SIM808 – Using GNSS for location tracking

SIM808 is a new Quad band GSM modem with GPRS, GPS and Bluetooth functionality. This small module is a great platform to develop location-based tracking device.



SIM808 has GNSS receivers with the following features

  • 22 tracking /66 acquisition channels
  • GPS L1 C/A code
  • Sensitivity
  • Tracking: -165 dBm
  • Cold starts : -147 dBm
  • Time-To-First-Fix
  • Cold starts: 30s (typ.)
  • Hot starts: 1s (typ.)
  • Warm starts: 28s (typ.)
  • Accuracy: approx 2.5 meters

It has got great sensitivity and resolution and is perfect for developing location-based services.

Connection details

  • Power supply: 5-12V supply can be connected to the module shown in the figure.
  • GPS antenna should be connected to the respective port.
  • The module can be interfaced with PC through RS232 or USB port onboard.
  • It can also be connected to Microcontrollers through Onboard TTL pins.

Note: Appropriate jumper settings are to be used for swapping between RS232 and USB communication

The AT commands are different for the GNSS system, compared with SIM908 GPS commands. GNSS commands can be taken from the SIMCOM GNSS Application Note document to make the internal GPS work. This link can be used to download the required document.

Important commands are listed below.

GNSS command set
Command Description
AT+CGNSPWR GNSS power control
AT+CGNSSEQ GNSS navigation information parsed from NMEA sentences
AT+CGNSINF Serial Clock
AT+CGNSURC GNSS navigation, GEO-fences and speed alarm URC report
AT+CGNSCMD Send command to GNSS
AT+CGNSTST Send data received from GNSS to AT UART

Example command flow

AT+CGNSPWR=1    // Turn on GNSS power

AT+CGNSSEQ=”RMC”  // Define the last NMEA sentence that parsed

AT+CGNSINF   // Read GNSS navigation information


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