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PHOTOGRAMMETRIC MEASUREMENTS 
IN THE PRAGUE METRO 
Jiri Sima 
Research Institute of Geodesy, Prague 
My short contribution has been inspired by the discussion held 
in Commission V on the XIIIth Congress of ISP in Helsinki. 
Its actual topic was: How to accelerate som close-range procedures 
in order to deliver the results for solving some engineering tasks 
as quickly as possible. One way has already been presented there 
- the application of digital on-line system. 
I would like to present another example of how to accelerate 
significantly the delivery of results to the user just by creating 
the optimum organisation for performance of the off-line photo- 
grammetric works. 
Since 1974, close-range photogrammetry is being widely used for 
checking the construction and traffic safety in the Prague subway 
(Metro). The requirement of the investor is, in many cases, to 
Obtain the results of photogrammetric cross-sectioning the tunnels 
and stations not more than 24 hours after taking the photographs. 
The first task is to compare the project with the actual stage of 
tunnel construction and to identify non-permissable deviations in 
the position and height. The crew of six technicians, equipped 
with two UMK cameras on a portable base, takes on average 12 stereo- 
pairs containing 130 cross-sections during one 7 hour's shift. 
Each stereopair represents a 10-meter section of the tunnel and 
11 cross-sections which are measured in analogue instruments (Wild A7 
or Technokart Zeiss Jena) equipped with automatic recording of the 
model coordinates on a punch tape. The main problem, to tie at 
least one targeted point of each cross-section to the uniform 
geodetic network, is solved very simply and efficiently just by 
the installation of 11 targets in a straight line, on a wire. 
The second task is to verify periodically the traffic safety of 
Metro lines in operation and to complete its exact documentation. 
However, it is possible to take the photographs only for a period 
of two hours during the night when the traffic is not running. 
In this short interval a crew of five technicians takes, on the 
average, 15 stereopairs representing 225 meters of the tunnel 
and 45 cross-sections checked in detail. Photographic plates are 
developed the first thing in the morning and immediately evaluated 
by numerical photogrammetry. In the afternoon, the model coordinates 
stored on the punch tape are input to the Hewlett-Packard 9820A 
minicomputer equipped with a plotter. After some minutes graphical 
and numerical results revealing the critical sites are obtained.