VIII, THE TREATMENT OF STRIP AND BLOCK TRIANGULATION 
It has been shown that the matrix of normal equations: (55), illustrated in 
Fig. 15, expresses the general photogrammetric problem. The contents of that 
matrix include the solution for the triangulation of an unlimited block and 
obviously, as a special case, the triangulation of an unlimited strip. 
Such matrices resemble each other in the geometric arrangement because 
successive groups of ground points are being photographed from a certain number 
of successive camera stations. This fact is reflected in the arrangement of - 
the coefficients in the BI (AP lA)" Bg matrix and its transpose. These 
matrices are only partially filled, forming an escalator pattern as shown in 
Fig. 15. 
The example is a strip with 2/3 overlap, where it is assumed that six 
points are located in each trilap-area on the ground (I, II ..... N). The 
corresponding reduced normal equation system (37) itself becomes & symmetrical 
escalator matrix, grouped along the main diagonal as shown in Fig. 16, 
Fig. l7 shows a reduced normal equation matrix for the determination of 
the corresponding Ay vectors of a block of 7 x 7 photographs flown with 2/3 
longitudinal and 2/3 lateral overlap. In this way, each portion of the ground 
1s being recorded on nine photographs. In the example it was assumed that one 
point is located In each one of the nine times covered ground sections. The 
matrix as shown in Fig. 17 is typical in its arrangement for any block tri- 
angulation. | 
The. size of the cross shaped openings which are filled with zeros obvi- 
ously increases with an increase in the length of the sides of the block under 
consideration. 
If one uses the aforementioned schematic of the general solution, present 
day electronic computers allow, without undue difficulties, the formation of 
the reduced normal equation systems as presented in Figs. 16 and 17, However, 
the problem remains to invert these normal equation systems. Generally 
speaking, both strip and block triangulation will result in normal equation 
systems with too many unknowns for direct inversion. 
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