Arcpy.CompositeBands can't access the input datasets but the path is correct. Any ideas?

Question

I have about 30 rasters with 4 bands each that I am trying to create composites so that I can eventually bring all of the rasters together into 1 large raster. But the first step is to create composite rasters. I would like to do this all at once and I found a few examples on various sites on how to do it, including ESRI's. I've pieced them together to create my own code, unfortunately I keep getting error 000271: Cannot open the input datasets. I know the path is correct because arcpy.ListRasters() returns the files in the folder in a large list, so the problem is definitely with the CompositeBands tool. I've looked up possible solutions to this problem, but I did not understand the solutions or how they worked, so if you do have an answer or suggestion, could you comment on your code (if you write one) or answer so I know what is going on and why? About the data - they are all ERDAS Imagine image rasters with 4 image color bands : R, G, B, and whatever N is. All but a few rasters have bands named Layer_1, Layer_2 and so on. The few are called Band_1, Band_2 and so on. Here is my code:

arcpy.env.workspace = r'\\network\folder\subfolder1\subfolder2\All_RGBN'
ws = arcpy.env.workspace
outws = r'\\network\folder\subfolder1\subfolder2\RGBN_Composit'
for ras in arcpy.ListRasters("*.img"):
    name = outws+"\\"+ras
    try:
        arcpy.CompositeBands_management("Layer_1.img;Layer_2.img;Layer_3.img,Layer_4.img", name)
    except:
        arcpy.CompositeBands_management("Band_1.img;Band_2.img;Band_3.img,Band_4.img", name)

Thanks!

Answer 1

If your rasters have multiple bands, they are already composite. Composite Bands should be used when your bands are distinct raster datasets that you want to merge into one raster.

If you want to merge all your rasters (composite or not) into one single dataset, you should create a Mosaic Dataset or a Raster Catalog and load your rasters into it.

And FYI, you get an error message in the Composite Band tool because your raster bands (inputs) are not correctly referenced, you should write something like:

ras + "\\Layer_x" instead of "Layer_x.img"

But doing this will output the exact same raster as the original one.