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Report on the work hitherto archieved by Commission C of 
the O.E.E.P.E. 
by G. LEHMANN, Hannover. 
The Commission C of the OEEPE has been charged with an “Experimental study 
of the application of photogrammetry for large-scale mapping, particularly for cadastral 
purposes”. This task includes the treatment of a lot of detailed questions which must 
partly be solved in different ways according to the special kind and character of the 
cadastral systems existing in the different member countries of the OEEPE. Therefore 
it seemed to be as useful as reasonable to study, during the first period of work, the 
problem of how the photogrammetric plotting accuracy depends upon the scale of the 
photograph and thereby to investigate experimentally a problem which is, in any case, 
of utmost practical importance for the application and economy of photogrammetry. 
Following a draft programme of the Stearing Committee the Commission C at its meeting 
held at Delft on April 8 and April 9, 1954 agreed upon the following items to be its 
first aims: 
1. To determine the mean square errors in x, y and z of signalized and non-signalized 
points as well as for any ground lines with respect to different photoscales, and to 
determine the smallest photoscale possible satisfying certain prescribed accuracy 
requirements of the final product, i.e. respectively the transformed machine-coor- 
dinates and the map. 
2. To investigate the accuracy of distances computed by help of the transformed 
machine-coordinates or taken from the map for different lengths and with respect to 
the photoscales. 
oo 
To study the influence of the limits of models, i.e. to compare the coordinates of iden- 
tical points determined in different models and determine the differences in accuracy 
obtained in distances determined when the extremities of the lines are located in one 
model or in two adjacent models. 
4. To investigate the plotting accuracy with respect to the various factors influencing it, 
namely: 
a. the angular field of the camera (normal-angle or wide-angle lens camera), 
b. the photographic material (film or plate), 
c. the method of signalizing points, 
d. the observer, 
e. the type of plotting instrument, if the most suitable scale of the apparatus con- 
cerned is selected as machine scale in accordance with the experiences obtained in 
the Centre, 
f. the base adjustment (internal or external base), and 
g. the ratio of the machine scale to the drafting scale. 
5. To try to analyse the total errors aiming at a determination of error portions due to 
the photograph, the observer, the instrument, the mechanical transport from the 
instrument to the plotting-table, etc. 
For execution of these operations Switzerland offered an experimental area of flat 
and open character situated in the Rhine valley near Oberriet. Covered by airphotographs 
in the summer of 1953 under various photographie conditions, this area corresponded in 
an excellent way to the above outlined aims of research. The Commission C resolved 
therefore to take this test area as a base for the first phase of work. Being 1,5 X 1,5 kilo- 
meters in size this area contains about 600 bound-stones (monuments), the coordinates 
and elevations of which had been determined with great accuracy by terrestrial measure- 
ments. Moreover most of the distances less than 30 m in length were measured directly