Returns the approximate area of this cell in steradians. This method is
accurate to within 3% percent for all cell sizes and accurate to within
0.1% for cells at level 5 or higher (i.e. squares 350km to a side or
smaller on the Earth's surface). It is moderately cheap to compute.
Returns the approximate area of this cell in steradians. This method is accurate to within 3% percent for all cell sizes and accurate to within 0.1% for cells at level 5 or higher (i.e. squares 350km to a side or smaller on the Earth's surface). It is moderately cheap to compute.