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,

Paul

[MattDavis]

Hey Paul,

Have you tried using the "Raster Compare" tool?

If so (and to no avail) then I'm not sure how useful the following suggestion will be but I would recommend converting the raster files into a point shapefiles and using combinations of the "Point Distant" tool and/or "Spatial Join" tool (once Spatially Joined you can run field calculations on the two columns with the different values to find the points with the ranges you are looking for, once done its pretty easy to generate a raster from those points using the "Point to Raster" tool). 

-Matt

[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 points to all the points in a shape file. I don�??t have ArcInfo so I can use �??Point Distance�?�. I have ArcView with 3D and 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

[MattDavis]

Hi Paul,

Sorry for the late reply! I've been out of town at a work conference.

I dont know of any other methods without using the Proximity toolset.  I do recommend looking at

http://resources.esri.com/help/9.3/ArcGISEngine/java/Gp_ToolRef/geoprocessing/proximity_analysis.htm 

to see if there are other tools that do the same thing in a roundabout way.  There might be a way to script such a process but I'm very new to scripting and wouldn't be the one to help you with that.

Anyone else have any suggestions?

[Jean_PaulLittleton]

We have got a solution; for the difference in values between matching cells we are using Raster Calculator in special analyst, and for the distance differential, we are using the Field Calculator with a VBA Script Code to calculate the great circle distance then do the differential.

Thanks for your inputs.