For corridor mapping projects flight lines are in different directions and when a DEM is created from a .las file, Terrain Prep Tool triangulates across large areas that is not mapped. When converting a .las file to a raster DEM in Terrain Prep Tool, can we tell it to not create triangles over a certain length?
Go to IMAGINE->File->Preferences. Preference editor will launch then under applications find surfacing options and reduce the Maximal TIN linking distance. And repeat your .las->DEM conversion In Terrain Prep Tool.