Clip 2 Grids together with NoData regions

Clip 2 Grids together with NoData regions

Post by Artur Grall » Tue, 05 Dec 2000 04:00:00

Hi All,

I have created 2 Topogrids with ArcInfo 8. The data in Grid1 has some
regions with NoData and in this NoData regions I have to "import" (or
merge, or mosaic???) the  Grid2 (just some islands of data).
The problem is to join the data in ArcView 3.2, because the Output Grid3
is always completely NoData. I used Analysis/MapCalculator and then
I guess, if NoData should be joined with data, the result is NoData.

Any Ideas to get correct results?

Best regards from Hamburg,


Clip 2 Grids together with NoData regions

Post by mapme.. » Fri, 08 Dec 2000 04:00:00


When you add two grids together NODATA always overwrites data.

The way around this is to convert the NODATA values to a value.
You can do this in ARCINFO using the ISNULL function in a con statement
newgrid1 = con(grid1(isnull), 9999, grid1)

this will convert all the NODATA values to 9999.  Do the same with grid2
and then add them.

Hope this helps


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