Fig. 19
The B8 Aviograph can be
combined with a pantograph for
plotting at up to 2% times
model scale.
The model scale in the B8 extends to 2x the picture scale. For technical purposes and for map revision
work a further enlargement of the picture scale is desirable for plotting. A linear pantograph attached
to the plotting table, makes it possible to achieve an additional 2.5 x enlargement, thus permitting
a total enlargement of 5 x from picture to plotting. A light but stable plotting table is screwed to the
instrument to provide the extra drawing surface (Fig. 19).
In the B8, the original negatives or diapositives at 9" x 9" are used directly for plotting, and the normal
correction plate carriers of the A7 and A8 are used for correcting residual distortion and earth cur-
vature. Plotting from diapositives is more simple since during the printing process, the distortion and
earth curvature effects have been eliminated (Preparation of diapositives in U3A or U4A Printer).
The orientation elements in the B8 are the same as in the B9.
The B8 is particularly suitable for training operators due to its compactness and its simple mani-
pulation.
The use of super wide angle photography in practice
A particular advantage of the super wide angle lens with a 120? angular field is that, by comparison
with wide angle lenses, the same negative scale is produced from a lower flying height. Assuming
that the super wide angle lens for 9" x 9" picture size has a focal length of 9 cm, it will be seen that the
flight heights are in the ratio of 3:5 for the same negative scale, while from the same flying height, the
super wide angle photograph covers an area three times greater than the wide angle picture (Fig.
20, 21, 22). For negative scales between 1:60000 and 1:90000, from which a map at 1 :100000 is to be
plotted, the flying heights will be chosen between 9000 m and 13500 m (30000 ft and 45000 ft) above
ground for the wide angle camera, compared with only 5400 m to 8100 m (18000 ft to 27000 ft) for the
120? lens.
