topic Re: Merging rasters that overlap.... ? (1992 NLCD) in Data Management Questions

Merging rasters that overlap.... ? (1992 NLCD)

RolandDeschain — Thu, 09 Aug 2012 15:07:40 GMT

Hello,

I've searched far and wide. I refuse to believe that no one has dealt with this:

I need to combine the sections of 1992 NLCD (national land cover data) into a contiguous raster. This would be easy if it were a big grid (like a DEM), but the sections are arbitrary fragments that 1) overlap and 2) contain large black areas with no data.

When I try to combine the sections together (Data Management > Raster > Raster Dataset > Mosaic to New Raster), the big black sections at the periphery cover up the real data. There is enough data to fill the gaps, but the black sections are in the way.

I know someone's dealt with this, but nobody seems to have put it up on the web. Let's be the first!

Thanks!

[ATTACH=CONFIG]16799[/ATTACH]

Re: Merging rasters that overlap.... ? (1992 NLCD)

Robert_LeClair — Thu, 09 Aug 2012 15:34:23 GMT

Roland -

I would consider using a Mosaic Dataset to reference your original raster datasets. You can order the Mosaic to control overlap so as to avoid the black pixels you're seeing. To learn more about MD - please visit http://resources.arcgis.com/en/help/main/10.1/index.html#//009t00000037000000

Good luck!

Robert LeClair
Esri-Denver

Re: Merging rasters that overlap.... ? (1992 NLCD)

CarrieDavis — Fri, 10 Aug 2012 16:23:08 GMT

Hi Roland,

If you are not able to use the mosaic dataset option, you may want test using a different mosaic operator method than the default "Last" in the Mosaic To New Raster tool. You could test these options by creating a mosaiced temp raster layer using the Mosaic button on the Image Analysis Window. This is available in 10 and 10.1.

Using the mosaic button on the Image Analysis window
http://resources.arcgis.com/en/help/main/10.1/index.html#/Using_the_Mosaic_button_on_the_Image_Analysis_window/009t000000nm000000/

Carrie

Re: Merging rasters that overlap.... ? (1992 NLCD)

chloedesgrand — Fri, 17 Aug 2012 01:35:47 GMT

Hey,

I had a similar problem, however, instead of black patches I was getting white or blue/pink overwashes. The person who replied to my thread suggested a similar thing to Carrie which was to change up the mosaic operator and colour map defaults and that worked well for me. It just might take a few tries to work out which options work best.

The reply I got to the thread I posted is at -- http://forums.arcgis.com/threads/64152-Mosaicking-to-new-raster -- if you wanted to have a look and see exactly what that person said.