Handbook of Civil Engineering Calculations

Calculation Procedure:

1. Compute the flying height with reference to the ground
   Take the ground as datum. Then scale S = ftH, or H = flS = 0.2101/(1/10,80O) =
   0.2101(10,800) = 2269m.


2. Establish the relationship between height of tower and
   distances in the photograph
   Let g = height of tower. In Fig. 30, oa/D =//(# - g) and ob/D = JJH. Thus, oa/ob =
   (H- g). Solving gives g = H(I - ob/oa).


3. Compute the height of tower
   Substituting in the foregoing equation yields g = 2269(1 - 71.68/76.61) = 146 m.

(a) Elevation normal to vertical plane through

optical axis and center of tower (plane V)

FIGURE 30

Ground

Datum plane

Plane of

photographh

(b) Plan

Plane V

Opticalaxis