23 
Special Publication reprinted from: 
Nachrichten aus dem Karten- und Vermessungs wesen 
Reihe II: Deutsche Beiträge in fremden Sprachen — Heft Nr. 18 
Verlag des Instituts für Angewandte Geodäsie, Frankfurt a. M. 
s often needed 
lethods are not 
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were destroyed 
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ed hereinafter, 
etrically deter 
On the Accuracy of Orthoprojector Maps 
By Hermann G. Neubauer, Frankfurt a. M. 
This article has been published in German in the publications of the “Nachrichten aus dem Karten- 
und Vermessungswesen — Reihe I/Heft Nr. 30“. 
In July 1964 four photomaps have been prepared in the Carl-Zeiss-Werke at 
Oberkochen for a first study of accuracy. For this test a GZ 1 Orthoprojector with 
direct coupling to a C 8 Stereoplanigraph was available (see Ahrend, Brucklacher, 
Meier, Utz: “Der Orthoprojektor Gigas-Zeiss“. — Bildmess. u. Luftbildwes., Berlin 1964, 
3, pp. 153—160). 
is mean square 
For the test aerial photographs 1 :8,500, taken by a Zeiss Camera RMK 15/23 
have been used. The photomaps are in 1 :3,000 scale, each covering an area of 1.2 
11 increase the 
•rain (as trees, 
procedure will 
e first time in 
square km. The aerial photographs cover two neighbouring areas. The maps 1 and 2 
have been prepared from area 1 by means of negative 18 with equal orientation on 
equal conditions. Map 3 covers area 2 of the same negative. Map 4 has been made from 
negative 20 and covers again area 1. Each photomap had been produced in about 2 hours 
without orientation. The width of the adjacent profile strips (the moving diaphragm) 
was 4 mm. 
differentially 
:ting geologist, 
e map. 
The terrain shows differences in elevation of up to 250 m, i. e. up to 20% of the 
flight altitude. The slope is 20% to 30% in agricultural areas (to which the data of 
accuracy refer) and up to 80% in forest areas. Thus the chosen terrain approximately 
ojector. I feel 
'hotoscopes he 
ich a develop- 
shows the most unfavourable conditions appearing in an agricultural area, if we neglect 
terraced areas. 
For the investigations of accuracy we had 56 to 68 signalized points at our dis 
posal on the maps, the mean square coordinate errors of these points being less than 
± 3 cm. Therefore the terrestrial coordinates of these points can be considered to be 
free of errors for our plottings. The points marked on the maps were tapped off by 
means of a Coordinatograph and transformed into the national system. In order to 
determine the elements of transformation all available points have been used. The mean 
square errors obtaind by Helmert transformation (linear-conformal) have values which 
exceed those obtained by affine transformation by only about 3%. This proves that 
the photomaps show no notable affine distortion, and that the Coordinatograph has 
no perceptible spindle defects, nor angular errors. Hereinafter we consider the errors 
after affine transformation. 
The residual errors after adjustment mainly involve: The errors of tapping-off 
in the Coordinatograph, the various errors appearing on the negatives, the effects of 
fitting errors of the Orthoprojector (except those portions which were eliminated by 
affine adjustment), errors caused by the system of the directly coupled Orthoprojector 
and appearing because we neglect the slope of the terrain perpendicular to the direction 
of the profile within the profile strips, the effects of errors in planimetry of altimetric 
setting caused by the operator in profile scanning, and finally the errors of the film 
(Agfa Repro half-tone film B/blue) used for map preparation and which appeared after 
its exposure in the Orthoprojector until the tapping-off of the coordinates.