The only way to explicitly set an elevation is one point at a time, setting the elevation down to zero and then up to the desired value. It would be a nightmare to try to accurately duplicate real world elevation data. Also note that the map display can be quite deceptive. Objects and vehicles are all bitmaps that don't change size. The actual location in the game will overlap the bitmap at some point, but you don't really know where until you've gone back and forth to the game to see.
Buildings are particularly difficult to judge without loading the game.
Also, while in the game there are rectangular tiles and on the map in the editor there are rectangular tiles that correspond as far as ground texture, the elevation on the map indicates the elevation of corners between tiles in the game. For example, a road will have a row of tiles one square wide in the game and for textures, but the elevation needs to be the same two points wide for the road to be flat - if you change the elevation in a square that appears to be next to the road, you may actually tilt the road up in the air. Conversely, a ditch that appears to be one square wide on the map will be two squares wide as far as textures go, because it is the point between two squares that is low. In the Desert deciduous trees become palms and evergreen trees become shrubs. The map display always shows springlike colors and the same two kinds of trees.