Geo++® GNBAHN is a system for kinematic track survey. It makes the acquisition of the complete track geometry in a single operational step in real-time possible, i.e. the three-dimensional track co-ordinate, the superelevation as well as the gauge while operating with high precision and high spatial density. Geo++® GNBAHN was developed in co-operation with the German Railway (Deutsche Bahn AG) and is already being used on many lines of the DB AG.

Range of Application

Geo++® GNBAHN is suitable for all tasks that require a precise survey of the track position. This comprises:

  • construction and control during new construction and reconstruction
  • marking out of tracks
  • acquisition of required position and actual position
  • digital track database (GuSDE)

System Components

The track centered and rolling survey system carrier SURVER is the carrier platform for all the hardware components of the system (see Graphic 1). SURVER is optional equipped with a point indicator which allows to approach marked points at the track with millimeter accuracy.


The GNSS-multi-station-RTK real-time system Geo++® GNNET-RTK represents the precise three dimensional co-ordinates using high quality GPS and GLONASS receivers. Geo++® GNNET-RTK includes the Geo++® GNDB database which serves to collect and store large-scale and detailed information about the tracks like discrete points (e.g. main points of curve, switches, etc.) and attributes (e.g. platforms, bridges, etc.).

The software Geo++® GNBAHN serves to collect, control and visualize all the measuring data as well as to carry out technical computations concerning the tracks with a graphical user interface.

Geo++® GNBAHN Concept

The Geo++® GNBAHN Concept is highly precise GPS-survey with Geo++® GNBAHN and Geo++® GNNET-RTK with correction data from a public reference station service (i.e. SAPOS®) or from a local reference station (see Graphic 2).


The coordinates can be produced in user specified coordinate system or datum through coordinate transformations. Combined with optional Geo++® GNTRANS module DB_REF is directly available.

Mode of Operation

Owing to its compact and modular character Geo++® GNBAHN allows a speedy measurement during the normal operation of trains. It is not necessary to close the line.

The performance spectrum of Geo++® GNBAHN allows not only to determine differences in position, elevation and superelevation compared with a known required track position but also to determine an unknown track position. In contrast, it is possible to approach and mark out selected single points like for example main points. The user interface Geo++® GNBAHN serves to control the track survey and mapping-out in real-time. Not only the line but also the determined differences in positions and elevations are visualized by means of a high resolution windowing technique. Geo++® GNBAHN runs on a compact field computer which is firmly connected with the SURVER.

By visualizing the results of the measurement in real-time Geo++® GNBAHN offers to the geodesist manifold possibilities of controlling quality and monitoring the current track survey. By this means subsequent surveying jobs can be avoided efficiently.

Geo++® GNBAHN is equipped with different graphical windows (see Graphic 3) on the main screen, where position, required line, differences in position, elevation, superelevation and preceding measuring tips are represented.


In the line window given required lines of different data formats, which describe the desired track geometry, can be read in. Any part of the required line can be represented by means of zoom and scroll functions. The actual position is shown and constantly updated. Detailed information on setting out data can be fetched by mouse click at any time.

For the purpose of controlling quality the deviations between several measuring trips and determinations of differences in positions can immediately be represented graphically.

If there is no required line available, Geo++® GNBAHN offers the opportunity of routing by way of a three dimensional survey of the actual track geometry while simultaneously representing the line by means of spline functions. The continually incoming track co-ordinates are processed dynamically with corresponding algorithms. The resulting splines always describe the actual position of the track in an optimal way.

Geo++® GNBAHN and EM-SAT

For applications of highest accuracy requirements, the Geo++® GNBAHN has been integrated in the Laser-Long-Line Measurement System EM-SAT of Plasser&Theurer. Running combined in EM-SAT-GNBAHN.

Technical Data Geo++® GNBAHN

Performance features of the Geo++® GNBAHN System Components:


  • integrated point indicator (optional)
  • integrated downward inclination sensor
  • accuracy: superelevation: 1 mm – 2 mm
  • integrated gauge measurement
  • user-specific data connection (GSM/GSMR/RADIO) with GPS reference station
  • alternative online and off-line operation
  • operating by 1-2 persons
  • track survey speed ca. 1-2m/s
  • application during normal operation of trains without closing of line


  • processing of high quality GPS and/or GLONASS single and dual frequency receivers
  • SAPOS compatible
  • processing of correction signals from own reference station (format RTCM++/RTCM-2.1)
  • real-time multi-station solution
  • SQL-database (Geo++® GNDB)
  • transformation of co-ordinates  (optional GNTRANS, DB_REF)
  • accuracy: position 5 mm – 10 mm, elevation 10 mm – 15 mm

Geo++® GNBAHN:

  • user-interface with real-time visualization
  • track geometry by graphical and numeric representation of actual position, differences in position, differences in elevation and superelevation
  • survey of lines if no required line is available by spline calculation and output in spline format
  • input of lines from track marking plans
  • modification of lines with subsequent re-computation
  • representation of several required tracks with selection of actual reference track
  • representation of preceding measuring trips
  • representation of differences in position and in elevation of the complete actual measuring trip
  • representation of differences in position and in elevation of preceding measuring trips
  • selection possibilities of lines, measuring trips, differences in positions and in elevations to be represented
  • large-scale zoom and scroll possibilities of representing any sections and scales even during the measurements
  • plausibility check for all incoming data
  • storage of measured positions and stations in co-ordinate files
  • storage of measured differences in positions, in elevations and superelevations in files
  • creation of protocol file with important information concerning the actual measurement
  • display of information about track geometry, position, differences in position and in elevation

Available data interfaces (input/output):

  • ADELT format of DB AG Essen programs (binär and ASCII)
  • Geo++ format (spline)
  • ASCII files of co-ordinates, differences in positions and in elevations
  • various protocol files

Operating system:

  • Wind
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