5. Accuracy 
As regards accuracy, an essential feature of the DP-1 Double Projector is that it is provided with 
glass plates below the image plane of the plotting cameras. As a result, even film or thin diapositive 
plates will give about the same accuracy — at least geometrically — as grid plates, since there is no 
“sagging” of the photos in the plotting cameras, which is frequently found to be a problem in similar 
designs. 
Measurements in grid models yielded the following values as referred to the drawing plane (2.5x 
total magnification, mean square coordinate errors): 
Horizontal position: + 0.12 mm Elevation: + 0.15%, of the projection distance. 
Practical experience confirming these figures is contained in [5]. Further results will certainly be- 
come available soon, since several plotting organizations are already using DP-1 Double Projectors. 
In addition, reference is made to the comparative tests performed with instruments of different type 
[8]. 
Abstract 
Due to its easy-to-understand design principle and the rigorous solution used, the DP-1 Double 
Projector may be employed as a new stereoplotter of IIb order for both training purposes and medium 
and small-scale mapping. In addition, it is particularly well suited for map revision in which case the 
plotting table is not used and the entire air-photo model projected directly onto the drawing or map 
to be revised. Although full-size photographs are employed, the useful plotting magnification is about 
2.5x. Empirical orientation converges particularly quickly due to a suitable disposition of the different 
axes. 
References 
[1] ScuzmuPrLUG, T.: Die Verwendung des Skioptikons zur Herstellung von Karten und Plünen aus Photo- 
graphien. Phot. Korr. 1898, pp. 114 ... 121, pp. 235 ... 237. 
[2] Hucznsnorr, R.: Photogrammetrie und Luftbildwesen. Vienna 1930, especially p. 77 et seqq. 
[3] Knawzs, J., in: Theodor Scheimpflug, Festschrift zum 150jáhrigen Bestand des staatlichen Vermessungswesens 
in Osterreich, Special Issue No. 16 of Ost. Z. f. Verm., Vienna 1956, especially p. 31. 
[4] FINSTERWALDER, R.: 50 Jahre Doppelprojektor nach Max Gasser, Bul. 36, pp 48 ... 50, 1968. 
[5] Krauss, G.: Laufendhalten von topographischen Karten. Probleme und Erfahrungen. BuL 35, 225 ... 234, 
1967. 
[6] v. GRuBER, O., and Bunknanpr, R.: Der Aeroprojektor Multiplex als Anschauungs- und Übungsgerät im 
photogrammetrischen Unterricht. BuL 11, 11 ... 21, 1936. 
[7] AxrEnp, M.: Über die Abhängigkeit des w-Überkorrekturfaktors von der Anordnung der Kammerkardane. 
BuL 32, 101 ... 105, 1964. 
[8] Scmwipgrskv, K.: Zur Leistung einfacher Doppelprojektoren. BuL 32, 137 ... 144, 1964. 
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