PHOTOGRAMMETRIC ENGINEERING 
18 
by coordinates. Conversion of scales. Auto 
matic drafting and interpolation up to 3rd 
degree. 
Numerical output coordinatograph (New)— 
Apparatus for measurement of coordinates of 
points shown on a plan for computation of 
area of lots. 
SWISS FEDERAL RAILWAYS 
Equipment for Measurement of Tunnel 
Profiles. Two phototheodolites are perma 
nently mounted on the front end of a railroad 
car. They take normal photographs of the 
tunnel. Their plotting in an autograph plot 
ter thus furnishes the profile. For details see 
“The New Clearance Recording Car of the 
Swiss Federal Railways” below. 
New Methods 
FEDERAL POLYTECHNIC SCHOOL. ZURICH. 
Professor Dr. H. Kasper. Constant base aerial 
triangulation in the Wild A8 stereoplotter 
and spatial transformation of the coordinates. 
(Publication to appear.) 
POLYTECHNIC SCHOOL OF THE UNIVERSITY 
of lausanne. Prof. Dr. W. K. Bachmann. 
Research on the precision of the numerical 
orientation of any aerial photography in a 
universal stereoplotter. See list of publica 
tions. 
FEDERAL topographic service, bern. Re 
vision of existing maps is done primarily by 
aerial photography. Photos are taken accord 
ing to a flight plan which takes account of 
the configuration of the ground. Longitudi 
nal overlap of 60 to 80 per cent and side over 
lap from 20 to 30 per cent. There is no pre 
liminary marking and the stereoscopic model 
is adjusted by means of existing maps at 
1:10,000 or 1:5,000. For the map at 1:25,000, 
plotting is done directly at the scale of the 
map by engraving or pencil drafting (scrib 
ing). Revision of maps at 1:50,000 and 1: 
100,000 is done by a new drafting of the 1: 
25,000 map treated as mentioned above. For 
several years, plotting of contours at scales of 
1:4,000 to 1:10,000 have been done directly 
by engraving on the base document (original 
draft). Publication of Mr. Lips, Engineer of 
the Federal Topographic Service, “Attempt 
to Convert Photogrammetrically-Obtained 
Contour Lines in Wooded Areas as Base for 
Small Scale Mapping.” (To appear in the 
near future.) 
The New Clearance Recording Car of the 
Swiss Federal Railways (sbb) 
“In ever increasing numbers the Swiss rail 
ways have to transport goods of dimensions ex 
ceeding the standard loading gauge. To a great 
extent, such transport assignment can be 
handled by utilizing the margin between the 
standard loading gauge and standard clearance 
gauge. In many cases, however, it is necessary to 
make use also of the gap that exists between the 
standard clearance gauge and the actual clear 
ance available at given points. 
“Numerous cross sections must be checked to 
judge the feasibility of each excess-dimension 
shipment, but the structure gauge files are quite 
dated and largely of insufficient reliability, neces 
sitating the measuring of many new clearances. 
“At present, each of the SBB Regions has a 
clearance recording car of simple design. These 
cars have proven too inefficient, especially if 
used on the busy trunk lines with their high traf 
fic density and the resulting short intervals be 
tween trains. 
“Looking for new equipment, preferably of a 
kind not requiring physical contact with struc 
tures, photogrammetry appeared as a likely solu 
tion. It should be explained that to this day the 
European railway authorities measure their 
clearances with big pantographs, polar and 
orthogonal coordinate equipment, feeler devices 
mounted on railway cars, and by the so-called 
photographic section method. 
“The principle of the photogrammetric 
method is based on the stereoscopic effect, 
achieved by photographing the same object from 
two different exposure stations. For the subse 
quent restitution process in the office both pic 
tures are viewed in the so-called Autograph, 
where the operator sees a three-dimensional 
image. This spatial viewing permits scanning of 
the ‘model’ with a mobile measuring mark. The 
movements of this measuring mark are trans 
mitted directly to a tracing stylus. In this way, 
total moving dimensions are obtained, in con 
trast to ‘mechanical’ cross sectioning methods 
which supply only a number of individual points 
of each section. Required accuracy and the me 
chanical limits of the Autograph determine the 
limits of the restitution range (maximum cam 
era-object distance); within this range any 
number of cross sections can be plotted. 
“The photographic equipment consists of two 
terrestrial photogrammetric cameras by Wild- 
Heerbrugg. They are mounted on a girder of 
sheet steel which can be levelled; the distance be 
tween the cameras is 2.4 meters. Scale of the pho 
tographs is checked by means of a ‘distance tar 
get’ located about 23 meters (75 ft.) from the 
car aud photographed with every picture. For 
this purpose two small four wheel trucks are pro 
vided, connected to the survey car by two tubu 
lar light metal tow bars. On sidings and during 
transit runs they are stowed underneath the car. 
For the photographs, number plates are used as 
distance targets, simultaneously serving to 
identify the pictures numerically (the truck 
nearer the car merely serves as an intermediate 
tow bar support), illumination at night and in 
tunnels is provided by a 3,000 watt floodlight 
mounted on the girder between the two cameras. 
“The clearance recording car, built in the Yver 
don shops, consists of a rebuilt three-axle coach 
chassis and a new body, lined with specially 
treated hardboard panels of the kind now used in 
the construction of covered freight cars. Either 
end of the car has a roofed platform from which 
the photographs are taken. For immediate 
checks on the quality of the pictures and for re-