14
GIUSEPPE BIRARDI
between planimetry and altimetry is negligible, due to the small angle between
the axes Z and Z' ; this hypothesis generally occurs in practice.
The calculation program envisages the following maximum dimensions :
— 30 stretches, each including :
. 20 known points,
. 25 T points,
. 50 calculation points ;
— 500 known points in total, in the ground system.
The storage size, however, would allow to raise up to 50 the number of stret
ches ; the corresponding 1 : 25,000 coverage is about 2500 km 2 .
First, the ground coordinates of the known points are stored. Then, the in
strumental coordinates of all observed points are loaded ; the group of coordinates
relative to each stretch is preceded by a heading card containing some data which
are common to all points of the stretch itself (false origins, sphericity coefficients,
etc.).
Each point is identified by a serial nunber, whose last digit indicates its class
(digit 1 for known points, 2 for T points, 3 for calculation points) ; as the machine
reads the serial number, it carries out an analysis to establish its class. According
to the result, the following procedures take place :
— known point. The serial number coincident with the point’s number is
sought for in the storage area where ground coordinates are contained ; the cor
responding ground coordinates are stored in another storage area, in correspondence
with the instrumental coordinates. The two observation equations of planimetry
are then formed, and the normal system is incremented with the coefficients and
the known terms. If among the known points there is not a serial number equal
to that of the point under examination, the latter is handled like a calculation
point ;
— T point. Instrumental coordinates and serial number are stored in a
proper storage area, large enough to contain all T points ;
— calculation point. Instrumental coordinates and serial number are stored
in a proper storage area.
Once the storage of all points of a stretch is completed, the contents of the
storage area concerning known and calculation points is transferred on magnetic
tapes.
As soon as the storage of all stretches is completed, the machine selects, for
each T point, the corresponding point in the other stretches by the serial number ;
then, for each couple, the observation planimetric equations are formed, and
their coefficients and known terms are added to the normal system. This is
solved, and for each stretch the 4 coefficients a, (3, X 0 , Y 0 and the scale factor
s are obtained.
When the planimetric adjustement is completed, for each stretch the known
points coordinates are entered from the magnetic tape, and the observation equa