Measuring instruments and equipment: Swiss Quality

Inertial Navigation System


Compact GNSS-aided inertial navigation system Nav-2M is based on compact MEMS inertial sensors and as a source of reference navigation data it utilizes built in GPS/GLONASS receiver. System can be installed on any type of railway vehicle. The system determines position coordinates (latitude, longitude and height) and attitude angles (pitch, roll and heading) along with accelerations and angular rates of the vehicle body motion with respect to the local-level frame. The MEMS sensors are 3 accelerometers and 3 angular rate sensors, magnetometer and a barometric altimeter. The magnetometer is used only for internal reference purposes and can not be used as a reference source of magnetic heading data.

The Nav-2M system can function as a primary or supporting source of navigation and attitude data. The data is output via standard serial interface RS 232 or optionally via RS422 interface.

Although the system incorporates built in GPS/GLONASS receiver, the unit can be connected to external GNSS receiver per customer request. The external receiver must be capable of NMEA 0183 data output.

System configuration

Nav-2M consists of:
  • MEMS Sensor and Digital Processing Unit (SDSPU) with built in GNSS receiver. The sensors located inside the unit provide acceleration and angular rate measurements with respect to body frame, as well as barometric height and satellite navigation system data. The built-in digital processor performs real-time data processing, runs navigation algorithm and calculates the output data.
  • GNSS Antenna
  • Commutation cables
GNSS  Antenna. Model 2J433
GNSS Antenna
Model 2J433

SDPSU housing has two LED indicators, barometric sensor input tube, data/power connector and GNSS antenna connector.

The Nav-2M standard configuration includes Navis NV08С-SCN GPS/GLONASS receiver and 3V active micropatch antenna with magnetic mount.


Dynamic Ranges
Roll deg ±180
Pitch deg ±90
Accelerations g ±6
Heading deg 0..360
Angular rate deg/sec ±250
Max. calibrated altitude
(for barometric altimeter)
Accuracy   GNSS On GNSS off INS+ADS
Position m RMS 5 (*) 500 (**) 50 (**)
X,Y Velocity m/s RMS 0.2 5 (**) 1
Z Velocity m/s RMS 0.28 0.5 0.5
Pitch and Roll
Straight motion deg RMS 0.2÷0.3 0.3÷0.5 0.3÷0.5
Maneuver deg RMS 0.4÷0.6 0.7÷1 0.6÷0.7
Heading (tracking angle) deg RMS 0.5 3 (**) 3 (**)
Altitude m 2..4 6 6
Update rate Hz 50 (optionally 10)
Fully stabilized data sec 30
Output signal type RS232, RS422 (option)
Data format proprietary binary
Input voltage VDC 10-30
Input current (at 12 VDC) A 0.17
Power consumption
(including GNSS receiver)
W 3 (max)
Operating temperature deg C -20 to +40
Non-operating temperature deg C -40 to +75
Humidity % <98
Atmospheric pressure kPa 20-113
Operating vibration (sine) g RMS ±2
Shock (5 ms) g 20
Size in
4.9 x 3.1 x 2.2
12.5 x 8.0 x 5.7
Weight lbs

(*) Depends on GNSS receiver accuracy

(**) 5 min GNSS gap

Fin-de-Praz 24, CH-2024 St-Aubin-Sauges, Switzerland      phone +41 (0)32 835 35 15