GPS monitoring of police vehicles

The FMC650 works on a 4G LTE Cat 1 network and falls back to 2G by itself if LTE disappears. It is a tracker from the PROFESSIONAL range: it has plenty of inputs and outputs, CAN support and the ability to connect external sensors and readers. The data goes not into a public cloud but over a VPN to the police server and database.

Crew status is transmitted in a simple and reliable way. A small keypad or external device is wired to the tracker's analogue input, producing a different voltage for each button. For instance 5 V means "Ready", other values mean "Busy", "Meal break" or "En route to call". The tracker distinguishes the voltage levels and sends the status along with the coordinates. The operator sees on the map not just dots but vehicles with a clear label showing who can be dispatched right now.

A digital input records when the siren and the beacons are switched on. From that data it is straightforward to reconstruct later when a crew was travelling to a call under priority and when it was simply moving around the district.

An LV-CAN200 adapter takes data off the vehicle's CAN bus without cutting into the wiring: door status, mileage, fuel consumption and fuel level, engine revolutions, temperature, accelerator pedal position. For the police the rear door matters most of all: if it opens while a detainee is in the vehicle, the system can raise an alert immediately.

Access to the vehicle is restricted through driver identification. The officer presents an RFID card or an iButton key, and the tracker records who took the car. It can be set up so that without authorisation the system raises an alert or blocks starting through a relay.

Service reminders are built on mileage or engine hours. When a car approaches its oil or brake pad change interval, the person responsible receives a notification in advance instead of hearing about the problem from a crew stranded on the hard shoulder.

The dispatcher ends up working with a single map: where the cars are, what status each has, who is driving, whether the siren is on, whether everything is in order mechanically. When a call comes in, the nearest free crew is chosen in seconds.

Imagine an ordinary night. A call comes in about a break-in at a shop. There are three cars nearby on the map: one with the status "Busy", a second on a meal break two kilometres away, a third free but further off. The operator sees this at once and decides for himself whom to pull off the break, instead of calling each of them in turn on the radio and waiting for an answer. In the morning the shift supervisor opens a report and sees how many minutes the crew took to reach the address and whether the siren was used.

What counts as a call attended. A car driving past an address does not yet mean the crew dealt with the call. In a report for management it is therefore better to separate three marks: the time the crew pressed "En route to call", the time of entry into the geofence around the address, and the time the status changed back to "Ready". The first and third marks are crew actions on the keypad, the second is a GPS measurement. Discrepancies between them show where statuses are being forgotten.

It is worth stating the source of each figure in the report itself: coordinates and speed come from the tracker's GNSS, mileage and doors from the CAN bus, the driver from RFID or iButton, the siren from a digital input. Then, when a complaint is investigated, it is clear which figure was measured by an instrument and which was entered by a person.

Limitations. The response time measured by GPS depends on the logging interval and on signal quality among dense buildings. If timing accurate to the second is needed, the reporting interval while the status is "En route to call" is set more frequent than during ordinary patrolling.