Calculation of Ground Area Covered by a Vertical Aerial Photograph

Given:

• Size of photograph: 20 cm x 20 cm


• Scale: 1 cm = 200 m


• Forward overlap: 60%


• Side overlap: 30%

Step 1: Determine the Area Covered by the Photograph

To determine the area covered by the photograph, we need to first convert the size of the photograph from centimeters to meters.

20 cm = 0.2 m

The area covered by the photograph can be calculated by multiplying the length and width of the photograph.

Area = 0.2 m x 0.2 m = 0.04 m²

Step 2: Determine the Area Covered on the Ground

To determine the area covered on the ground, we need to use the scale of the photograph.

1 cm = 200 m

This means that every centimeter on the photograph represents 200 meters on the ground.

To determine the length and width of the ground area covered by the photograph, we need to multiply the size of the photograph by the scale.

Length = 0.2 m x 200 = 40 m
Width = 0.2 m x 200 = 40 m

The area covered on the ground can be calculated by multiplying the length and width of the ground area.

Area = 40 m x 40 m = 1600 m²

Step 3: Account for Overlap

The given photograph has a 60% forward overlap and a 30% side overlap. This means that 60% of the area covered by the photograph in the forward direction and 30% of the area covered in the side direction will overlap with adjacent photographs.

To account for overlap, we need to multiply the area covered on the ground by a factor that takes into consideration the overlap.

Overlap Factor = (1 - Forward Overlap) x (1 - Side Overlap)

Overlap Factor = (1 - 0.6) x (1 - 0.3)

Overlap Factor = 0.28

Adjusted Area = Area Covered on the Ground x Overlap Factor

Adjusted Area = 1600 m² x 0.28

Adjusted Area = 448 m²

Therefore, the actual ground area covered by a 20 cm x 20 cm size vertical aerial photograph, at an average scale of 1 cm = 200 m having 60% forward overlap and 30% side overlap is 448 m².