COMMENTS ON THE RENFREW SMALL-SCALE 
MAPPING EXPERIMENT 
by PROFESSOR RICHARD FINSTERWALDER 
Munich 
The President of Commission IV-3 has invited me to make a few comments on the 
small-scale mapping experiment on the Renfrew test area. As a participant in this 
Second International Experiment I would like to say that the material prepared, which 
consisted mainly of a wide-angle stereopair of good image quality, was excellent. The 
landscape of the test area is quite interesting and will be discussed later. The given 
control points as well as the check points to be measured were very well defined. 
With the help of the specifications and the forms supplied, all participants were able 
to proceed in a uniform and clearly-defined manner. This was a great improvement 
on the pioneer experiment, Vercors 2 (First International Mapping Experiment), which 
left too much freedom to the participants. The results of investigations into lens 
distortion and stability of plotters made during that experiment have of course been 
taken into account in this test. Very clear and useful grid tests were included in the 
experimental program. At 1:25,000 the required contour interval was only 5 meters, 
which is a little too small. For clearer graphical presentation it would have been better 
to ask for the final plots in ink, not in pencil, even if additional drafting in ink took 
much more time. 
The participants performed the plotting on first- or second-order instruments and 
submitted the results of grid and spot elevation measurements. After a relatively short 
time they were informed of the results of their test plotting as to completeness of plot — 
linear and other detail — and the mean square error and maximum error of recorded 
elevations. 
For my topographical analysis, I was provided with (1) contour lines in a small 
area with very detailed landforms, (2) a single contour line in very flat terrain, and 
(3) a control profile. 
The invitation to all participants to take part in the final study of the results and 
to cooperate in the final phase of the experiments was very valuable and it is hoped 
that many of the participants have accepted this invitation. For my part, I would like 
to submit the following suggestions for an additional test of the Renfrew area and for 
another small-scale experiment in the future. 
STEREOPAIR FROM Lower Heicur 
The analysis of contouring was intended to be done by detailed analysis of three 
small sections of the plot. These areas, however, are probably too small to allow 
sufficiently reliable conclusions to be drawn, and yet field surveying of larger areas 
would have been too expensive and time-consuming. Instead, photographs from a 
lower altitude, perhaps 2000 m, could be used. Contouring from these larger-scale 
photographs would produce results with a mean square error about one-third that of 
contouring from photographs at 7000 m, and as a result, the weight of low altitude 
contours would be increased 10 times. It could then be assumed that the new contours 
were sufficiently exact to be used in checking high altitude plots. This check could 
be performed by each participant individually. It would be of great value and interest 
if one of the participants could discuss the method and results of the comparison in an 
article, as the author of this article has done with the results of the first mapping test.* 
  
*Finsterwalder, R. “Schichtlinienprufung Vercors 2.” Zeitschrift für Vermessungswesen, Vol. 82, No. 10 
‘October 1957), pp. 329-337; No. 11 (November 1957), pp. 390-395. 
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