Vehicle Telematics in Mobile IoT App

Implementing Vehicle Telematics in Mobile IoT Applications

Vehicle telematics collects data from moving objects: GPS coordinates, speed, mileage, driver behavior (hard acceleration, braking), fuel consumption, refrigerated body temperature. Data flows from onboard tracker via GPRS/LTE to server; mobile app is a dispatcher or fleet manager tool. Development breaks into three layers: tracker protocol, server platform, mobile client.

GPS Tracker Protocols

Trackers communicate via several common protocols:

For parsing tracker protocols, use Traccar — open-source server platform supporting 200+ protocols. Traccar runs on your server, accepts tracker data and provides REST API + WebSocket for mobile clients. This is the most sensible starting path.

Traccar API: Android Integration

// Retrofit interface to Traccar API
interface TraccarApi {
    @GET("devices")
    suspend fun getDevices(
        @Query("all") all: Boolean = false,
        @Query("groupId") groupId: Long? = null,
    ): List<Device>

    @GET("positions")
    suspend fun getLatestPositions(
        @Query("deviceId") deviceId: Long? = null,
    ): List<Position>

    @GET("reports/trips")
    suspend fun getTrips(
        @Query("deviceId") deviceId: Long,
        @Query("from") from: String,  // ISO 8601
        @Query("to") to: String,
    ): List<Trip>
}

data class Position(
    val id: Long,
    val deviceId: Long,
    val latitude: Double,
    val longitude: Double,
    val speed: Double,     // knots, convert to km/h * 1.852
    val course: Double,
    val altitude: Double,
    val accuracy: Double,
    val fixTime: String,
    val valid: Boolean,
    val attributes: Map<String, Any>,  // battery, ignition, mileage, etc.
)

Real-time updates via Traccar WebSocket:

class TraccarWebSocketClient(private val baseUrl: String, private val token: String) {
    private val okHttpClient = OkHttpClient.Builder()
        .readTimeout(0, TimeUnit.MILLISECONDS)  // infinite timeout for WS
        .build()

    fun connect(): Flow<TraccarEvent> = callbackFlow {
        val request = Request.Builder()
            .url("wss://${baseUrl}/api/socket")
            .header("Cookie", "JSESSIONID=$token")
            .build()

        val ws = okHttpClient.newWebSocket(request, object : WebSocketListener() {
            override fun onMessage(webSocket: WebSocket, text: String) {
                val event = json.decodeFromString<TraccarSocketMessage>(text)
                event.positions?.forEach { trySend(TraccarEvent.Position(it)) }
                event.devices?.forEach { trySend(TraccarEvent.DeviceUpdate(it)) }
                event.events?.forEach { trySend(TraccarEvent.Alert(it)) }
            }

            override fun onFailure(webSocket: WebSocket, t: Throwable, response: Response?) {
                close(t)
            }
        })
        awaitClose { ws.close(1000, "Closed") }
    }
}

Map with Live Markers

Google Maps SDK on Android with custom vehicle markers:

class FleetMapFragment : Fragment() {
    private lateinit var map: GoogleMap
    private val vehicleMarkers = HashMap<Long, Marker>()

    private fun updateVehiclePosition(position: Position) {
        val latLng = LatLng(position.latitude, position.longitude)
        val marker = vehicleMarkers[position.deviceId]

        if (marker == null) {
            val newMarker = map.addMarker(
                MarkerOptions()
                    .position(latLng)
                    .icon(getBitmapDescriptor(R.drawable.ic_truck, position.course))
                    .title(getVehicleName(position.deviceId))
            )
            vehicleMarkers[position.deviceId] = newMarker!!
        } else {
            // Animate marker movement
            animateMarker(marker, latLng, position.course)
        }
    }

    private fun animateMarker(marker: Marker, to: LatLng, bearing: Float) {
        val animator = ValueAnimator.ofFloat(0f, 1f).apply {
            duration = 1000
            interpolator = LinearInterpolator()
        }
        val from = marker.position
        animator.addUpdateListener { anim ->
            val fraction = anim.animatedValue as Float
            marker.position = LatLng(
                from.latitude + (to.latitude - from.latitude) * fraction,
                from.longitude + (to.longitude - from.longitude) * fraction,
            )
            marker.rotation = bearing
        }
        animator.start()
    }
}

Marker animation between positions is a detail often missed. Without it, the icon jumps across the map.

Driver Behavior Analytics

Hard acceleration (> 0.3g), braking (> 0.4g), sharp turns — events from tracker accelerometer, arrive in position attributes. Driver scoring calculated on backend, sent to app as daily/weekly aggregate: percentage of time with speeding, count of harsh events, rating 0-100.

Geofences — zones on map; entry/exit generates event. Add geofence from mobile app: draw polygon on map, send coordinates to Traccar Geofences API.

Offline and Cache

Dispatcher watches the app constantly; if server is down 5 minutes, can't show empty map. Cache latest positions of all vehicles in Room. On startup show cache, update via WebSocket. Last update timestamp visible in header.

Developing dispatcher app with map, real-time positions via Traccar and trip reports: 5-8 weeks. Full telematics platform with driver analytics, geofences and CAN data integration: 3-4 months. Cost calculated individually after analyzing fleet size and platform requirements.