Can now edit and save map changes.
Found out what one of the unknown fields are.  It is a reference to a tileset that is not yet known.  Needs to be reverse engineered.
Also found out what the last tile is.  It is a marsh.
Added a button to 'reset' the height of all terrain.  Not sure if it works yet.
Have confirmed that I can change ocean to land and use that land.
To use the editor, left click will change the density.  Look in the status bar as you left click drag.
Right click will chnage to the new terrain type.