1 
Reprinted from 
PHOTOGRAMMETRIC ENGINEERING 
JULY 
106 ( 
Analytical Photogravimetrie 
P hotogrammetry is in the process of re 
forming its attitude toward both data 
acquisition methods and data evaluation 
techniques. 
The “classic” photogrammetric measuring 
procedure is characterized by a steadfast be 
lief that the photogrammetric camera is the 
exclusive tool of data acquisition and that 
analogue-type restitution instruments are the 
only practical equipment for data reduction. 
The corresponding hardware, produced by 
the leading instrument manufacturers, allows 
for balanced systems. This means that an 
effort was made in directing developments in 
photogrammetry to insure that specific in 
strumental components, when used in proper 
combinations, would provide an economical 
solution to a specific photogrammetric 
measuring problem. 
Thus, a closed cycle of component develop 
ment was established. For instance, an im 
provement in the resolution of photogram 
metric emulsions made it desirable to increase 
lens resolution accordingly. The resulting 
improvement of the data acquisition systems, 
in turn, resulted in the development of more 
accurate restitution equipment, thus increas 
ing the overall economy of the photogram 
metric measuring procedure. 
This cycle of evolution, which in the past 
was characteristic, has lately been somewhat 
distributed. There are quite a few reasons 
why photogrammetry is undergoing reforma 
tory changes, and any attempt to catalogue 
the areas in which such changes are occurring 
is faced with the difficulty that there are a 
considerable number of interactions among 
the various photogrammetric activities af 
fected by new developments. 
First, it appears necessary to make a 
qualitative statement about the capabilities 
of the present generation of photogrammetric 
equipment, in order to establish a norm to 
which the new ideas and techniques can be 
compared. 
Instruments 
DR. HELLMUT H. SCHMID, 
U. S. Coast and Geodetic Survey, 
Washington, D. C. 20230 
Considering the aforementioned balance 
between the capabilities of photogrammetric 
data acquisition systems and evaluation 
equipment, one must conclude that the 
present generation of precision analogue 
restitution equipment is capable, within 
operational limits of specific designs, of doing 
justice to the metric information of the pres 
ent precision photogrammetric records. The 
results obtained in production work indicate 
that the internal precision of first-rate photo 
grammetric records is limited by a random 
error range (random noise-level) of ±4 to 
± 10¡x, depending predominantly on the type 
of emulsion carrier used and the identifiability 
of target images (detail and range of contrast 
of the photographed object). 
For compatibility, a random error of per 
formance between 1 part in 9,000 and 1 part 
in 50,000 for the restitution equipment is 
essential when considering the range in focal 
lengths of 90 to 210 mm. for the photogram 
metric cameras. 
Equally important, unavoidable systemat 
ic errors, which act as perturbations (biases) 
on the concept of central perspective, and 
which are inherent in the data acquisition 
and data reduction equipment, are in the 
most accurate equipment sufficiently re 
duced so that they do not impair the sig 
nificance of the final results within the afore 
mentioned error bounds. This statement, 
however, must not be taken in an absolute 
sense, but must be interpreted in view of the 
fact that the classic photogrammetric evalua 
tion methods are essentially interpolation 
methods and can eliminate small disturbing 
bias errors in the various components of the 
photogrammetric measuring method by in 
dexing the stereoscopic model to a sufficient 
number of independently-given geodetic con 
trol points. 
Similarly, the accumulation of systematic 
errors in instrumental strip triangulation is 
eliminated by fitting higher order polynomi 
als to the results in conjunction with in