Question

Two points A and B having elevations of 500 m and 300 m respectively above datum appear on the vertical photograph having focal length of 20 cm and flying altitude of 2500 m above datum. Their corrected photographic coordinates are as follows:
The length of ground line AB will be

Point	Photographic	Coordinates
	x(cm)	y(cm)
a	+2.65	+1.36
b	-1.92	+3.65

• A. 575 m
• B. 535 m
• C. 565 m
• D. 545 m

Answer 1

The correct option is D 545 m

The ground coordinates are given by

$X_a=\frac{H-h_a}{f}{x}_a=\frac{2500-500}{20}\times (+2.65)=265m$

$Y_a=\frac{H-h_a}{f}{y}_a=\frac{2500-500}{20}\times (+1.36)=+136m$

$X_b=\frac{H-h_b}{f}{x}_b=\frac{2500-300}{20}\times (-1.92)=-211.2m$

$Y_b=\frac{H-h_b}{f}{y}_b=\frac{2500-300}{20}\times (+3.65)=+401.5m$

Length AB is given by

$AB=\sqrt{{(X_a-X_b)}^2+{(Y_a-Y_b)}^2}$

$=\sqrt{{[265-(-211.2)]}^2+{[136-401.5]}^2}$ = 545.2 m $\simeq$ 545 m