vector groundVector = llGround(ZERO_VECTOR); // ZERO_VECTOR because I want to find the ground vector directly under me

float groundHeight = groundVector.z; // Now get the height part of that vector

vector myPos = llGetPos(); // Next, find my own position...

float myHeight = myPos.z; // ... and find the height part of that

float myHeightAboveGround = myHeight - groundHeight; // The difference between the two, is how high I am above the ground

if (myHeightAboveGround > 1.0)
{
  llSetPos(llGetPos() - <0,0,1.1>);
}
}