EP1418273B1 - Method of tamping railway tracks - Google Patents

Abstract

The ballast vehicle is driven along the working railway line, and its outlets are computer controlled to deliver ballast to the track. A series of measuring gauges (7.1 - 7.n) which are capable of tracking a target (P1, P2) situated on the ballast vehicle, and continuously calculating position and transmitting this information to a processor mounted on the ballast vehicle. This is linked to the computer system. The procedure for carrying out works on railway lines includes filling the line with ballast. The ballast vehicle is driven along the line requiring work, and its outlets are controlled by a computerized system which compares a theoretical model of the line with the real topographical data derived from the line under maintenance. This includes the use of a series of measuring gauges (7.1 - 7.n) which are capable of tracking a target (P1, P2) situated on the ballast vehicle, and continuously calculating the topographical position of the target, and continuously transmitting this information to a processor mounted on the ballast vehicle. This is interfaced with the computer system which controls the output of ballast. The targets (P1, P2) may consist of front and rear prisms, co-operating successively with at least three automatic theodolite stations situated along the length of the track to measure the advance of the vehicle.

Description

The invention relates to railway works and more particularly to ballast treatment operations by means of machines commonly known as tampers-graders (mechanical stuffing).

Theoretical description of these lane maintenance operations is given in the reference book LA VOIE FERREE, Jean ALIAS, EYROLLES PARIS 1984.

Furthermore, it is known from patent EP 0 293 015 a control device of a leveling and skimming machine a railroad track in which receivers carried by the machine control the work to be performed from data defining the state of the way. Said data are determined by the examination of portions of illuminated by two laser beams emitted by a transmitter system installed on a trolley parked on the way.

The present invention aims to meet the new constraints imposed railway undertakings by track operators during stuffing called "strict absolute basis".

• la machine doit avoir un rendement d'environ 900 m/h ;
• aucune intervention extérieure ne doit avoir pour conséquence de faire pénétrer des personnels et/ou des engins dans la portion de voie en cours de traitement par la machine, ni sur la voie contiguë circulée ;
• les valeurs typiques de la voie doivent être maintenues en base absolue stricte tous les dix mètres avec référence aux poteaux qui supportent la caténaire ;
• avoir dans la même passe de travail un relevé numérique des travaux réalisés ;
• vérifier en temps réel que la machine ne dérive pas entre deux repères caténaires.

These constraints are mainly the following:

• the machine must have a yield of about 900 m / h;
• no external intervention shall result in the entry of personnel and / or machinery into the portion of the track being treated by the machinery, nor on the contiguous track circulated;
• the typical values of the track must be maintained in strict absolute base every ten meters with reference to the posts supporting the catenary;
• have in the same workflow a digital record of the work done;
• check in real time that the machine does not drift between two catenary pins.

To achieve these results, the invention proposes a method based on the use of a battery of measuring devices capable of tracking a target moving by instantly calculating its topographic position and transmitting to a station for calculating digitized signals characteristic of this topographic position, this battery of devices forming a chain running like a noria as and when measuring the movement of the tamper on the track being serviced.

Taking topographic references along three XYZ axes using Laser theodolites pointing a target is well known to surveyors. It exists the market for stations of this type equipped with motorized means of orientation and equipped with radio transceivers to transmit digitally the data measured at the theodolite to a unit of calculation.

These stations are equipped with means to remotely control them remote.

In addition, they are able to track a moving target and continuously measure the topographic positions of this target. Such a station is by example marketed by the German company LEICA under the name commercial TCA 1800.

According to the invention there is proposed a railway tamping method in a tamping machine is driven on the working track and its stuffing members are ordered from a computerized system comparing a theoretical model of the track with the actual topographic data of the way to work characterized in that it comprises the use of a measuring apparatus noria, said apparatuses being arranged along the track close to it and capable of tracking two targets placed on the tamper by continuously calculating the topographic position said targets and to continuously transmit these topographic positions to a unit of embedded calculation on the tamper and interfaced with the computerized system of control of stuffing bodies.

• la bourreuse est équipée d'un prisme avant et d'un prisme arrière coopérant successivement avec au moins trois desdits appareils de mesure, respectivement constitués par une station théodolite automatisée, déplacées le long de la voie au fur et à mesure de l'avancement de la bourreuse,
• les apparareils de mesure sont placés sur les poteaux caténaires de la piste bordant la voie à entretenir selon un pas de trois et sur les poteaux caténaires intermédiaires sont disposés des prismes nécessaires à l'acquisition par chaque station théodolite de sa position topographique de référence,
• les prismes des poteaux caténaires sont déplacés le long de la voie en même temps que les stations théodolites,
• le procédé met en oeuvre trois stations théodolites combinées avec six prismes d'acquisition de la position topographique de référence desdites stations.
• le procédé met en oeuvre six stations théodolites,
• le procédé met en oeuvre une combinaison de six stations théodolites et de douze prismes disposés sur les poteaux caténaires,

The process according to the invention is still remarkable for the following preferred characteristics:

• the tamper is equipped with a front prism and a rear prism successively cooperating with at least three of said measuring devices, respectively constituted by an automated theodolite station, moved along the track as and when advancing the tamper,
• the measuring apparatus are placed on the catenary posts of the track bordering the track to be maintained in a step of three and on the intermediate catenary poles are arranged prisms necessary for the acquisition by each theodolite station of its reference topographic position,
• the prisms of the catenary poles are moved along the track at the same time as the theodolite stations,
• the method uses three theodolite stations combined with six prisms for acquiring the reference topographic position of said stations.
• the process uses six theodolite stations,
• the process uses a combination of six theodolite stations and twelve prisms arranged on the catenary poles,

• le chantier est divisé en tronçons unitaires correspondant à un intervalle de trois poteaux caténaires, deux poteaux adjacents portant un prisme de référence et de mesure topographique et le troisième poteau portant une console amovible pour supporter une station théodolite automatisée,
• il est disposé sur les poteaux caténaires le long de la voie à travailler, six stations théodolites dans six tronçons unitaires contigus de telle sorte que chaque station soit séparée de ses voisines par deux poteaux caténaires portant chacun un prisme de référence,
• il est disposé sur la bourreuse deux prismes de référence et de mesure, l'un à l'avant, l'autre à l'arrière,
• avant l'arrivée de la bourreuse sur le chantier, les stations théodolites exécutent une procédure d'acquisition de leur position topographique de référence à l'aide des prismes disposés sur les poteaux caténaires intermédiaires puis sont mis en attente de l'arrivée de la bourreuse sur la voie à travailler,
• à l'entrée de la bourreuse (1) sur la voie à travailler un opérateur embarqué commande le calage de la première station théodolite sur le prisme arrière porté par la bourreuse et le calage de la deuxième station théodolite sur le prisme avant,
• les deux premières stations théodolites transmettent en continu les valeurs des coordonnées topographiques des prismes arrière et avant aux moyens de calcul embarqués sur la bourreuse, lesdits moyens de calcul produisent les coordonnées topographiques réelles de la voie et les adressent par une interface au système de bourrage assisté par ordinateur de la bourreuse,
• ces coordonnées sont comparées avec le modèle théorique de la voie préenregistré dans le système de bourrage assisté par ordinateur et les organes de bourrage de la bourreuse sont commandés en fonction de la différence entre ce modèle théorique et la position topographique réelle de la voie définie à partir des mesures des stations théodolites actives,
• les stations théodolites actives poursuivent les prismes arrière et avant jusqu'à l'approche de la fin du premier tronçon unitaire du chantier,
• l'opérateur embarqué commande alors le calage de la station théodolite suivante sur le prisme avant tout en maintenant le calage de la station théodolite précédente sur le même prisme avant,
• à l'arrivée de la bourreuse au droit du poteau caténaire portant la station théodolite précédente, l'opérateur embarqué commande le calage de ladite station théodolite sur le prisme arrière et désactive la première station théodolite,
• la première station théodolite est transportée et réinstallée sur un poteau caténaire en avant de la dernière station théodolite du tronçon unitaire en cours de travail, où elle est mise en attente après ré-acquisition de sa nouvelle position topographique de référence à l'aide des prismes portés par les poteaux caténaires adjacents,
• les étapes ci-dessus d'activation et de déplacement des stations théodolites se reproduisent continûment jusqu'à la fin du chantier au fur et à mesure de la progression de la bourreuse.

The railway tamping method according to the invention advantageously implements the following operations:

• the site is divided into unitary sections corresponding to an interval of three catenary poles, two adjacent posts carrying a reference prism and topographic measurement and the third post carrying a removable console to support an automated theodolite station,
• it is arranged on the catenary poles along the way to work, six theodolite stations in six contiguous unitary sections so that each station is separated from its neighbors by two catenary posts each carrying a reference prism,
• two reference and measuring prisms are arranged on the tamper, one at the front and the other at the rear,
• before the arrival of the tamper on the construction site, the theodolite stations perform a procedure of acquisition of their reference topographical position using the prisms arranged on the intermediate catenary poles then are put on hold of the arrival of the tamper on the way to work,
• at the entry of the tamper (1) on the working track an on-board operator controls the setting of the first theodolite station on the rear prism carried by the tamper and the setting of the second theodolite station on the front prism,
• the first two theodolite stations continuously transmit the values of the topographic coordinates of the front and back prisms to the calculation means on board the tamper, said calculation means produce the actual topographic coordinates of the track and address them by an interface to the assisted stuffing system by the computer of the tamper,
• these coordinates are compared with the theoretical model of the pre-recorded lane in the computer-assisted tamping system and the tamping devices of the tamper are controlled according to the difference between this theoretical model and the actual topographic position of the lane defined from measurements of active theodolite stations,
• the active theodolite stations continue the prisms behind and before until the approach of the end of the first unitary section of the site,
• the onboard operator then controls the setting of the next theodolite station on the prism before maintaining the setting of the previous theodolite station on the same prism before,
• at the arrival of the tamper at the catenary post bearing the previous theodolite station, the onboard operator controls the setting of said theodolite station on the rear prism and deactivates the first theodolite station,
• the first theodolite station is transported and reinstalled on a catenary pole in front of the last theodolite station of the unitary section during work, where it is put on hold after re-acquisition of its new reference topographic position using the prisms carried by adjacent catenary poles,
• the above steps of activation and relocation of the theodolite stations recur continuously until the end of the work site as the tamper progresses.

• lors du déplacement d'un station théodolite vers sa nouvelle position d'attente, les prismes disposés en arrière de la station considérée sont également déplacés et reposés sur les poteaux caténaires précédant celui où est réinstallée la station considérée,
• sur leurs poteaux caténaires respectifs, les stations théodolites sont déportées en direction de la voie, par rapport à la file de poteaux caténaires, d'une distance suffisante pour leur permettre de viser les prismes sur les poteaux caténaires adjacents avec une distance angulaire suffisante lors de la routine d'acquisition de leur nouvelle position topographique de référence.
• le déport de position d'une station théodolite par rapport au poteau caténaire qui le porte est de l'ordre de 30 à 35 cm tandis que le déport des prismes par rapport aux poteaux adjacents est de l'ordre de 6 cm.

In a variant, this process has the following advantageous characteristics:

• when moving a theodolite station to its new standby position, the prisms placed behind the station in question are also moved and rested on the catenary poles preceding the one where the station in question is reinstalled,
• on their respective catenary poles, the theodolite stations are deported towards the track, with respect to the line of catenary poles, of a sufficient distance to enable them to aim the prisms on the adjacent catenary poles with a sufficient angular distance during the acquisition routine of their new reference topographic position.
• the positional offset of a theodolite station relative to the catenary pole which carries it is of the order of 30 to 35 cm while the offset of the prisms relative to the adjacent posts is of the order of 6 cm.

The invention allows the realization in a single phase of the finished work compared to the theoretical project, indeed the system positions the channel in XYZ coordinates with a continuous acquisition of the correction values according to a step which can range from 10 cm to 150 m and which in practice will most often be fixed at 10 m. Thus, the defects of small or large wavelength can be corrected instantly and simultaneous recording of the work carried out allows control and guidance of the tamper in real time.

The stations are taken over as soon as the tamping machine arrives on the site, it becomes immediately operational, the pre-registration phase the track is deleted.

• La figure 1, est un schéma représentant symboliquement une bourreuse équipée d'un prisme avant et d'un prisme arrière.
• La figure 2, est une représentation symbolique d'un tronçon N de trois poteaux caténaires dont l'un porte une station théodolite et les deux autres portent un prisme.
• La figure 3, est une représentation symbolique de la disposition de trois stations successives sur les poteaux caténaires longeant une voie ferrée.
• La figure 4, illustre symboliquement l'arrivée de la bourreuse sur le chantier.
• La figure 5, illustre symboliquement une bourreuse en cours de travail entre deux stations.
• Les figures 6, 7 et 8 illustrent la poursuite du travail lors du passage d'un premier groupe de stations au groupe suivant.

Other features and advantages of the invention will emerge from the following description of a nonlimiting exemplary embodiment with reference to the appended diagrammatic drawings in which:

• Figure 1 is a diagram symbolically representing a tamper equipped with a front prism and a rear prism.
• Figure 2 is a symbolic representation of a section N of three catenary poles, one of which carries a theodolite station and the other two carry a prism.
• Figure 3 is a symbolic representation of the layout of three successive stations on the catenary poles along a railway line.
• Figure 4 illustrates symbolically the arrival of the tamper on the site.
• Figure 5 illustrates symbolically a tamper in the course of work between two stations.
• Figures 6, 7 and 8 illustrate the continuation of the work during the passage of a first group of stations to the next group.

Currently, catenary poles arranged along a railway electrified are spaced a distance of 50 meters. They are all equipped with devices enabling the attachment of various apparatuses at points whose topographical coordinates are known in advance and are part of the data of the theoretical model of the route communicated by the company operating the route to the railway works undertaking responsible for the maintenance operation of the track.

The tamping-leveling machine 1 running on track 2 in the direction of the arrow 3 was equipped with two prisms P1 and P2 reference and measurement capable of intercepting a 360 ° light beam. By convention P1 is the prism arranged at the front of the machine and P2 is the prism arranged at the back of the machine (Figure 1).

These prisms P1 and P2 can be directly mounted on the tamper 1 proper.

Alternatively, the prism P1 mounted on a light self-propelling truck in front of the tamper and equipped with a tilt inclinometer and an inclinometer tilts while the P2 prism can be mounted on an LDR carriage (Reading the Directed Devers) pulled by the tamper in a manner known per se.

In the case where the prisms P1 and P2 are not mounted on the tamper 1 itself but on trolleys accompanying the tamper, these trolleys are equipped with means of adaptation to the tamping machine for their transport on the top-foot (HLP).

The tamper 1 is further equipped with two wave transceivers radio, one R1 dedicated to receiving the values transmitted by the theodolite stations before work, and the other R2 dedicated to receiving the values transmitted by the theodolite stations after work.

• une unité de calcul C1 recevant les données de l'émetteur-récepteur R1 qu'elle compare au projet théorique pour obtenir les valeurs de correction en relevage et en dressage et générer les instructions correspondantes par l'intermédiaire du système de bourrage assisté par ordinateur (BAO) qui commande les organes de travail de la machine,
• une unité de calcul C2 qui reçoit les données de l'émetteur-récepteur R2 qu'il compare au projet théorique pour obtenir si nécessaire les valeurs de correction en relevage et en dressage après le travail (recollement) ;
• une interface dédiée à la transition des valeurs de correction entre l'unité C1 et le système de (BAO) de la bourreuse 1.

It also features computer processing equipment that includes:

• a calculation unit C1 receiving the data from the transceiver R1 which it compares to the theoretical project to obtain the correction values in lifting and training and generate the corresponding instructions via the computer-assisted tamping system ( BAO) which controls the working elements of the machine,
• a calculation unit C2 which receives the data of the transceiver R2 which it compares to the theoretical project to obtain if necessary the correction values in lifting and training after work (recollement);
• an interface dedicated to the transition of the correction values between the unit C1 and the system (BAO) of the tamper 1.

Advantageously, the tamper will also be equipped with a printer for the paper edition of the graphic and numerical listing of the values recorded by calculation units C1 and C2 before and / or after work. She will be able to also include any data storage device working under a pre-established format allowing the subsequent recovery of these data by other software.

Along the track adjoining the track, the catenary posts 4 arranged with a interval of 50 meters will receive, in groups of three, two reference prisms 5 and measurement identical to the prisms P1 and P2 carried by the tamper 1 (prisms 360 °) and a robotic theodolite station 7 including a location system automatic, an automatic target recognition system and a transceiver capable of transmitting in digitized form the signals representative of topographic coordinates calculated by the device and to receive orders from aiming from the on-board control post on the tamper 1. To avoid any risk of interference, each station has a separate frequency. The prisms 5 are installed on fixed supports 6, while stations 7 are placed on removable consoles 8 provisionally fixed to the posts 4 by means quick coupler (Figure 2).

Typically, the stations 7.1, 7.2, 7.3 ..... 7.n are therefore spaced 150 meters from each other and the two intermediate poles 4 carry the prisms 5 (Figure 3). The complete device will ideally include six stations 7.1 to 7.n on a section of track 900 m corresponding to a working time of one hour.

As indicated above, as soon as the path to be treated is intercepted, an operator install prisms 5 and stations 7.1 to 7.n on the catenary poles before the arrival tamping machine 1 at the beginning of the construction site. The six stations 7.1 to 7.n are initialized by an automatic routine during which they acquire the coordinates topographic positions of their position by successive sightings of at least three of the four prisms 5 immediately adjacent to each station. Once this position of reference acquired and stored, the station is put on hold of the tamper 1.

At the arrival of this one, the on-board operator tunes the radio frequencies so that the first station 7.1 is wedged on the rear prism P2 and the second station 7.2 is wedged on the prism before P1 (Figure 4). Once set, each station pursues the P1 and P2 prism with which it is associated throughout the progress of the tamping machine 1 and continuously transmits the topographic coordinates of said prism to the corresponding calculation unit C1 or C2 embarked on the tamper.

These values after their treatment by calculation units C1 and C2 allow the onboard operator to choose the correction step addressed to the BAO system: for example acquisition of a value every 10 centimeters and transmission to BAO system every 10 meters, allowing filtering to avoid inconsistencies in values between two points spaced 10 meters apart.

The combination of a measurement taken from the front of the tamper 1 with a measured at the rear of the latter makes it possible to perform an instantaneous gluing of the work done and immediately correct any drift observed between two catenary poles.

When the tamper arrives near station 7.2, the operator boarded shims the next station 7.3 on the prism before P1 so it gets during this transition phase a superposition of the values issued by the stations 7.2 and 7.3 and therefore a relay control between these stations. In practice this superposition will be implemented approximately 30 meters before the arrival of the tamper at the right of the post 4 which carries the station 7.2 (Figures 5 and 6).

When the tamper 1 has reached the right of the post that carries the station 7.2, the operator stalls the latter on the rear prism P2 and cuts the reception of the station 7.1. The latter is then deactivated by an operator circulating nearby the track and transported by the latter to the front of the chain where it is handed over. waiting after running the acquisition routine of his new position topographic reference.

The cycle is like a noria throughout the length of the yard.

The system allows for continuous support of values (ten taken by second for a forward speed of 900 meters per hour or an acquisition 400 values for 1 output value every 10 meters).

A six-station noria provides great flexibility of use with a relative indifference to breakdowns. Indeed, the operator who is responsible for moving the stations from the back to the front has an average of about 50 minutes to make the 750 meters that separate it from the next position of the station it moves. So in case of failure, from a station a noria to only five or even four stations will not affect system performance. In theory, the minimum number of stations for one noria to work is three. Indeed, given a speed of the tamping machine of the order of 5 m / min, the runway operator still has about 20 minutes to make a displacement of 300 meters. However, with a three-station noria, any operational incident of a station will cause stopping the progress of the site.

The system also provides the benefit of allowing all staff assigned to the yard to stay out of the danger zone for the duration of the building site. In fact, the runway personnel only have to move at the posts catenaries to manage the rotation of stations, it never has to be near immediate of the tamper in work.

Claims (11)

1. Method for tamping a railway track, in which a tamping vehicle is driven on the track to be worked upon and its tamping elements are controlled from a computerised system which compares a theoretical model of the track with the real topographical data of the track to be worked upon, characterised in that it comprises the use of a series of measuring gauges (7.1 to 7.n), said gauges being disposed along the track in proximity to the latter and being capable of tracking two targets (P1, P2) disposed on the tamping vehicle by continuously calculating the topographical position of said targets and continuously transmitting these topographical positions to a processor on board the tamping vehicle and interfaced with the computerised system for controlling the tamping elements.
2. Method according to claim 1, characterised in that it comprises equipping the tamping vehicle (1) with a front prism (P1) and a rear prism (P2) cooperating successively with at least three of said measuring gauges, respectively formed by an automated theodolite station (7.1 to 7.n) moving along the track as the tamping vehicle advances.
3. Method according to claim 2, characterised in that the theodolite stations are placed on the catenary posts (4) of the path bordering the track to be maintained according to a spacing of three, and in that, on the intermediate posts (4), there are disposed prisms (5) which are required for the acquisition by each theodolite station (7.1 to 7.n) of its topographical reference position.
4. Method according to claim 3, characterised in that the acquisition prisms (5) are moved along the track at the same time as the theodolite stations (7.1 to 7.n).
5. Method according to claim 4, characterised in that it uses three theodolite stations (7.1 to 7.n) combined with six prisms (5) for acquisition of the topographical reference position of said stations.
6. Method according to claim 3, characterised in that it uses six theodolite stations (7.1 to 7.n).
7. Method according to claim 6, taken in combination with claim 4, characterised in that it uses a combination of six theodolite stations (7.1 to 7.n) and twelve prisms (5).
8. Method of tamping a railway track according to claim 7, characterised in that it performs the following operations:

   the site is divided into unitary sections corresponding to an interval of three catenary posts (4), two adjacent posts carrying one of said reference and topographical measurement prisms (5) and the third post carrying a removeable console (6) for supporting an automated theodolite station (7),

   there are disposed on the catenary posts (4) along the track to be worked upon (2), six theodolite stations (7.1 to 7.n) in six contiguous unitary sections such that each station (7.1 to 7.n) is separated from its neighbours by two catenary posts (4) each carrying a reference prism (5),

   there are disposed on the tamping vehicle (1) two reference and measurement prisms (P1, P2), one at the front (P1), the other at the rear (P2),

   before the arrival of the tamping vehicle (1) on the site, the theodolite stations (7.1 to 7.n) perform a procedure for acquisition of their topographical reference position by means of acquisition prisms (5) which are disposed on the intermediate catenary posts (4), then are put on stand-by for the arrival of the tamping vehicle (1) on the track to be worked upon,

   when the tamping vehicle (1) enters the track to be worked upon (2), an operator on board controls locking of the first theodolite station (7.1) onto the rear prism (P2) carried by the tamping vehicle (1) and locking of the second theodolite station (7.2) onto the front prism (P1),

   the theodolite stations (7.1, 7.2) continuously transmit the values of the topograhical coordinates of the rear (P2) and front (P1) prisms by computing means on board the tamping vehicle, said computing means produce the real topographical coordinates of the track and address them via an interface to the tamping system assisted by the computer of the tamping vehicle (1),

   these coordinates are compared with the theoretical model of the track, which model was stored in advance in the tamping system assisted by the computer, and the tamping elements of the tamping vehicle (1) are controlled as a function of the difference between this theoretical model and the real topographical position of the track, defined from measurements of the active theodolite stations (7.1, 7.2),

   the active theodolite stations (7.1, 7.2) track the rear (P2) and front (P1) prisms until approaching the end of the first unitary section of the site,

   the operator on board then controls locking of the following theodolite station (7.3) onto the front prism (P1) whilst maintaining locking of the preceding theodolite station (7.2) onto the same front prism (P1),

   when the tamping vehicle arrives at the right of the catenary post carrying the preceding theodolite station (7.2), the operator on board controls locking of said theodolite station onto the rear prism (P2) and deactivates the first theodolite station (7. 1),

   the first theodolite station (7.1) is transported and reinstalled on a catenary post (4) in front of the last theodolite station (7.n) of the unitary section being worked upon, where it is put on standby after reacquisition of its new topographical reference position by means of the acquisition prisms (5) carried by the adjacent catenary posts,

   the above steps of activation and movement of the theodolite stations (7.1 to 7.n) are continuously reproduced up to the end of the site as the tamping vehicle (1) advances.
9. Method according to claim 8, characterised in that, during movement of a theodolite station (7.1 to 7.n) towards its new stand-by position, the acquisition prisms (5) disposed behind the station under consideration are likewise moved and replaced on the catenary posts (4) preceding the one on which the station under consideration is reinstalled.
10. Method according to claim 8 or 9, characterised in that, on their respective catenary posts (4), the theodolite stations (7.1 to 7.n) are offset in the direction of the track (2), relative to the line of catenary posts, by a distance which is sufficient to allow them to be sighted on the acquisition prisms (5) on the adjacent catenary posts (4) with a sufficient angular difference during the procedure of acquiring their new topographical reference position.
11. Method according to claim 10, characterised in that the offset of the position of a theodolite station (7.1 to 7.n) relative to the catenary post (4) which carries it is of the order of 30 to 35 cm whilst the offset of the acquisition prisms (5) relative to the adjacent posts is of the order of 6 cm.

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