New Photogrammetric Plotting Instruments 
H. Kasper, Heerbrugg 
Numerous pictures were taken with the new Aviotar Objective at various places during 
the past four years. In plotting from these photographs on the WıLD A5 Autograph, 
accuracies were obtained which were barely considered possible when the last congress 
of Photogrammetry was held. 
Manewhile, further progress in the field of photogrammetric optics has been achieved 
through the creation of a wide angle lens having photographic qualities equal to those 
of the Aviotar. This lens is the WiLp Aviogon f/5-6. It will probably make the use of 
aerial or strip radial triangulation increasingly possible in photogrammetric practice. 
Obviously, therefore, the plotting instrument required for this purpose, the Wirp A5 
autograph, had to be investigated, in order to ascertain whether it could not be equip- 
ped better than in the past for the specific purposes of aerial triangulation. 
While carrying out these changes, the wishes of the English speaking users had to be 
met, by making possible the direct utilization of the popular 9" x 9" format. 
Bearing in mind the outstanding results obtained with the A5 Autograph, we had to 
convince ourselves about the very possibility of improving on it. 
Thus it was that, once more, we meticulously studied the mechanical design and the 
optical system of the machine, its stability and precision, as well, in fact, as all features 
making for practical usefulness, particularly economical aerial triangulation, and the 
results of this study were embodied in the design of a new plotting instrument, the 
Wirp A7 Autograph. 
Now, both the new design and the A5 model are based, as to their overall design, on 
the principle of mechanical evaluation, its universality and precision being unsur- 
passed. The same applies to the convenient frontal observation, which no user would 
want to miss. On the basis of research and long experience in building plotting in- 
struments, we decided on the following constructive measures: 
The larger picture size requires, in the first place, a reinforcement of the base plate and 
furthermore justifies some fundamental changes in the mechanical construction. The 
camera frames, in the A5, are suspended on a vertical axis, but those of the new 
design instrument rest on a very solid main frame or yoke. 
In the A 7, the degrees of freedom of the cameras and base were limited to those barely 
necessary. 
The rods used in the linkage, which became heavier and longer due to the increased 
picture size, are no longer of the cantilever type, but rather guided along an adjustable 
rail segment at their free end. Therefore, there is no reason to fear any bending or 
accidental errors due to elasticity.