GPS Jamming and Interference Detection
Table of Contents
|Dart3-2G and Dart3-4G||All Versions|
|G120-2G and G120-4G||All Versions|
|G70-2G and G70-4G||All Versions|
Our wired devices support GPS Jamming and GPS interference detection. The available parameters are split into 2 tabs in OEM.
For 4G Devices, the GPS Jamming (Adv) tab sets what constitutes 'jamming' or 'interference'
1 = Interference Parameters
2 = Jamming Parameters
For 2G Devices, GPS Jamming (Adv) tab does not let you configure the thresholds but rather uses it's own GPS Jamming parameter set.
GPS 'interference' is represented with a Digital Input. Defaults should generally work well, and are best left untouched unless you know what you are doing.
GPS signals are broadcast at specific frequencies, and GPS receivers (i.e. the device) are tuned to pick these up. Generally, they won't be very strong (they are coming from satellites orbiting about 20 000km away!). So if the module detects signals in this frequency range that are much stronger, or that make up a large proportion of the total signal, it can consider this interference and report it.
When a wired device is in trip, it will leave its GPS on, getting regular fixes and calculating heading, speed, odometer etc. with this data. So if GPS signal is lost for a long time, there is likely a problem, so we flag jamming.
This is set by the Warning Timeout parameter.
GPS Jamming IOs - these parameters determine what action to take should jamming or interference be detected. By default, devices will flag interference, and record a log.
With these parameters we can set which digital inputs the Interference and Jamming flags are mapped to.
|Device||GPS Interference||GPS Jamming|
|Bolt2, Dart3, G70||Digital Input 5||Digital Input 6|
|G120||Digital Input 7||Digital Input 8|
By default, as soon as jamming/interference is detected, a log is created - this will appear as a Digital Input Changed log.
We can set the device to immediately upload if this is detected - however when in trip, the device will be connected to the network anyway - so even with this not set, if detected in trip this will be uploaded immediately.
Jamming/Interference In OEM Server
If JAMW log reason is seen in the device logs, then GPS Jamming/Interference was detected.
Jamming/Interference In Telematics Guru
Alerting on GPS Jamming
Hard-wired devices are already configured to report jamming/interference by default. So we can just set up an alert on TG if we wish to be notified. Simply create an alert and select the input from the list.
Note, these inputs may become active a bit more often than you think. Other electrical signals may cause interference. So it might not be malicious operators with jammers each time you get an alert.
Display on the Live View
We can edit the I/O mappings to display if interference or jamming is detected on the live view
Check for evidence of jamming in the Telemetry
Maybe we have some mysterious events where trips weren't recorded. We can check if the IOs are active in the telemetry.
In telemetry, there are 32 total bits. However in binary, we start counting from 0, right to left, meaning we have bits 0-31. So working right to left 0, 1, 2, 3, 4, we can see bits 5 and 6 highlighted below.