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.

screenshot

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 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

Tap "Start" to parse the NMEA sentences into a simulated location data source, and initiate the location display. Tap "Reset" to reset the location display.

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 location display's data source.
  4. Start the location display to begin receiving location and satellite updates.

Relevant API

  • LocationDisplay
  • NmeaLocationDataSource

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.

Tags

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

Sample Code

DisplayDeviceLocationWithNmeaDataSources.qml
                                                                                                                                              
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// [WriteFile Name=DisplayDeviceLocationWithNmeaDataSources, Category=Maps]
// [Legal]
// 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.
// [Legal]

import QtQuick 2.6
import QtQuick.Controls 2.2
import Esri.ArcGISRuntime 100.12
import Esri.ArcGISExtras 1.1

Rectangle {
    id: rootRectangle
    clip: true
    width: 800
    height: 600

    property bool nmeaSimulationActive: false
    property var mockNmeaData: []

    MapView {
        id: mapView
        anchors.fill: parent

        Map {
            id: map
            Basemap {
                initStyle: Enums.BasemapStyleArcGISNavigation
            }
            ViewpointCenter {
                Point {
                    x: -117.191
                    y: 34.0306
                    spatialReference: SpatialReference { wkid: 4326 }
                }
                targetScale: 100000
            }
        }

        // Create the NemaLocationDataSource to push NMEA sentences to
        locationDisplay.dataSource: NmeaLocationDataSource {
            id: nmeaLocationDataSource
            receiverSpatialReference: SpatialReference { wkid: 4326 }
        }
        locationDisplay.autoPanMode: Enums.LocationDisplayAutoPanModeRecenter
    }

    Button {
        id: button
        anchors {
            horizontalCenter: parent.horizontalCenter
            bottom: parent.bottom
            margins: 25
        }
        width: 200
        text: nmeaSimulationActive ? "RESET" : "START"
        onClicked: {
            nmeaSimulationActive = !nmeaSimulationActive;
            if (nmeaSimulationActive)
                startSimulation();
            else
                endSimulation();
        }
    }

    FileFolder {
        id: mockNmeaDataFile
        path: ":/Samples/Maps/DisplayDeviceLocationWithNmeaDataSources/redlands.nmea"
        Component.onCompleted: {
            // Load simulated NMEA sentences to display for sample
            readFile(path)
            .toString()
            .split("\n")
            .forEach(
                 (line) => {
                     // In this simulated data stream, blocks of NMEA sentences start with $GPGGA (which provides the device's position)
                     if (line.startsWith("$GPGGA"))
                         mockNmeaData.push(line + "\n");

                     // Additional sentences that provide information such as direction and velocity follow and are separated by line breaks
                     else
                         mockNmeaData[mockNmeaData.length-1] += (line + "\n");
                 });
        }
    }

    // This timer is used to simulate NMEA sentences being received at regular intervals
    Timer {
        id: timer
        interval: 1000
        repeat: true
        property var count: 0
        onTriggered: {
            try {
                // In a non-simulated scenario, incoming NMEA sentences from a serial port or bluetooth device would be pushed to the location data source in real time
                // NMEA sentences can be pushed individually or in multiple lines separated by line breaks
                // Sentences pass information such as direction, velocity, and location and are grouped together to provide detailed information about a user's position
                nmeaLocationDataSource.pushData(mockNmeaData[count]);
            } catch(err) {
                console.log("Unable to push: " + mockNmeaData[count]);
                console.log(err);
            }

            count++;
            if (count >= mockNmeaData.length)
                count = 0;
        }
    }

    function startSimulation() {
        // Enable receiving NMEA location data from external device
        nmeaLocationDataSource.start();

        // Display the user's location
        mapView.locationDisplay.start();

        // Begin simulated data stream
        timer.count = 0;
        timer.start();
    }

    function endSimulation() {
        // End simulated data stream
        timer.stop();

        // Stop displaying the user's location
        mapView.locationDisplay.stop();

        // Stop receiving location data
        nmeaLocationDataSource.stop();
    }
}

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