The number of cells required to cover a given area can be calculated by dividing the total area by the area of one cell.
For ASTER-GDEM, the resolution is typically 30 m (0.03 km) per cell.
The area of one cell is:
\[
\text{Area of one cell} = 0.03 \, \text{km} \times 0.03 \, \text{km} = 0.0009 \, \text{sq. km}.
\]
Now, to find the number of cells required to cover an area of 9 sq. km, divide the total area by the area of one cell:
\[
\text{Number of cells} = \frac{9 \, \text{sq. km}}{0.0009 \, \text{sq. km}} = 10000.
\]
Thus, the number of cells required is 10000.