Let us say for instance that the area you selected for export to a txt file was 100 cells X 100 cells.
When you come to Import the area you want it centered on your map
Now, the map is 256 X 256 cells.
The first cell is the bottom left corner (cell 0,0) to the bottom right corner (cell 0,255). Making 256 cells on the bottom row.
Next row begins (cell 1,0).....etc etc......till the top row (cell 255,0) to (cell 255,255)
When the requester for importing pops up you will need to type in the details:
Rect section:
This is the area you want you import to go to, it denotes the bottom left corner of the import area.
Approx ........Left:78.........Bottom:78
The Width and Height sections refer to the width and height in elevation points.
Basically, assuming you exported 100 X 100 cells, you will need to put 101 into each of these gadgets, because a grid of 100 X 100 cells equates to a grid of 101 X 101 elevation points.
The Num of Coord should read 3, as should the Elevat index.
The Decimal point should be set to a period ( . ).
I presume you are importing to a New blank map here.
Objects are NOT imported also, just the terrain.
Hope this helps.
Planck