tif. georeference images not recognised in image analysis

[SophieCosstick]

Hi,

I have two images a GLOBCOVER and MOD44B image, both have been georeferenced to the same projection of WGS_1984 and i wish to compare the spatial extent of vegetation cover in the two images. However when i attempt to use the image analysis tool in arc map 10. when i select the layers it does not allow me to perform any function such as the difference tool as the icons are not available. Is there a way to make these avaiable?

thanks

[RobertBerger]

Greetings,

There is certain validation that happens when you select your layers. I believe for difference to work you will need two single band images. So, you could either extract the individual bands that you want to compare, or merge the multispectral into single band products (e.g. using NDVI) and then compare that.
Does that help?

Robert