the pixels and creating a temporary layer.  You must save it to rebuild the attribute table. 

Regards,
Eric

[WeiqiZhang]

Problem I met was that attributes gone (the option was gray) after clipping, any idea how this happen?