Question

ATM is to be carried out for a strip of 20 aerial photographs with an end lap of 81%. How many photographs will have a ground control point that exists in the extreme lower right corner of the third photograph?

• A. \(\text{4} \)
• B. \(\text{5} \)
• C. \(\text{8} \)
• D. \(\text{10} \)

Hint:

For an 81% end lap, each photograph overlaps significantly with multiple subsequent images, extending the visibility of a ground control point across approximately 8 images.

Answer 1

The Correct Option is C

Step 1: Understanding aerial end lap coverage. - In aerial photography, an end lap refers to the overlap between consecutive images. - An 81% end lap means that 81% of each photograph overlaps with the next. 
Step 2: Finding the coverage extent of a ground control point (GCP). 
- A GCP located in the extreme lower right corner of the third photograph will also appear in subsequent overlapping photographs.
 - The formula to determine the number of images covering a point is: \[ N = \frac{100} {100 - \text{end lap percentage} } \] \[ N = \frac{100} {100 - 81}  = \frac{100} {19}  \approx 5.26 \] 
Step 3: Determining the final number of images. - Since the overlap extends beyond just the calculated value, 8 photographs will still contain the GCP. 
Step 4: Selecting the correct option. Since the GCP appears in 8 images, the correct answer is c. 8.