one — consisting, from sheer necessity, of very small triangles, especially because 
an accumulation of errors, when using an electronic system, is for the greater part 
avoided. 
CHAPTER V. 
Although photogrammetry, for other purposes than topography, is not often 
applied in the Netherlands, it has during the last four years been employed several 
times. Most of these applications had a more or less experimental or improvised 
character. For their normal routine-work of calibrating guns and shells, the Nether- 
lands Army applies photogrammetry. For the synchronisation of the two cameras 
a special electronic equipment was constructed. A Zeiss stereocomparator is used 
for the restitution. 
As regards the application of photogrammetry to medical science, there 
is not much news to report; only two publications of Dutch origin, not reported 
at the Washington Congress, may be mentioned here (34) and (35). 
The Royal Netherlands Navy developed a method for determining the run- 
way of a landing aircraft from a cine-camera record. An article about this method 
by G. Prast will be published in Photogrammetria. 
Most experiments were carried out by the Delft Geodetic Institute. From 
two of them some maps and photographs are shown at the exhibition: The deter- 
mination of lines of main current and stream speeds in waterbeddings and: determ- 
ination of the trajectory of a big tanker during launching. 
The first determination was carried out by means of the Wild A 4 Autograph 
and the 1.20 m base stereo camera belonging to it. About twenty exposures were made 
on one pair of plates, using fluorescent red paint for the targets to obtain maximal 
contrast with the water. (36) gives a description of the procedure. 
The determination of the trajectory of the tanker was an improvisation, 
because only one photogrammetric camera was available and the synchronisation 
was difficult. Each of the four members of the Geodetic Institute made photographs 
with their private (24 x 36 mm) cameras, carefully noting the moment of exposure. 
With the photogrammetric (18 x 19 cm) camera — though not during the launch- 
ing — photographs were made from the same points. The 24 x 36 mm photographs 
were enlarged to the same scale as those taken with the 18 x 13 camera; a certain 
point on the tanker on each photograph was transferred stereoscopically to the 
corresponding photograph taken with the photogrammetric camera. 
In this photograph, of which the inner and outer orientation was known, the 
coordinates of the transferred points were measured and the directions were plotted 
on a large-scape map. 
The Geodetic Institute also made a research of grindstones. Stereoscopic 
photographs were made in a scale of 4:1 with a Linhof 13 x 18 camera with a 
35 mm lens. With the Wild A7 profiles were plotted on a vertically-exaggerated 
scale. 
For the Netherlands Society of Photogrammetry two lectures were held on 
17