I am making a map where a trigger happens when units are brought to a low ice patch. The patch is not square, so the location extends a little bit past the patch in places. I have the location set to "low ground" in scmdraft, or "low elevation" in xtra editor. With mid and high unchecked. Triggers are still occurring on the higher ground though. What's the problem?

Map is attached. Location in question is "Heroes" in dead center.

Attachments:

low ground also includes water and mates sunken and raised terrains.
Medium ground is hills (high dirt) and terrain buildings (compound)
High ground is terrain buildings on hills (high compond).

because it is the same elevation level even if it looks like lower.
-snow/ice/grass/dirt/rocky snow are lower
-high dirt/high snow/high grass/outpost are middle
-and high outpost is the highest level.

edit: damned I'm typing to slow

Read pinned topics, do what they say, and find Terrain Height wiki.