Difference between a map based grid and a grid

[ASW]

Hello,

I imported a dxf from autocad in order to create a grid based map. Now that I have the map based grid I wanted to have my borehole elevations match up with these new elevations. I went through the case study on adjusting DEM grids to fit measured elevations but when I tried to get the residules I got an error saying that I didn't have a grid. Is there a differece between a map based grid and a grid and if so can I turn my map based grid into grid? Thanks.

[ASW]

Thanks for the help. Now I have another question. I created a grid based off the residules and then used the grid math function to add it to my original grid. Now that I have this new grid, I tried to use it for my lithology model. In the lithology model I selected upper surface (grid) filter and used the grid I just created. The problem is my surface displays as completely flat. I also created a section from this and got the same problem.