c_trace(my.x,vector(my.x,my.y,my.z-200),IGNORE_ME | IGNORE_PASSABLE);
if(trace_hit && target.z > my.z+my.min_z-10)
{
I'm on the ground, respectively floating 10 quants or less above the ground. Some kind of a height buffer is usually a good idea to avoid the computation of unnecessary collisions.
my.speed_z = 0;
}