CHAPTER II
PLOTTING INSTRUMENTS
From the 20 precision plotting instruments reported, 25% are of new -
acquisition, these are 1 STK 1, 4 A-7 (CETENAL), 1 A-10 (AFGSA)
Mechanical instruments for medium scale work had an increase of 350 %
20 Stereosimplex IIc (CETENAL) and 1 B-8 (AEROCARTO)
A few projection type instruments were bought, some of them for training
purposes.
The use of approximate instruments in topographic mapping is close to -
zero, some of them are used to transfer photointerpretation data from -
prints to maps.
"Semi-rectified" mosaics were still used extensively but a limited activi
ty in photographic restitution is going on. By now, exact rectification and
ortophoto techniques are envisaged for mass production of photo maps, -
in suitable terrain.
CHAPTER III
AERIAL TRIANGULATION
Most of the aerial triangulation was done with the aeropolygon method.
About 53 000 models were adjusted graphically. Block adjustment is - -
mainly done at CETENAL, (18 000 models) where nine points numerical
relative orientation is done with the help of electronic desk computers -
and adjustment is done for blocks of 300-400 models using polinomical -
equations (Schut).
Presently the production of aerial triangulation is shifting to semi analy -
tical and fully analytical methods.
For ground control, geodetic points of sharp definition are used in most -
cases, at very large scales prepaneling has being done.
Traverses with the help of electronic distance measurements had a clear
predominance over triangulation and even trilateration methods.
The levelling technics have not shown important changes, although the - -
use of automatic levels have rendered more efficiency in field work.
