Parse NMEA sentences and use the results to show device location on the map.
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
Load an NMEA string and parse the sentences into a series of locations.
Create an NmeaLocationDataSource and initialize it with the mock locations.
Set it to the location display's data source.
Start the location display to begin receiving location and satellite updates.
Relevant API
Location
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.
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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]#ifdef PCH_BUILD#include"pch.hpp"#endif// PCH_BUILD#include"DisplayDeviceLocationWithNmeaDataSources.h"#include"Map.h"#include"MapQuickView.h"#include"NmeaLocationDataSource.h"#include"MapTypes.h"#include"MapViewTypes.h"#include"TaskWatcher.h"#include"LocationDisplay.h"#include"SpatialReference.h"#include"Point.h"#include<QFile>#include<QTimer>usingnamespace Esri::ArcGISRuntime;
DisplayDeviceLocationWithNmeaDataSources::DisplayDeviceLocationWithNmeaDataSources(QObject* parent /* = nullptr */):
QObject(parent),
m_map(newMap(BasemapStyle::ArcGISNavigation, this)),
m_timer(newQTimer(this))
{
}
DisplayDeviceLocationWithNmeaDataSources::~DisplayDeviceLocationWithNmeaDataSources() = default;
voidDisplayDeviceLocationWithNmeaDataSources::init(){
// Register the map view for QML qmlRegisterType<MapQuickView>("Esri.Samples", 1, 0, "MapView");
qmlRegisterType<DisplayDeviceLocationWithNmeaDataSources>("Esri.Samples", 1, 0, "DisplayDeviceLocationWithNmeaDataSourcesSample");
}
MapQuickView* DisplayDeviceLocationWithNmeaDataSources::mapView()const{
return m_mapView;
}
// Set the view (created in QML)voidDisplayDeviceLocationWithNmeaDataSources::setMapView(MapQuickView* mapView){
if (!mapView || mapView == m_mapView)
return;
m_mapView = mapView;
m_mapView->setMap(m_map);
m_mapView->setViewpointCenter(Point(-117.191, 34.0306, SpatialReference::wgs84()), 100'000);
// Create a new NMEA location data source m_nmeaLocationDataSource = newNmeaLocationDataSource(SpatialReference::wgs84(), this);
m_mapView->locationDisplay()->setDataSource(m_nmeaLocationDataSource);
m_mapView->locationDisplay()->setAutoPanMode(LocationDisplayAutoPanMode::Recenter);
emit mapViewChanged();
}
voidDisplayDeviceLocationWithNmeaDataSources::start(){
// Enable receiving NMEA location data from external device m_nmeaLocationDataSource->start();
// Display the user's location m_mapView->locationDisplay()->start();
// Load simulated NMEA sentences for sampleif (m_mockNmeaSentences.isEmpty())
{
const QString filePath = ":/Samples/Maps/DisplayDeviceLocationWithNmeaDataSources/redlands.nmea";
if(!loadMockDataFile(filePath))
{
qDebug() << "Unable to load file at path:" << filePath;
m_nmeaSimulationActive = false;
emit nmeaSimulationActiveChanged();
return;
}
}
// Simulate pushing data to the NMEA location data sourceconnect(m_timer, &QTimer::timeout, this, [this]()
{
const QByteArray line = m_mockNmeaSentences.at(m_mockDataIterator);
// 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 m_nmeaLocationDataSource->pushData(line);
++m_mockDataIterator;
if (m_mockDataIterator >= m_mockNmeaSentences.size())
m_mockDataIterator = 0;
});
m_mockDataIterator = 0;
m_timer->start(1000);
}
voidDisplayDeviceLocationWithNmeaDataSources::reset(){
// Disable simulated data m_timer->stop();
disconnect(m_timer, &QTimer::timeout, nullptr, nullptr);
// Stop displaying user's location m_mapView->locationDisplay()->stop();
// Stop receiving location data m_nmeaLocationDataSource->stop();
}
boolDisplayDeviceLocationWithNmeaDataSources::loadMockDataFile(const QString& filePath){
// Load simulated NMEA sentences to display for sampleQFile mockDataFile(filePath);
if(!mockDataFile.exists())
returnfalse;
mockDataFile.open(QIODevice::ReadOnly);
while (!mockDataFile.atEnd()) {
QByteArray line = mockDataFile.readLine();
// In this simulated data stream, blocks of NMEA sentences start with $GPGGA (which provides the device's position)if (line.startsWith("$GPGGA"))
m_mockNmeaSentences.append(line);
// Additional sentences that provide information such as direction and velocity follow and are separated by line breakselse m_mockNmeaSentences.last() += line;
}
mockDataFile.close();
returntrue;
}