Commission IV 
Särtryck ur Svensk Lantmäteritidskrift nr 2 1968. 
Aerial Map Accuracy in Photogrammetry 
European Standard Error contra American c-Factor 
Dr. Percy Tham 
In the international field of photogrammetry a critical position to ten- 
ders for aerial mapping surveys is often difficult due to the lack of an 
international standardization in the quality of the maps. 
Accuracy and economy of aerial mapping are both basically depending 
on the determination of the flight altitude. The map accuracy required 
establishes the flight altitude and a linear function is considered to 
exist between them. But, the flight height corresponds to an area photo- 
graphed. Thus, a change of the flight height will result in a square 
change of the number of photographs. Consequently, a change of the 
flight altitude will approximately correspond to a square change of the 
economy of the map plotting. 
Therefore, the determination of the flight altitude is a fundamental 
question for the planning of every aerial mapping. 
Abstract 
The flight altitude is the fundamental element for every aerial mapp- 
ing survey. The altitude determines the map accuracy and the economy. 
But the accuracy as well as the economy are also dependent on the effici- 
ency of the plotting stereo-instrument to be used in each case. A value 
empirically examined in the manufacturer's laboratory shows the instru- 
ment efficiency and quality on the records at the delivery. 
Considering other factors which influence in the practise but under 
normal conditions the user has to classify the instrument by a modified 
value, i.e. an »instrument constant». Based on the map accuracy required, 
the flight altitude will then be calculated by means of this constant for 
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