INDIA 4 
A large amount of aerial triangulation in space has been carried out in the photogrammetric 
instruments since 1958 and Table 3 gives the aerial triangulation in space performed in the Survey of 
India during the period 1960-64. 
Table 3.—Aerial triangulation in space in India during 1960-64 
Area in 
sq. km 
Scale 
No. and length 
of strips 
Long Med. Short 
No. of 
stereo- 
• pairs 
Remarks 
Survey of India 
1. Departmental Survey 
1,27,184 
1 : 50,000 
215 96 61 
5042 
2. Development Project 
Survey 
308 
1 : 10,000 
11 
200 
Adjustment of aerial triangulation.—In India, the adjustment of aerial triangulation is generally 
carried out by the graphical Interpolation method of strip adjustment of Zarzycki. The requirement 
of desirable minimum ground control for the adjustment of an aerial triangulation strip is five points 
in the first model, three points in the middle and three points in the last model of a strip. To start 
with in 1958-59, the strip lengths were restricted to about 10 models so that in every fifth or sixth 
photograph of a strip, ground control points determined by normal field surveying methods were 
used. 
Subsequently, a further reduction in the number of ground control points was achieved by the 
introduction of tie-strips. These tie-strips are flown in a direction perpendicular to the direction of 
the filling-in strips at about 8 to 10 models apart for topographical surveys and ground control points 
are required to be provided in the tie-strips only, though primarily of the same 5-3-3 pattern as in a 
normal strip. In this method, tie-strips are aerially triangulated first to provide the necessary start 
ing, middle and last model control points for the adjustment of each filling-in strip. The main short 
coming of this method is that no advantage is being taken of the inter-relationship between the adjoin 
ing strips. 
Block adjustment gives a more homogeneous and accurate solution and we have recently 
acquired the I.T.C. - Jerie Analogue Computer Block Adjustment equipment for this purpose. 
I.T.C. - Jerie Analogue Computer is a simple mechanism capable of yielding consistently accurate 
results employing relatively less-skilled personnel and has none of the complexities of a purely analy 
tical adjustment using electronic computers. The various stages of the adjustment procedure are 
performed by survey personnel already available with us, after a short training. The I.T.C. - Jerie 
analogue computer is based on the principle of least squares which ensures high relative accuracy 
and the requirement of ground control points is drastically reduced when the block adjustment method 
is employed. 
' * " ' l ,-i 
In most of the cases, the adjustment of strips is carried out based on minimum control only 
for economical reasons. The accuracy of strips are worked out in cases where scattered redundant 
ground control points are available and have been identified on aerial photographs, i ■ ■