CALCULATION OF A BLOCK OF STRIPS, ETC. 
15 
tions for altimetric adjustement are set up ; in the same time, the coefficients 
of the normal system are formed. The same procedure is followed for T points. 
As the normal system is solved, and for each stretch the 3 coefficients Acp, 
Ato, Z 0 for altimetric transformation are obtained, the transformation of the in 
strumental coordinates of all known and T points is carried out. Furthermore, 
the machine computes the residuals of the observation equations (which are the 
differences from the ground coordinates, for the known points; the differences 
between the values obtained from the various stretches, for T points). The arith 
metic mean of the coordinates obtained from each origin is then calculated ; this 
will be assumed as final computed value. 
The transformation coefficients and the residuals, thus computed, are recorded 
on a magnetic tape. 
The instrumental coordinates of the calculation points are then entered the 
storage, and are transformed by the coefficients of the stretch to which they belong. 
Finally, the following elements are recorded, stretch by stretch, on another 
magnetic tape : 
— serial number of the point ; 
— instrumental coordinates used for the calculation ; 
— transformed coordinates (for the T points, they are the mean of the values 
obtained from all stretches) ; 
— ground coordinates used for the calculation (for the known points only). 
The two output tapes are then printed off-line by means of an I.B.M. 1401 
computer. 
The actual execution of the calculation is very quick. For a block of n stret 
ches, which includes the number of points generally required for a good aerial 
triangulation, it roughly takes-«/2 minutes ; the calculation of a-block of 15 stret 
ches takes normally about 7 minutes. 
Simplified procedure. 
In view of the limited storage size of the computer at our disposal, the whole 
calculation was divided up into three separate programs, as follows : 
b) BL1 program - it performs operations a) and b) of para. 9, i. e. the cal 
culation — by the rigid-model method — of planimetry and altimetry for each 
stretch taken separately, neclecting the 7 rotation. 
The formulas used for this calculation are essentially those shown in the first 
part of Annex 1. If, in addition to the two axis points, we dispose of other known 
points, the planimetric coefficients are obtained by adjustment, by means of the 
formulas mentioned in the aforesaid Note (*), program 400. A series of automatic 
checks, based on comparison between instrumental and ground coordinates in the 
different photographic references of multiple points, evidences any gross errors in the 
determination and identification of points, or in the transcription of their coordinates.