Google launched version 188.8.131.52 of the GnssLogger in the Play Store with several new features.
The Android Framework provides access to raw GNSS measurements on several Android devices.
Original equipment manufacturers (OEMs), developers, and researchers can make use of the tools in this page to test new phone designs, validate functionality, develop new algorithms, evaluate improvements to the GNSS system implementation as well as building value added apps.
SUPL Client Sample Code
Suplclient is sample code that accesses supl.google.com to obtain real time ephemeris. The
SuplTester class provides an example on how to use the SUPL Client Project. The
SuplTester sets up the SUPL TCP connection specifications, then at a given latitude and longitude sends an LPP SUPL request and prints the SUPL server response.
Antenna calibration information
Starting in Android 11 (API level 30), you can use the
GnssAntennaInfo class to access
antenna characteristics, such as: phase center offset (PCO) coordinates, phase
center variation (PCV) corrections, and signal gain corrections. These
corrections can be applied to the raw measurements to improve accuracy.
GnssAntennaInfo, keep the following system behaviors in mind. They
are designed to enhance user privacy.
- The characteristics supplied by this API are only specific to the device model, not an individual device.
- Use of the
GnssAntennaInfoclass requires the
Logging raw measurements
You can use Android Studio to build an app that captures raw GNSS measurements and other location data and logs them to a file. For example source code of such an app, see GPS Measurement Tools.
Google GNSSLogger is a sample app that is developed with this functionality. To get GNSS output with the sample app, your device must support raw GNSS measurements.
Once you have captured the GNSS log using the GNSS Logger, you can copy the log files from the device to your computer for further analysis. From within the GNSS Logger you can send the files to yourself via email or save them to Google Drive. Alternatively, you can save the files using the file management app on the device, or you can use the Android Debug Bridge (ADB) as explained in Copy files to/from a device.
Analyzing raw measurements
The GNSS Analysis app reads the GPS/GNSS raw measurements collected by the GNSS Logger and uses them to analyze the GNSS receiver behavior, as shown in figure 1.
The GNSS Analysis app is built on MATLAB, but you don't need to have MATLAB to run it. The app is compiled into an executable that installs a copy of the MATLAB Runtime.
GNSS Analysis Control Panel
The GNSS Analysis control panel, shown in figure 2, lets you manage app features, such as:
- Select which satellites are displayed.
- Control the reference position, velocity, and time (PVT) used for calculating measurement errors.
- Generate analysis reports.
- Define a window in the data between start and end times.
GNSS Analysis interactive plots
The GNSS Analysis app provides interactive plots organized in radio frequency (RF), clocks, and measurements columns, as shown in figure 3.
The RF column shows the following data:
- For each constellation, the four satellites with the strongest signals.
- For each satellite, the time plot of carrier to noise density (C/No).
- The skyplot of satellite positions.
The clock column shows the following data:
- The pseudoranges.
The offset frequency of the receiver clock, which is computed using one of the following reference positions:
- Automatically computed mean position.
- Latitude, longitude, and altitude entered by the user.
- National Marine Electronics Association (NMEA) file with truth reference PVT.
The offset of the standby clock that keeps time when the receiver resets the duty cycle of the primary oscillator.
The measurements column shows the following data:
- The weighted least squares position results obtained from the raw pseudoranges. The weighting is done using the reported uncertainty of each measurement, which is part of the raw measurement API spec.
- The errors of each pseudorange for each measurement.
The errors of each pseudorange rate for each measurement.
GNSS Analysis test report
GNSS Analysis can generate a test report, as shown in figure 4, that evaluates the API implementation, received signal, clock behavior, and measurement accuracy. For each case, the app reports whether the receiver passed or failed the test based on the performance measured against known benchmarks. The test report is useful for device manufacturers, who can use it as they iterate through the design and implementation of new devices. To generate the test report, click Make Report.
The Compare tab provides a side-by-side comparison, shown in figure 5, of C/No from several GNSS log files, which is useful when comparing the RF performance of several devices.
- Read data captured with the GNSS Logger sample app.
- Compute and visualize pseudoranges.
- Compute weighted least squares position and velocity.
- View and analyze carrier phase.
GNSS Analysis app v184.108.40.206 release notes
GNSS Analysis app version 220.127.116.11 includes the following updates:
- Supports GnssLogger files and RINEX v3 observation files collected from GnssLogger v18.104.22.168
- Supports more signals like BDS B2, GAL E5 in position computations
- Adapts to the connection change to NASA CDDIS site (now uses HTTPS instead of FTP)
- Fixes some known bugs
We want to improve the support for GNSS on Android. Let us know about any issues with GNSS support on Android by using the GNSS issue tracker. Please check if your issue has already been addressed in the FAQ before posting it.
You can find answers to frequently asked questions in the GNSS Analysis Tools FAQs.