I am new to Blender and have problem creating terrain surface for laser slicing. I have several publicly available terrain surfaces. The surfaces have some overlapping, but the overlapped faces are not same on both surfaces..  

I finally want to have an object similar to below without internal surfaces

I tried to extrude individual surfaces, and join. There are internal surfaces remained.

I tried to extrude individual surfaces, and do boolean operation: Object A union (Object B difference (Object A intersect Object B)). There are still internal surfaces.

Can anyone tell me how to do?

Jimmy

I tried to cut the overlapped surfaces by bisect tool at a specific coordinate (say at certain y) on both surfaces, then extrude and join. but there are still internal surface.

I am trying to create a terrain surface for laser slicing. I have several publicly available terrain surfaces. The surfaces have some overlapping, but the overlapped faces are not same on both surfaces. 

I finally want to have an object similar to below without internal surfaces

I tried to extrude individual surfaces, and join. There are internal surfaces remained.

I tried to extrude individual surfaces, and do boolean operation: Object A union (Object B difference (Object A intersect Object B)). There are still internal surfaces.

Can anyone tell me how to do this?

I tried to cut the overlapped surfaces by bisect tool at a specific coordinate (say at certain $Y$) on both surfaces, then extrude and join. but there are still internal surface.