It is c_trace, not c_scan that you are looking for.
In the manual in the topic c_move, there is a movement code with c_trace used to know the altitude of the entity.
That should you give at least a better idea of how it should work.

http://www.puppenheim.org/
http://www.wuerfels-welt.de
Old Game Tutorial: http://www.puppenheim.org/MITutorial.zip
Free Game Editor: http://puppenheim.org/AlienalsWeihnachtsmann.zip
http://www.puppenheim.org/blender_starting_main_settings.txt