make sure min/max lat/lon works even when data is added in the grid before
make sure min/max lat/lon works even when data is added in the grid before

Caoimhinmg/PmagPy,lfairchild/PmagPy,lfairchild/PmagPy,Caoimhinmg/PmagPy,Caoimhinmg/PmagPy,lfairchild/PmagPy