G VI1-48 
PHOTOGRAMMETRIC ENGINEERING 
plex model scale and transferred to transparent sheets which are passed to 
the Multiplex operator. In certain cases, for example in a survey of the Zambesi 
region, specialist interpreters produce a separate vegetation trace which is 
similarly scaled for use by the plotters. There seems to be general agreement 
that such a system of pre-interpretation has definite advantages but many 
people doubt whether the separate process is necessary in all cases. It has been 
suggested, however, that the marked-up photographs have an additional value 
when carrying out ground checks. 
At large scales, interpretation in England is universally incorporated in 
the plotting process. The availability of high quality photography referred to 
above has greatly facilitated detailed interpretation on plotting machines pro 
viding a considerable degree of magnification. Until comparatively recently 
almost all of this work was carried out on first-order machines, such as the 
Zeiss Stereoplanigraph or the Wild Stereoautograph, but in addition one con 
cern is now using Kelsh plotters on large-scale work and the development of 
the Williamson LSP machine, also capable of working at large scale on the 
anaglyphic projection principle, should be noted (Photogrammetric Record, 
April 1954). 
In Pakistan, where since the creation of the state, great emphasis has been 
placed on photogrammetrically mapping the entire country, the impetus is now 
shifting to large-scale, special-purpose maps. Photography is interpreted to de 
rive information on geology, soils, and vegetative cover for inclusion on these 
maps. Photography used are mapping verticals, varying from 1:25,000 to 
1:40,000. 
In the Ganges Kobadak irrigation project in East Bengal (Pakistan), some 
3,200 square miles was mapped from vertical photographs (1:40,000 scale); 
simple photographic interpretation techniques were employed to set stone 
position markers for the project. Theoretical positions for the stones were first 
transferred from the maps to photographs, then the photographic detail was 
used to establish the monuments on the ground by check of surrounding ground 
detail. 
Road, Railway and Highway Engineering 
GENERAL APPLICATIONS 
In this, as in other fields of engineering, the use of photogrammetrically pre 
pared maps has been known for some time. The full application of photographic 
interpretation techniques has been somewhat slower in being realized. During 
the past four years, however, the use of photography in this latter way has been 
increasing. 
In Norway, the Road Department uses aerial photography not only for 
mapping transportation routes, but for studying geologic and soil characteristics 
along proposed routes, for locating tunnel sites, for predicting landslide areas, 
and for locating gravel pits for road construction. Quite recently, photography 
has also been used in Norway for making traffic counts. 
Much of the road planning in Sweden is also done from aerial photographs. 
The preliminary location, or “staking out” of roads on stereo models is now 
quite generally practiced, both at the Central Administration and at the local 
sections. Processing then takes place in less complicated stereo-instruments, 
such as mirror stereoscopes, in order to establish the line on which detailed 
staking with ground survey methods will take place. In a few cases this process 
ing is done using precision stereo-instruments. Photographic interpretation 
techniques are used in this planning process to determine the characteristics