They have been developed for results obtained from the EM 120 type geometry cars, operated by diagnostic cetres of Polish State Railways and

The system consists of two main modules - the car real-time measurement module and the stationary data storage module. The measurement module is designed to work in the on-line (real-time) mode when driving along the track, and in the off-line mode during calibration, simulation, and replay of stored results obtained in previous measurement. The user-friendly menu-controlled measurement module software has been developed on a QNX platform. The computer system of the geometry car is designed for measurement and storing the track geometrical parameters according to the customer-specific specifications. It can measure the track in both directions with speeds of up to 120 km/h.

The measured parameters include:

• vertical irregularities of rails - vertical deviation of the rail from the straight reference line, i.e., chord between the contact points of the external wheels with the rail. In practice, the line which is used is determined by two wheels at a distance equal to the measurement base length, i.e., 11.8 m,
• twist - difference of cants over the measurement base length equal to 2.5, 6 or 10 m,
• track gauge - distance between the internal rail head surfaces, measured 14 mm below their crown surfaces,
• cant - defined as a difference between the rails in a vertical plane in a single transverse track section,
• horizontal irregularities of the track (left and right versines), which are defined as the track versine in the horizontal plane, measured with the 10 m long base length, determined for each rail separately.

The car measurement system carries out the following tasks:

• interfaces its computer system with the vehicle's sensors through the specialised I/O cards
• calculates the distance travelled (mileage) basing on interrupts from the programmable divider of the odometer impulses
• measurement data acquisition
• generating the measurement data records synchronised with interrupts from the divider of the odometer impulses
• calculating the primary geometrical parameters basing on the car sensors' readings
• calculating the secondary geometrical parameters
• analysis of defects, generating the statistical and parametrical data
• printout of plots and textual reports on the graphical and character printers
• controlling write and read operations of data to and from the measurement data and configuration files

The track geometry measurement module is fitted with the electro-mechanical measuring equipment controlled by the heavy duty industrial design PC on-board computer system. Moreover, the hardware employed includes the add-on data acquisition boards, one character printer, and a plot mode high-speed heavy duty matrix printer. The operator runs the module and supervises its functioning using one of the terminals installed at the front and rear ends of the car. The auxiliary custom consoles simplify his task of recording additional information about structures like bridges, station platforms, crossovers, semaphores, etc

Thorough analysis of the track geometry parameters is carried out in real-time. Treshold analysis of parameters is also carried out consisting in detection of exceedings of the allowable tolerance limits. Its results are used for generation of the detailed reports on particular defects and reports with the synthetic coefficients of the track condition. Parametric coefficients are always calculated for the user selectable length of the base track sections from the range of 10 m to 1000 m. The accuracy of graphical printouts is better than 0.5% for the longitudinal scale whereas the absolute error of representation of the printed parameters does not exceed 0.2mm.

The stationary data storage module makes it possible to analyse the stored measurement data for different sets of the tolerance limits and can produces graphical plots and textual reports. The important features of this system are:

• reviewing the plots from various measurements with the capability of overlaying them on screen
• maintains the archive of the allowable tolerances' sets, that can be used as standard templates for evaluation of measurement data both on the car and by the stationary system
• has the extensive file management functions for transferring and archiving the measurement data files.