Real-Time GNSS Android App

Overview

The Real-Time GNSS Android App collects GNSS measurements from the device and transmits the data to a specified server for further processing and visualization. It provides real-time GNSS data such as latitude, longitude, altitude, pseudorange rate, CN0, Doppler shift, and computed ECEF (Earth-Centered, Earth-Fixed) coordinates.

Features

• Real-Time GNSS Data Collection: Captures GNSS measurements from the device.
• Data Transmission: Sends collected GNSS data to a specified server.
• Data Display: Displays latitude, longitude, altitude, pseudorange rate, CN0, Doppler shift, and ECEF coordinates on the app UI.
• Socket Communication: Establishes a socket connection to transmit GNSS data to the server.
• Location Updates: Uses Android's LocationManager to receive location updates.

Requirements

• Android device with API level 24 or higher.
• Permissions for accessing fine location (ACCESS_FINE_LOCATION).
• A server to receive and process the GNSS data.

Permissions

Ensure the following permissions are added to your AndroidManifest.xml:

<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.INTERNET" /> 

Dependencies

Add the following dependencies to your build.gradle file:

dependencies {
    implementation 'com.google.code.gson:gson:2.8.8'
    implementation 'androidx.appcompat:appcompat:1.2.0'
}

Usage

1. Configure Server IP and Port: Replace SERVER_IP and SERVER_PORT with the IP address and port number of your server in MainActivity.java:

    private static final String SERVER_IP = "192.168.43.53"; // Replace with your server's IP address
    private static final int SERVER_PORT = 5001; // Replace with your server's port number

2. Start the App: Build and run the app on an Android device.
3. Permissions Request: The app will request permission to access the device's location. Ensure you grant this permission.
4. View Data: The app will display real-time GNSS data on the UI. It will also transmit this data to the specified server.

Code Overview

MainActivity.java

The MainActivity class handles the GNSS data collection, processing, and transmission. It implements the LocationListener interface to receive location updates.

• GNSS Data Collection: Uses LocationManager to request location updates and register GnssMeasurementsCallback to receive GNSS measurements.

• Socket Communication: Establishes a socket connection to the server and sends GNSS data as JSON strings.

• UI Update: Displays the received GNSS data on the app's UI elements.

• Data Processing: Converts latitude, longitude, and altitude to ECEF coordinates.

Example Code Snippets

Registering GNSS Measurements Callback

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
    locationManager.registerGnssMeasurementsCallback(new GnssMeasurementsEvent.Callback() {
        @Override
        public void onGnssMeasurementsReceived(@NonNull GnssMeasurementsEvent event) {
            super.onGnssMeasurementsReceived(event);
            for (GnssMeasurement measurement : event.getMeasurements()) {
                cn0DbHz = measurement.getCn0DbHz();
                pseudorangeRateMetersPerSecond = measurement.getPseudorangeRateMetersPerSecond();
                dopplerShift = pseudorangeRateMetersPerSecond; // Use pseudorange rate as Doppler shift

                // Calculate x, y, z here using your Python logic converted to Java
                calculateSatellitePosition();

                Log.d("MainActivity", "Sending GNSS data");
                sendCombinedData();
            }
        }
    }, null);
}

Sending Data to the Server

private void sendCombinedData() {
    Map<String, Object> combinedData = new HashMap<>();
    combinedData.put("latitude", latitude);
    combinedData.put("longitude", longitude);
    combinedData.put("altitude", altitude);
    combinedData.put("pseudorangeRate", pseudorangeRateMetersPerSecond);
    combinedData.put("cn0", cn0DbHz);
    combinedData.put("doppler", dopplerShift);
    combinedData.put("x", x);
    combinedData.put("y", y);
    combinedData.put("z", z);

    Gson gson = new Gson();
    String json = gson.toJson(combinedData);
    Log.d("MainActivity", "Sending JSON: " + json);

    if (writer != null) {
        new Thread(() -> {
            Log.d("MainActivity", "Sending data to server");
            writer.println(json);
        }).start(); // Ensure this runs in a background thread
    }

    runOnUiThread(() -> {
        pseudorangeText.setText("Pseudo-Range Rate: " + pseudorangeRateMetersPerSecond);
        cn0Text.setText("CN0: " + cn0DbHz);
        dopplerText.setText("Doppler: " + dopplerShift);
        xText.setText("X: " + x);
        yText.setText("Y: " + y);
        zText.setText("Z: " + z);
    });
}