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against any further practical application of analytical triangulation in 
mapping for almost twenty years. 
Otto von Gruber (1884-1942), a professor and scientific col 
laborator of Carl Pulfrich became famous for his landmark publication 
Single and Double Point Resection in Space” (1924). His lectures in the 
Vacation Courses on Photogrammetry at Jena, first published in 1930 (with 
English reprints published in 1942) provided pioneering theoretical con 
cept, s (von Gruber 1942) on differential formulas of projective relations 
between planes. It was von Gruber who observed in strip triangulation the 
influence of errors in <p on scale and on height. Based on experiments at 
his initiative, two important facts were emphasized, viz., the usefulness 
of auxiliary data and instruments in order to avoid propagation of sys 
tematic errors in strip triangulation and the practical advantage of 
using wide-angle cameras. 
Heinrich Wild (1877-1951) presented in 1926 at the Second Interna 
tional Congress at Berlin his modified plotter prototype known as Police 
Autograph. Subsequently he founded a factory in Switzerland (Wild 
Heerbrugg Ltd.) where hundreds of well-known and w T idelv used opto-mechan- 
ical autographs. comparators and (now) analytical plotters have been de 
veloped and manufactured. 
The Kern Co. (now in the Wild-Leitz group) of Aarau, Switzerland 
joined the photogrammetric industry in 1930 and continued its contribution 
up to this date. Umberto Nistri (1895-1962) of Rome, Italy and Ermeneguildo 
Santoni (1896-1970) of Florence, Italy also contributed essentially in 
designing and manufacturing instruments of various kinds as also in devel 
oping numerous corresponding mathematical concepts. Nistri patented in 
1919 a method of spatial aerotriangulation. This method, however, was 
practically applied for the first time to the use of the Multiplex 
equipment around 1932-33. Georges Poivilliers (1892-1967) of France, 
Edgar H. Thompson (1910-1976) of the UK are credited with numerous analyti 
cal contributions and with designing instruments and stereo-comparators. 
Thompson's finest contributions were in analytical (matrix algebra) devel 
opments, reseau techniques and aerotri-angulation by the method of 
independent models. Thompson edited the British journal "The Photogram 
metric Record" for 14 years. Martin Hotine (1898-1968) of the UK War 
Office, although primarily a geodetist, published two landmark articles on 
photogrammetry concepts, "Stereoscopic Examination of Air Photographs" 
(1927) and "Calibration of Surveying Cameras" (1929). 
Willem Schermerhorn (1894-1977) of The Netherlands who became a 
professor at Delft in 1926, began systematic tests of aerotriangulation in 
1932 and applied these ideas to uncharted lands in the East Indies. In 
close cooperation with Otto von Gruber he contributed much to the under 
standing of error sources and error propagations in phototriangulation. He 
was also the initiator of the ISP journal "Photogrammetria". A post World 
War II Prime Minister of The Netherlands, he was also the founder (in 
1950) of the International Training Center (ITC) for Aerial Survey at 
Delft (now located at Enschede; Schermerhorn 1964). His life was dedi 
cated to the promotion of photogrammetry.