Moved to contributed library quesions, because a contributed library is required to run your code.

The problem/fact is that you have one single float variable xR. You change this variable many times with line 55 inside a triple for loop. But you don't use it within that for loop. So at the end of all these changes, it has one value: the last value it was set to. That value is used inside a double for loop later on, in line 75, where you actually use this single value xR for every ellipse.

The solution is to either use the data directly (aka in the first for loops) or store the data in arrays/objects so you can use it later.

Thanks.  That's definitely pointing me in the right direction.  Follow up: how do I get the elevation (xR) array to iterate through all it's values while in the gridX, gridY loop?