Combining 2 DEMs - adding a mine pit to existing DEM

[IeuanHarry1]

I have 2 separate DEMs which i wish to combine. One is the current DEM and the others are satellite pit designs. I am trying to add the pit designs into the current DEM so that it will represent the future DEM. Both are currently in dxf format. I have tried creating surfaces for both then using the Mosaic to new raster to join the two (selecting the pit surfaces to define the overlapping areas). The problem with this method is that it tends to lose the detail of the pit slopes.

is there any other method that can be used to combine the two?

Is there a workflow using TINs that will work?

thanks

[IanMurray]

Is the pit detail really being lost or are just not as pronounced now that the symbology is based on a larger range of values?  If the pit was a seperate DEM, then it would have a smaller range of values(perhaps) then when it was combined with the other DEM.  Since your symbology is more stretched now, it may not seem as defined, even if the values are still the same.  The other potential problem is if the DEMs are different resolutions, the Mosaic will default to the coarser resolution.