comparing 2 raster layers

[Jean_PaulLittleton]

Hi,
I am trying to compare 2 raster layers that are identical in size and grid resolution, based on two factors: the difference in values between matching cells, and the distance from each cell pair to two reference points located within the layer frame. In the layer properties, Format is grid for both raster layers, and Statistic has min -9999 and max is 115.10 for the 1st layer and min -9999 to max 120.4 for the second layers. Are there tools in the Arctoolbox that I can use to do this?

Assuming there are tools available, I want to compare each cell-pair to identify only the cells that have values that are similar for both layers, e.g., <10 difference between the values of both layers in the same cell. For the cells meeting the difference criteria I would determine the line of sight distance between both reference points (geographic coordinates) to each of the cells that have a difference of less than a specified amount. Cells meeting both value-difference and distance criteria would be marked in an output layer

Thanks,

[jimparsons]

Assuming your grids are vertically aligned, which is sounds like they are, you want to subtract one raster from the other. Do you have spatial analyst?

Go to spatial analyst toolbar -> raster calculator then in the comlicated box that appears, double click raster 1, double click the subtract sign (-), double click the second raster. Click evaluate.

The new raster shows you the difference between cells. Choose a symbology with a neutral color for 0, and say blue for negative and red for positive. This quickly shows you the areas that have greatest difference between the two rasters.

[Jean_PaulLittleton]

Hi,
Thank you very much; I used the Raster Calculator to subtract one raster from the other.
Now I am trying to calculate the great circle distance between a source point to all the points in a shape file. I don�??t have ArcInfo so I can use �??Point Distance�?�. I have ArcView with 3D an spacial Analyst. Is there a tool or a way to get a shape file that has distance values in Km from a source point to all the points?

Thanks.