After merging rasters, information seems to have change.

Question

Hello

I have traditionally used the "Mosaic to New Raster" function to merge Digital Elevation Models (DEM) rasters. I realised that once merged, the values tend to be slightly different compared to the inputs (e.g. two input rasters with elevations between 177-6851 and 133-6594 producing an output raster with elevation values between 93 and 6868). I have merged them in several different ways, but I always find a difference between input and output values. I also tried to use other functions but have not been able to find another one that does the similar task. Could someone give me an idea of how to correct this or at least understand why does it happens and what does it mean. Also, if someone knows another function that does the similar job I would appreciate you could let me know the name.

Hope someone can help me with this

Thank you very much in advance

Regards

Juan

JuanOssa · Answer

The colours do change but as I was comparing the numerical values I think that the differences may go beyond the colours. I double checked the cell size, coordinate system and extensions of layers, and it seems that the problem is not there. Thanks for the links! Will try this function!

DanPatterson_Retired · Answer

I imagine that it has to do with the matching of the raster colormaps since your two inputs are different.  ArcGIS Help (10.2, 10.2.1, and 10.2.2)   What are the details of the results versus the various options that you have chosen.  Pay attention to cell size, whether there are overlaps or gaps and the original colormaps.  You might want to consider Add Rasters To Mosaic Dataset—Help | ArcGIS for Desktop  as a first look as well