■13-
length of one of the base board margins a 10 x 20 cms grid, 40 cms
wide, was plotted. The center lines of the 1/20.000 control perma-
trace bands were then aligned on the central axes of the grid on the
board and the adjacent 20 cm grid points transferred. Similarly
the axes of the double size bands were aligned and the outer 40 cm
grid points transferred.
The auxiliary grid points thus obtained were used on
the scale transformation of the slotted templet control described
later.
6. 3 - Rectifier settings for 2x enlargement
A 40 cm square was plotted on a piece of vinylite, using
the A-7 coordinatograph. In order to avoid any possible backlash
and eccentricity of the steel point holder, the final movements of
the handwheels were always in the same rotation sense and the pri
cker kept in unchanged position.
The Wild E-3 rectifier was then adjusted by means of
an A-7 grid plate, establishing the correspondance between the 20 cm
glass plate square and the 40 cms square projected on the vinylite,.
Thus the 5 freedom degrees of the rectifier were set to
enlarge twice.
All the 4 points coincided perfectly, which proves the
good quality of the E-3 optics.
6,4 - Enlargement of the radial triangulation control to l/lO.QOO
With the rectifier in the previously determined posi
tion, all the 9.5" wide permatrace bands were worked ou,t as if
they were films and so all the slotted templet control - 1/20.000 -
was enlarged to l/lO.OOO.
The orientation of the 20" wide bands on the easel ta_
ble, was done successively for each set of nine points - correspond
ding to a photograph - on the carry over points.
The axes and auxiliary grid points were kept as much as
possible in coincidence, to prevent cumulative errors.
It was found necessary to ink in the slotted templet
points on the 9".5 transparent bands.
Although 6-12 meters long bands were used - scales
1/20.000 and l/l0,000, respectively - the results obtained can be
considered acceptable, as will be referred to later on.