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