9 
where : 
vt * [ v ‘ v * ••• v 3 
B* = [bÎ b1 ... B*] 
C, 
0 . . . 0 “ 
c 
0 
c 2 ... 0 
0 
0 • • * C n_ 
5t - 
[* 
D 2 ... D n j 
rt = [ f " f " ••• f 3 
Equation 3.04 represents the system of observation equations for a sub 
block. The number of unknown parameters included in the system depends on 
the method selected for sub-block triangulation. In the following sections 
an account of the new methods is presented. 
3.3 Methods of Sub-Block Triangulation 
The absolute solution of a 3x3 sub-block to the ground 
coordinate system requires a minimum of two horizontal control points and 
three vertical control points. It is hardly practical to assume that there 
would be such an amount of control available in each sub-block of a project 
area. More likely, the available control in the entire block would be of 
the same order of magnitude as that required for one sub-block. The 
following two solutions are, therefore, suggested for such practical cases. 
3.3.1 Sub-Block Extension 
This method is a further development of the well-established 
method of cantilever extension in strip triangulation. Essentially, it is 
an extension of control in two directions rather than in one. It is 
assumed that ground control, enough to absolutely orient one sub-block, is