On the Stochasticity of Alignment-Functions for Automated Track Maintenance Machines

des Instituts für Geodäsie

Heft 7/1982

On the Stochasticity of Alignment-Functions
for Automated Track Maintenance Machines

Herman QUEE
Utrecht, The Netherlands


In: BORRE, Kai / WELSCH, Walter M. (Eds.) [1982]:
International Federation of Surveyors - FIG -
Proceedings Survey Control Networks
Meeting of Study Group 5B, 7th-9th July, 1982, Aalborg University Centre, Denmark

Schriftenreihe Wissenschaftlicher Studiengang Vermessungswesen, Hochschule der Bundeswehr München, Heft 7, Neubiberg, S. 339-353.



The maintenance of railwaytracks is periodically carried out by hydraulic tamping machines (main tracks in the Netherlands about 1-2 times per years). Modern tamping machines are since 1975 equipped with a servo-guided laser-scanner for use in straight tracks. The Netherlands Railways have introduced a system by which the method of laser-guided tamping can also be applied in curves (circles and clothoides).

The surveying department established in each curve a local co-ordinate system in which th co-ordinates of constraint points in the track and reference points for the laserbeam are determined. Then the ideal alignment for the tracks is designed, consisting of straight lines, clothoides and circles. From these functions setting-out-distances for the laserbeam and guiding data for the tamping machine are computed and via cassettetapes transferred to a microprocessor on board the machine.

All quantities mentioned are derived from stochastic co-ordinates in a local system; this applies also to the alignment functions! The internal system of the tamping machine requires a certain relative precision, whereas the constraints in the tracks (fixed points on bridges, road-crossings, switches etc.) require a certain reliability of these derived quantities.

It will be proved that the stochasticity of a point on the alignment elements (circles etc.), formulated according to BAARDA's theory of S-transformations, is identical to the stochasticity of a network point at the same place. This means that precision and reliability of short distances and angles are invariant (independent from the choice of "base points" for the network-adjustment).

Angles and short distances are the variables on which the above-mentioned requirements for precision and reliability are based, which means that also the requirements are invariant.

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