The two cameras are equipped with Rolleimatric with re-
seau, they make the photos. The pictures are made usu-
ally on very sensible films. The location of the cameras
was determined partly by direct measurement, partly by
calibration; we shall write about the calibration later. In
order to insure the required illumination from time to
time - we used two flashes of great efficiency. The system
of controlpoints was made by invar bars they were situ-
ated on the platform. It served as the repeated determi-
nation of the elements of orientation marks/ checkpoints.
We started our first experiments in autumn 1990 they
proved that the elaborated system is suitable - under reg-
ulated speed conditions - for making good quality snap-
shots.
4. CALIBRATION OF MEASURING SYSTEM
The calibration of the measuring system means the loca-
tion of the points of minor control and also the location
of the distinctive points. Calibration was made on an
expecially located area of the Hungarian Railways. The
necessary measurements were made by second theodolite
and by invar tapes.
The precision of the cariblation up to present is charac-
terized by the standard deviation of 0.5mm of the co-
ordinates. The comparison (cross-cheking of the results
of calibration made in different times indicates the con-
siderable stability of the points of minor control.
5. THE STEREOPLOTTING
We made some previous analysis concerning the stereo-
plotting and it seemed clear that we needed a working
evaluation system based on analytical principle. The use
of an analytical plotter - this accomplishment seemed ev-
ident - we could not afford. In its lack we suggested the
required transformation of a rather old stereo-comparator
type Zeiss 1818.
After its service, adjustment and (re)calibration this in-
strument was fit with / equipped with an electronic
marker and an impulse-transforming circuit. This made
possible the mensurration of the rotation of the four mea-
suring springs with electronic marks. These marks gener-
ate an independent succession of square-waves. This suc-
cession was fitted with the counter cards of an IBM XT
compatible personel computer throw a shield of buched
cable.
The couter cards are suitable for the registration of the
incoming marks under the influence of the software and
partly under the influence of the pedal. The measuring
system was completed even with a printer and a plotter.
The principle of the struture of the measuring system is
depicted in the figure 2:
printer plotter
system of fits
Zeiss 18 18
=
mark contact
The elaborated measuring system is suitable for the lo-
cation of every single image-point of the co-ordinates of
the instrument to the precision of 0.005mm. In order to
process the pairs of points by means of this measuring
system, the following types of points can be measured:
— reseau points
— prints of minor control
points of the rail serving the location of the clearance
chart
— points of the clearance chart.
6. THE PROGRAM SYSTEM
The evaluation program system is controlled by personal
computer. The system contains five pseudo-systems:
— universal
— measuring
calculation
— drawing
— data transmitter.
The measuring pseudo-system insures the identification,
the storage and the processing of the measured coordi-
nates. The principal task of the pseudo-system is to de-
scribe grphically the situation of the counter card throw
the built-in driving gear of the software and the storage
of the measured points with their scores and coordinates.
The processing og the measured data contains the follow-
ing operations:
— error filtering (based on repeated measuring)
— centralization
— conversion to the calibration coordinate system
— correction of the bad drawing.
The task of the measuring pseudo-system is the determi-
nation of the points of the clearance chart. The two teps
of the calculation are:
— determination of the points of minor control
— transformation of the points of the clearance chart
into the chart.
The first step is equalization of the bundle of rays. The
programme of the equalization of the bundle of rays was
built in the usual way, departing from the collinear equa-
tion.
The calculation was devided into two parts: the simula-
neous resection at the place of perspective center wards
the intersection of the point of the clearance chart. The
task can be solved by the point situated on the platform
of the rail car. Then are the points of minor control.
The second step is the transformation of the points into
the clearance chart. This was made by putting the chosen
measured points of the rail to its proper use, the transfor-
mation was based on spatial similitude. The task of the
drawing pseudo-system is the generalization of the eval-
uted clearance charts drawn by the plotter. The plotter
drawing is an obstacle drawing. This drawing contains
the datum lines of the clearance chart. The sample of
the clearance chart which is valid at a given portion and
the edge of the abstacle. (The plotter draws the points in
such order in which the evaluation was made. Afterwards
it draws the obstacle.)
