Raster tiles do not match up?

[jamiefisher]

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Okay, I have a load of tiles showing the elevation of the land. As you can see from the picture, the tiles do not match. How do I solve this?
I managed to get them matching when I changed the stretch type of each tile to min-max and the altering the values. However I am unsure of this.
I am quite sure there is a very simple solution, but I am awful with the software.
Any help would be great.

[JakeSkinner]

Hi Jamie,

I would recommend creating a mosaic dataset of the raster datasets.  You can then calculate statistics on the mosaic dataset.  This will calculate statistics as if all of the rasters were one seamless image and you should no longer have this problem.