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In young countries with rapid development a cadastral survey is often needed 
within the shortest possible time. The former conventional surveying methods are not 
applicable, since they require a considerable amount of time and personnel. But ex 
perience has proved that a differentially rectified orthophotogram constitutes a good 
and sufficient substitute. This procedure proves especially valuable if boundaries are 
identifiable from the air, as fences and hedges, or if boundary stones were destroyed 
because of certain prejudices of the people concerned. That such a photo “map“ is of 
considerable and sufficient accuracy, has been proved by Neubauer by means of a 
test area in the Suabian Alb (slopes up to 30%). His study is published hereinafter. 
A carefully executed comparison with points which had been trigonometrically deter 
mined has resulted in an accuracy of 
± 0.12 mm 
which refers to the scale of the orthophotogram and which is expressed as mean square 
coordinate error. 
An additional tracing of boundaries by means of white ink will increase the 
legibility of the plan. The abundance of information shown on the terrain (as trees, 
stone marks etc.) facilitates the revision. It may be supposed that this procedure will 
gain many friends and imitators. It will be applied in practice for the first time in 
Central America and probably also in Thailand. 
Another field of application is given in practical geology. The differentially 
rectified map is an ideal auxiliary means for the work of the interpreting geologist, 
as all places of geological interest in nature can exactly be taken from the map. 
These fundamental thoughts led to the creation of the Orthoprojector. I feel 
indebted to Russel Bean for his information about the types of orthophotoscopes he 
has developed. These instruments inspired and incited me to pursue such a develop 
ment independently.