1

I currently have a fairly large raster (1000, 1000). I have a vector layer of reservoirs. I need to create a 100 m buffer around the reservoir, assign it a land use code and merge it with the larger raster.

I have created the buffer, converted the buffer to raster and then classified it using my land use codes. I then used the mosaic tool to merge the two raster layers. I end up with something like this. The raster layer for my buffer, is a large square and doesn't cover the area of the buffer.

I am wondering if this is because my original raster is so large and the buffer is so small?

What is the best way to go about, creating the buffer, assigning the land use code and merging it with the larger raster?

I am using ArcGIS for Desktop and have access to Spatial Analyst.

enter image description here

1

You wrote:

I am wondering if this is because my original raster is so large and the buffer is so small?

YES ... I believe that is precisely it. It looks like the orange part is about 3 cells. The piece of the buffer outside that area would make up less than half of each cell and therefore it is using the values from the original Land Cover for those cells (default). There is not much you can do about this unless you really want to override those cells.

If you plan ahead when you create your output from converting the Buffer to a Raster, you can make it the same size as the original land cover AND also set it as the "snap raster" in your Raster Environments, that will probably solve the problem altogether. I see there is a parameter called "FIRST" that will give priority to the first raster dataset mosaicked into a given location

If that does not work (and I really think it will) and you really do want to override that you could do something with the Raster Calculator (like the "Con" tool?) in Spatial Analyst to say if the value for reservoir (say 1) in the update raster is == 1 (equal to 1), use that value, otherwise use the value from the original land cover. I think that would work to override those values. I'd make sure the cell size for both rasters matches too so that the values from the update raster effectively override the values from the original (land cover) raster. I really only included this because I wasn't sure how Mosaic knows which raster to give priority to (obviously you want to give priority to the reservoir; what I'm calling the "update raster"). I added that bit about the "FIRST" parameter and I really think that is the way to proceed.

  • Thank you! I ended up re-sampling the original raster to a cell size of 25, converting my buffer polygon to a raster using the same cell size and then mosaicking using the reservoirs as FIRST. This seemed to do the trick. – Ash Aug 24 '16 at 20:04
  • You are welcome - If that fixed the problem, you can select the checkmark (currently gray) and make it green. Thanks. – jbchurchill Aug 24 '16 at 20:19

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.