Overlaying Line (Vector) Layer on Raster Zones?

Question

I am using ArcGIS 10

I have a raster layer with 3 values that make up zones. For the purpose of this example, lets say these zones are forest, grass, and open water. My whole raster is made up of these three values. I also have a line layer (it is currently a vector file but I'm fine converting to raster if I need to). This line layer is streams. I want to attach this stream layer to the raster layer based on zones. so I will end up with 6 values (Forest with stream, forest without stream, grass with, grass without, open water with, open water without). I basically want to do an overlay, but apply the stream value to the whole zone and not just a pixel. If a stream falls into a forest pixel, I want all neighboring forest pixels to also have that stream.

I really want to avoid converting the raster to vector. I looked into the zonal function tools but they seem to only give me statistics and values based on zones rather than overlay two layers based on zones.

Answer 1

You can do this by converting the streams layer to a raster, then using the raster calculator to combine the stream and zone information, e.g., make a new raster with values equal to zone + if(stream, 10, 0) (pseudocode; exact syntax will vary between platforms).

I got here looking for a way to access vector data directly from a raster calculator, but I now think that's not available in any of the standard GIS systems.