AUTOMATIC PHOTOGRAMMETRIC INSTRUMENTS 
5 
connection with a particular stereoplotter, 
because the design of the differential rectifica 
tion equipment or the settings for differential 
rectification are determined by the stereo 
plotter to be employed. Dr. Otto Weibrecht 
of Carl Zeiss, Jena, has made new proposals 
to rectify differentially using a conventional 
rectifier with integral automatic magnifica 
tion control. His general proposal offers the 
advantage that the instrument can be em 
ployed with a variety of stereoplotters; that 
it can be used with photography of any focal- 
length; and further, that it can also be used 
as normal, plane rectifier. 
If a conventional rectifier is to be employed 
for differential rectification, as discussed 
previously, it must have an enlargement de 
pendent on terrain relief and an adjustable 
slit which can be moved strip-wise over the 
projection table with the aid of a cross-slide 
system. An additional special accommodation 
is an automatic movement of the vanishing 
point corresponding to perspective conditions. 
The necessity of coupling the differential 
rectifier with a stereoplotter also requires the 
determination of continuously variable set 
ting values for the rectifier based on the 
orientation of the stereopair in the plotter. 
Dr. Weibrecht derives and discusses the 
setting values for the differential rectifier in 
his paper, “A New Technique of Differential 
Rectification.” 
In a second paper, ‘‘A New Solution of Dif 
ferential Rectification Using the Analytical 
Plotters, ‘‘Dr. Weibrecht considers the em 
ployment of universal stereoplotting equip 
ment, and in particular the Helava Analytical 
Plotter, in conjunction with conventional 
rectifiers. The analytical plotter seems par 
ticularly well suited for such a combination 
since no special attachments are required for 
the conventional rectifier except slit-width 
control. Calculation of the constants as well 
as continuously variable setting values could 
easily be done in the computers associated 
with the plotter. Particular consideration is 
given to the coupling of the analytical plot 
ters to the Zeiss Rectifiers SEG I and SEG V 
as well as a proposed non-tilting lens rectifier 
with two axes of tilt and an image carrier 
which may be swung. Eor purposes of dif 
ferential rectification the analytical plotter 
offers the obvious advantage that magnifica 
tion control can be handled in the plotter’s 
computer. 
Magnification control is also available in 
the automatic mapping equipment to be dis 
cussed later in this paper. In many of these 
instruments an orthophotograph is produced 
as the result of electronic scanning and elec 
tronic presentation, wherein magnification 
control is more easily accomplished. Dif 
ferential rectification plays an important role 
in the automation of mapping. 
B8-Stereomat 
At the Ninth Congress G. L. Hobrough 
presented information on an instrument that 
demonstrated that automatic correlation of 
stereopairs had been achieved in principle. 
The instument, which achieved automatic 
correlation of stereopairs, was known as the 
Stereomat. Since that time there has been 
a Stereomat II, which was coupled to a Nistri 
Photomapper, but otherwise similar to the 
original instrument; and a Stereomat III, 
which employed dual scanning-tubes to over 
come terrain-slope limitations. Further de 
velopment of the Stereomat system has been 
carried out by Huntec and Wild Heerbrugg, 
Ltd., in conjunction with the Wild B8 
Aviograph. ‘‘Constructional Features of the 
B8 Stereomat,” by Dr. Wilfried Loescher, 
Wild Heerbrugg, describes this development 
from the point of view of the designer of photo- 
grammetric instruments. He discusses the 
principal considerations in adapting the 
Stereomat to photogrammetric plotters. A 
supplementary report, ‘‘Automation Char 
acteristics of the Stereomat B8,” is presented 
by R. M. De Graaf, Huntec, Toronto, who 
has carried on the electronic development of 
the Stereomat. 
Although some users of photogrammetric 
instruments looked for the development of a 
Stereomat package which could be added to 
any plotter, the designers were convinced 
than an entirely new instrument would have 
to be constructed to make maximum use of 
the Stereomat potential. However, since the 
basis for new instrument design was not 
available, it was decided to adapt it to the 
plotter which would maximize its potential 
and minimize its difficulties. The principal 
difficulties were a low signal-to-noise ratio, a 
terrain-slope limitation, and slow mechanical 
response due to the inertia of the carriage 
system. The Wild B8 was chosen because it 
could be adapted to a stereomodel scale only 
double the photo-scale with apertures 
limited only by the law of optics, thus maxi 
mizing the signal-to-noise ratio; because the 
mechanical principle permitted the use of 
separate scanning optics for the two pictures, 
thus overcoming the slope limitation by use