Monitoring vehicle positions

Monitoring vehicle positions

Principles of monitoring vehicle positions

Position monitoring units are generally based on receiving satellite signal using GPS modules (global positioning system). Other standards can be used as well, e.g. Galileo for Europe or Glonass (Globalnaja navigacionnaja sputnikovaja sistěma) for Russia.

Principle of determining vehicle positions at the dispatching using GPS

  1. GPS navigation system satellites (or other systems – Galileo or Glonass) placed on medium orbit continually transmit information regarding their position.
  2. The antenna for receiving GPS signal from satellites. This antenna serves only for receiving satellite signal, it does not communicate with the satellites. The antenna can be passive or active. Active means that it has an integrated signal amplifier which improves system sensitivity and ensures more accurate position detection. In this case it requires power supply via a central conductor of a coaxial cable which can be controlled for short circuiting (usually during the installation).
  3. The unit for determining vehicle position. This unit consists of a GPS module and a vehicle communication unit. The GPS module processes signals from the GPS antenna and determines the position of the antenna on the basis of the signals. The communication unit sends this information using a communication protocol and radio signal to a superordinate system for further processing – e.g. to the central dispatching monitoring the vehicle. The communication unit can be included e.g. in our MSP position monitoring module  , on-board computers of the EPIS 4.0x series EPIS 5 FCC on board computers with the check-in function  or other units. To ensure correct vehicle position determination it is necessary to receive signals from at least three satellites, therefore the communication unit has to include “some” radio transmitter (GSM/GPRS/3G … or for private radio networks, e.g. DP networks).
  4. The antenna for communicating via radio networks of mobile phone operators or via DP radio networks. This antenna sends position information via a radio network to the central dispatching.
  5. Radio networks of mobile phone operators or DP networks ensure communication directed from the vehicle to the CED server (Central Dispatching) of a transportation company (DP) or an integrated transportation system (IDS) or generally the dispatching of the transporter, e.g. our  EPIS_FDNET radio network .
  6. The CED Server receives position information from vehicles using a defined communication protocol which sends position information and possibly other information (the speed of the vehicle, azimuth, …) to the dispatching or similar departments. The most frequent tasks of the server are assessing the position of the vehicle in relation to the schedule and communicating other information regarding non-standard traffic occurrences and sending information to station electronic communication panels. This is solved by our dispatching SW SPRINTER which can be supplied in various forms (DP, IDS, …).
  7. The CED dispatcher uses information supplied by the server to solve traffic situations and take necessary measures.
Pic. no.1:The  principle of monitoring vehicle positions.

Pic. no.1:The principle of monitoring vehicle positions.

General properties of GPS modules

The embedded modules of GPS receivers used by our company today work with the newest technology SIRF STAR IV (our products introduced to the market before 2011 use the SIRF STAR III technology). The GPS modules use an advanced technology for suppressing interferences from the antenna, they contain both a digital processor part and an innovated high-frequency architecture. When the receiver is turned on, it quickly finds the correct GPS position according to the type of start. Methods using the SIRF STAR technology are based on correlative calculations.

Receiver frequency: 1575,42 MHz
Received channels: 48 satellites (for SIRF STAR III only 20)
Accuracy: 2,5 m (for SIRF STAR III only 5 m)
Temperature range: -40 to +85 °C (operation, transportation and storage)
Maximal course update: 1 Hz
Used sentences: according to NMAE 0183
Speed accuracy: 0,1 m/s
Module sensitivity: Better than -163 dBm (for SIRF STAR III than -155 dBm )

Ways of monitoring vehicle positions

We offer 3 different ways in the scope of devices and systems supplied by our company:

On-board computer with the position monitoring function

The on-board computers supplied by our company (on-board computers of the EPIS 4.0x seriesEPIS 5 FCC on board computers with the check-in function)  are equipped with vehicle position monitoring GPS modules. These on-board computers use the acquired GPS position not only for position monitoring by the dispatching but also for automatic vehicle orientation on the route for the purposes of the following functions:

  • assessing stop position for automatic stop announcements,
  • solving vehicle preference at crossroads,
  • directing information on passenger LCD displays,
  • etc….

Units for position monitoring using GSM/GPRS/3G networks – the MSP type

Vehicle position monitoring modules – MSP -  are made for vehicle position monitoring by the dispatching in the scope of IDS JMK. However, their use can be more general than just the scope of IDS JMK. If the protocols are modified they can be used in a completely  general way. Now they use GPRS radio transmissions for data transfers and they also use GSM for voice communication. They can work in networks of all cell phone operators.

  • MSP 1.1. – basic version for voice and data communication with the dispatching
  • MSP 3D – basic version extended by a single-channel digital stop annunciator
  • MSP 3D2 - basic version extended by a double-channel digital stop annunciator

Monitoring units using private radio networks

Another type of vehicle monitoring modules includes units equipped with a modem and a radio station. These units can be embedded in more complex devices and become one of their parts  - e.g. the EPIS 4.0x on-board computers or they can be independent units used for monitoring vehicle positions.

We supply two types of modules for independent vehicle position monitoring using radio networks of transportation companies – the RMU type (radio modem unit):

  • RMU 01     - for vehicle monitoring in the TAIT network – ensures data and voice communication with the dispatching using the TAIT 8255 radio station.
  • RMU 10S    - mainly for transportation company vehicle position monitoring in the FD NET radio network (our product), but it can be SW adapted for other radio networks.