rs 
ents 
It does, however, seem to be quite clear that the next step forward 
of the development of the Le ion of the aids to highway and 
railway planning and design will concern the semiautomated technique, 
where the combination of photogramn ietry and field surveying will play 
an important role. 
The practical experiences and the further development of the semiau- 
tomated twodimensional photogrammetric system developed and applied 
by Rijksvaaterstaat in Holland is describ ed by Dr M Tienstra as 
  
  
follows: 
Digital Plotting - Present Situation at the Survey Dept. of the Mi- 
nistry of Transport and Public Works, Delft N.L. 
Outwardly little has changed in the past three or four years. Still 
4 to 5 instruments are currently being used for data collection, check 
plots are being made on a drumplotter and final maps on a Calcomp 745 
flat bed plotter. The data collected during field completion are still 
being processed by hand. This does not mean however, that development 
of the method has come to a standstill. The time has been used to ob- 
tain experience and, above all, to formulate the requirements for the 
next step. 
+ 
The major drawbacks of the present situation are: 
a. checking of data and preparation of a checkplot takes too much 
time. 
b. merging of data from different sources is barely possible. 
C. correction of errors and imperfections is extremely cumbersome. 
The most likely way to improve the procedure was thought to be the 
introduction of an interactive di RD 10 with hard copy provisions. Af- 
ter rather eleborate investigation s a Laser Display HRD-1 was chosen. 
Its great advantage is the very lar rge screen (70 x 100 c.m.) and the 
high quality hard copy it pr "oduces. Its capacity for interaction is 
limited, but is expected to be sufficient for cartographic applications. 
In order not to burden the controller of the Laser Display with rela- 
tively simple checking routines, desk calculator will be used for 
the checking on syntactic errors (numerically detectable errors). The 
system will become operational on an experimental basis in 1976. It 
is expected to become fully productive in 1977. 
so © 
As now also the number of photogrammetric plotters that are being 
used for digital plotting can be increased, quite some thought has 
been given as to the most suitable type of registration equipment. As 
the Department will own before long some 30 plotters, it is worthwhile 
to look into the cost/benefit properties of various types of equipment 
offered. It was found that, when larger numbers are needed, conventio- 
nal registration units with papertape output are so much cheaper than 
any other proposition (microprocessors, deskcalculators, mini's), that 
they are really the only possible choice. It was then decided to buy 
conventional systems and one or two deskcalculators for common use. 
Procedure 
- Pre-plotting editing by marking on paperprint. 
- Photogrammetric restitution with papertape output 
o numerical absolute orientation prior to plotting, 
0 syntactic check on deskcalculator.