Since the two layers have the same geographical extent, resolution and georeference you can merge the two rasters into a single raster now with 6 attributes. Then you can use a raster calculator to selectively copy certain values of vegetation index to the land use values.

Naama,

You can use conditional (con) statement in raster calculator in ArcGIS platform. Provided link below has user guide of the tool.

Kazi

https://desktop.arcgis.com/en/arcmap/10.3/tools/spatial-analyst-toolbox/conditional-evaluation-with-con.htm

you can use intersect

You did not specify the software you plan to use to perform the operation, however:

• If you plan to use a high level programming language such as Python or Matlab, you can easily accomplish what you want to do by looping through the land use array and using an if statement to check whether the current land use value matches the one you want to replace with the corresponding vegetation index value. In pseudocode this would be:

loop through the land use array

if current_value == value_to_replace

replace value with vegetation index

else

continue

• If you plan to use a GIS such as qGIS, you should be able to perform this task using the Raster Calculator https://docs.qgis.org/3.10/en/docs/user_manual/working_with_raster/raster_analysis.html or the SAGA patching function http://www.saga-gis.org/saga_tool_doc/2.2.6/grid_tools_5.html

In ArcMap, navigate to Spatial Analyst toolbar > Spatial Analyst drop-down menu > Raster Calculator. Note: Edit '-9999' to the particular value in the data to be changed to zero.

If you want to use raster calculator, try this:

Con(IsNull(raster1),raster2, raster1)

meaning that if raster1 has no value, it will use the value of raster2, otherwise it will use the value of raster1. Under the Enviroments... tab you can select your desired extent of the output raster. This will only work, if your raster1 has a lot of gaps.

However, I guess the best solution would be to use the mosaic to new raster tool in your Data Management toolbox, since you only want to replace values and not perform any other operation.

Make sure the Mosaic operator is set to your raster2, so that values from it will be used instead of raster1.

Do you have access to spatial analyst? If so, the Con function will do exactly what you want. Create a "condition" raster that is 1 where you want the values changed to Ras2 and 0 everywhere else. Execute the statements:

Ras1 = Con(Raster("condition"), Raster("Ras2"), Raster("Ras1"))

Ras1.save("Ras1")

This will replace Ras1 with your new raster. If you just want to create a new raster, change the string in the save function. If you do not have access to spatial analyst, I will see if there is a way around using the Con function.

ArcGIS 9.3.1 Raster Calculator method:

Again, assuming you have a condition raster as above.

outraster = con(condition > 0, Ras2, Ras1)

In the raster calculator, you just use the direct references rather than using the Raster function as I did for arcpy. You would then need to save your outraster and replace Ras1 with it.