Display device location with NMEA data sources

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This sample demonstrates how to parse NMEA sentences and use the results to show device location on the map.

Image of display device location with nmea data sources

Use case

NMEA sentences can be retrieved from GPS receivers and parsed into a series of coordinates with additional information. Devices without a built-in GPS receiver can retrieve NMEA sentences by using a separate GPS dongle, commonly connected via bluetooth or through a serial port.

The NMEA location data source allows for detailed interrogation of the information coming from the GPS receiver. For example, allowing you to report the number of satellites in view.

How to use the sample

Click floating button "Play" to parse the provided NMEA sentences into a location data source, and display the location position and related satellite information. Click "Stop" to stop displaying the location information. The sample will automatically re-center the location data source as it moves across the map.

How it works

  1. Load NMEA sentences from a local file.
  2. Parse the NMEA sentence strings, and push data into NmeaLocationDataSource.
  3. Set the NmeaLocationDataSource to the LocationDisplay's data source.
  4. Start the location display to begin receiving location and satellite updates.

About the data

This sample reads lines from a local file to simulate the feed of data into the NmeaLocationDataSource. This simulated data source provides NMEA data periodically, and allows the sample to be used on devices without a GPS dongle that produces NMEA data.

The route taken in this sample features a one minute driving trip around Redlands, CA.

Relevant API

  • LocationDisplay
  • NmeaLocationDataSource
  • NmeaSatelliteInfo

Offline data

  1. Download the data from ArcGIS Online.
  2. Open your command prompt and navigate to the folder where you extracted the contents of the data from step 1.
  3. Execute the following command:

adb push Redlands.nmea /sdcard/Android/data/com.esri.arcgisruntime.sample.displaydevicelocationwithnmeadatasources/files/Redlands.nmea

Link Local Location
Redlands NMEA <sdcard>/Android/data/com.esri.arcgisruntime.sample.displaydevicelocationwithnmeadatasources/files/Redlands.nmea

Tags

GPS, history, navigation, NMEA, real-time, trace

Sample Code

MainActivity.kt
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/* Copyright 2021 Esri
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

package com.esri.arcgisruntime.sample.displaydevicelocationwithnmeadatasources

import android.os.Bundle
import android.util.Log
import android.widget.TextView
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import androidx.appcompat.content.res.AppCompatResources
import com.esri.arcgisruntime.ArcGISRuntimeEnvironment
import com.esri.arcgisruntime.geometry.Point
import com.esri.arcgisruntime.geometry.SpatialReferences
import com.esri.arcgisruntime.location.LocationDataSource
import com.esri.arcgisruntime.location.NmeaLocationDataSource
import com.esri.arcgisruntime.location.NmeaSatelliteInfo
import com.esri.arcgisruntime.mapping.ArcGISMap
import com.esri.arcgisruntime.mapping.BasemapStyle
import com.esri.arcgisruntime.mapping.Viewpoint
import com.esri.arcgisruntime.mapping.view.LocationDisplay
import com.esri.arcgisruntime.mapping.view.MapView
import com.esri.arcgisruntime.sample.displaydevicelocationwithnmeadatasources.databinding.ActivityMainBinding
import com.google.android.material.floatingactionbutton.FloatingActionButton
import java.io.BufferedReader
import java.io.File
import java.io.FileReader
import java.nio.charset.StandardCharsets
import java.util.*
import kotlin.collections.ArrayList
import kotlin.concurrent.timerTask

class MainActivity : AppCompatActivity() {

    private val TAG = MainActivity::class.java.simpleName

    // Create a new NMEA location data source
    private val nmeaLocationDataSource: NmeaLocationDataSource =
        NmeaLocationDataSource(SpatialReferences.getWgs84())

    // Location datasource listener
    private var locationDataSourceListener: LocationDataSource.StatusChangedListener? = null

    // Create a timer to simulate a stream of NMEA data
    private var timer = Timer()

    // Keeps track of the timer during play/pause
    private var count = 0

    private val activityMainBinding by lazy {
        ActivityMainBinding.inflate(layoutInflater)
    }

    private val mapView: MapView by lazy {
        activityMainBinding.mapView
    }

    private val accuracyTV: TextView by lazy {
        activityMainBinding.accuracyTV
    }

    private val satelliteCountTV: TextView by lazy {
        activityMainBinding.satelliteCountTV
    }

    private val satelliteIDsTV: TextView by lazy {
        activityMainBinding.satelliteIDsTV
    }

    private val systemTypeTV: TextView by lazy {
        activityMainBinding.systemTypeTV
    }

    private val playPauseFAB: FloatingActionButton by lazy {
        activityMainBinding.playPauseFAB
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(activityMainBinding.root)

        // Authentication with an API key or named user is required
        // to access basemaps and other location services
        ArcGISRuntimeEnvironment.setApiKey(BuildConfig.API_KEY)

        // Create a map with the Basemap style and set it to the MapView
        val map = ArcGISMap(BasemapStyle.ARCGIS_NAVIGATION)
        mapView.map = map

        // Set a viewpoint on the map view centered on Redlands, California
        mapView.setViewpoint(
            Viewpoint(
                Point(-117.191, 34.0306, SpatialReferences.getWgs84()),
                100000.0
            )
        )

        // Set the NMEA location data source onto the map view's location display
        val locationDisplay = mapView.locationDisplay
        locationDisplay.locationDataSource = nmeaLocationDataSource
        locationDisplay.autoPanMode = LocationDisplay.AutoPanMode.RECENTER

        // Disable map view interaction, the location display will automatically center on the mock device location
        mapView.interactionOptions.isPanEnabled = false
        mapView.interactionOptions.isZoomEnabled = false

        playPauseFAB.setOnClickListener {
            if (!nmeaLocationDataSource.isStarted) {
                // Start location data source
                displayDeviceLocation()
                setLocationStatus(true)
            } else {
                // Stop receiving and displaying location data
                nmeaLocationDataSource.stop()
                setLocationStatus(false)
            }
        }
    }

    /**
     * Sets the FAB button to "Start"/"Stop" based on the argument [isShowingLocation]
     */
    private fun setLocationStatus(isShowingLocation: Boolean) = if (isShowingLocation) {
        playPauseFAB.setImageDrawable(
            AppCompatResources.getDrawable(
                this,
                R.drawable.ic_round_pause_24
            )
        )
    } else {
        playPauseFAB.setImageDrawable(
            AppCompatResources.getDrawable(
                this,
                R.drawable.ic_round_play_arrow_24
            )
        )
    }

    /**
     * Initializes the location data source, reads the mock data NMEA sentences, and displays location updates from that file
     * on the location display. Data is pushed to the data source using a timeline to simulate live updates, as they would
     * appear if using real-time data from a GPS dongle
     */
    private fun displayDeviceLocation() {
        val simulatedNmeaDataFile = File(getExternalFilesDir(null)?.path + "/Redlands.nmea")
        if (simulatedNmeaDataFile.exists()) {
            try {
                // Read the nmea file contents using a buffered reader and store the mock data sentences in a list
                val bufferedReader = BufferedReader(FileReader(simulatedNmeaDataFile.path))
                // Add carriage return for NMEA location data source parser
                val nmeaSentences: MutableList<String> = mutableListOf()
                var line = bufferedReader.readLine()
                while (line != null) {
                    nmeaSentences.add(line + "\n")
                    line = bufferedReader.readLine()
                }
                bufferedReader.close()

                // Set up the accuracy for each location change
                nmeaLocationDataSource.addLocationChangedListener {
                    //Convert from Meters to Foot
                    val horizontalAccuracy = it.location.horizontalAccuracy * 3.28084
                    val verticalAccuracy = it.location.verticalAccuracy * 3.28084
                    accuracyTV.text = "Accuracy- Horizontal: %.1fft, Vertical: %.1fft".format(
                        horizontalAccuracy,
                        verticalAccuracy
                    )
                }

                // Handle when LocationDataSource status is changed
                locationDataSourceListener = LocationDataSource.StatusChangedListener {
                    if (it.status == LocationDataSource.Status.STARTED) {
                        // Add a satellite changed listener to the NMEA location data source and display satellite information
                        setupSatelliteChangedListener()

                        timer = Timer()
                        // Push the mock data NMEA sentences into the data source every 250 ms
                        timer.schedule(timerTask {
                            // Only push data when started
                            if (it.status == LocationDataSource.Status.STARTED)
                                nmeaLocationDataSource.pushData(
                                    nmeaSentences[count++].toByteArray(
                                        StandardCharsets.UTF_8
                                    )
                                )
                            // Reset the count after the last data point is reached
                            if (count == nmeaSentences.size)
                                count = 0
                        }, 250, 250)

                        setLocationStatus(true)
                    }
                    if (it.status == LocationDataSource.Status.STOPPED) {
                        timer.cancel()
                        nmeaLocationDataSource.removeStatusChangedListener(
                            locationDataSourceListener
                        )
                        setLocationStatus(false)
                    }
                }

                // Initialize the location data source and prepare to begin receiving location updates when data is pushed
                // As updates are received, they will be displayed on the map
                nmeaLocationDataSource.addStatusChangedListener(locationDataSourceListener)
                nmeaLocationDataSource.startAsync()


            } catch (e: Exception) {
                Toast.makeText(
                    this,
                    "Error while setting up NmeaLocationDataSource: " + e.message,
                    Toast.LENGTH_SHORT
                ).show()
                Log.e(TAG, "Error while setting up NmeaLocationDataSource: " + e.message.toString())
            }
        } else {
            Toast.makeText(this, "NMEA File not found", Toast.LENGTH_SHORT).show()
        }
    }

    /**
     * Obtains NMEA satellite information from the NMEA location data source, and displays satellite information on the app
     */
    private fun setupSatelliteChangedListener() {
        nmeaLocationDataSource.addSatellitesChangedListener {
            val uniqueSatelliteIDs: HashSet<Int> = hashSetOf()
            // Get satellite information from the NMEA location data source every time the satellites change
            val nmeaSatelliteInfoList: List<NmeaSatelliteInfo> = it.satelliteInfos
            // Set the text of the satellite count label
            satelliteCountTV.text = "Satellite count- " + nmeaSatelliteInfoList.size

            for (satInfo in nmeaSatelliteInfoList) {
                // Collect unique satellite ids
                uniqueSatelliteIDs.add(satInfo.id)
                // Sort the ids numerically
                val sortedIds: MutableList<Int> = ArrayList(uniqueSatelliteIDs)
                sortedIds.sort()
                // Display the satellite system and id information
                systemTypeTV.text = "System- " + satInfo.system
                satelliteIDsTV.text = "Satellite IDs- $sortedIds"
            }
        }
    }

    override fun onPause() {
        mapView.pause()
        super.onPause()
    }

    override fun onResume() {
        super.onResume()
        mapView.resume()
    }

    override fun onDestroy() {
        nmeaLocationDataSource.stop()
        mapView.dispose()
        super.onDestroy()
    }
}

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