pe e IN 
(393) 
THE INFLUENCE OF INSTRUMENT-ERROR ON METHODS OF 
ORIENTATION AND ACCURACY OF PLOTTING 
by 
R. Finsterwalder. 
The accuracy of photogrammetry has been increased noticeably during the 
last twenty years. Thereby it was not enough to reduce one influence of error 
but the sum of all influences. These influences are for instance the resolving 
power of the lens and of the photographic emulsion, residual distortion of lens, 
irregular film shrinkage and all influences of instrumental errors. The sum of 
all these influences has been expressed hitherto by the value of m, — — 0,05 mm 
on the original photograph (monocular measuring). Hereby precision plotting 
instruments are supposed. m, is a fundamental value used widely for general 
error-investigations. It has been often discussed, some ones were of the opinion 
it may be smaller f.i. Kasper, but on the other hand Hallert (Sweden !) tested 
the value to be larger. He found 0,051 mm in 1951. Nevertheless there was no 
great objection against the value mo = 0,03 mm. 
An import progress was the increase of optical resolving power and 
reducing resp. eliminating of lens distortion, but all the progress brought about 
the Orthometar, Topogon, Metrogon, Aviotar, Aviogon and Topar-lenses would 
have been in vain unless the photographic resolving power had been simultane- 
ously refined and the stability of photographic emulsion base improved and 
also the irregular film shrinkage reduced. An import problem is to-day whether 
film or glass should be used as emulsion base. 
The progress which has been attained is evident from the fact: whereas 
several years ago it was still necessary to use crosses Or circles one meter in 
diameter for rendering the control points visible it is now sufficient to white- 
wash only the boundary stones for precise plotting from photographs of low 
altitude (h = 1000-2000 m). Points of this kind can be located by the floating 
mark with an accuracy in excess of 0,03 mm (monocular measuring), this special 
accuracy is now at least 0,01 mm. Of the same order is the value of vertical 
parallaxes which are just visible in the reciprocal orientation. It is of greatest 
interest that one sicceeds ‘also in this case in eliminating all visible vertical 
parallaxes when orientating relatively two photographs in the plotting instru- 
ments. This experience proves also the high progress attained in the accuracy of 
these instruments. 
Instrument errors and methods of orientation. 
Even in our days the method usually employed for reciprocal orientation 
is still the optical-mechanical process of O.v. Gruber, any calculation is hereby 
avoided and results are obtained very quickly. 
But the optical-mechanical method is a little too primitive, one gets no 
figures, that is a disadvantage in some cases especially in aerotriangulation where 
1) Hallert, B. Contribution to theory of errors for the double point intersection in space. 
Transact. of the Royal Inst. of Technology 1950, see pp. 62.