GeolocPVT

GeolocPVT is a standalone navigation app using raw GNSS measurements.

GeolocPVT is a standalone GNSS navigation app (application) that uses information from raw signals transmitted by visible satellites from GPS, Galileo and Beidou constellation systems to compute your position. The app is developed to function without internet connection. The app can be used to record the raw GNSS measurements data for a research or an education application.

Description

It consists of 3 fragments namely monitor, map & options.

Monitor fragment is the default view created when the app is launched. In this fragment you can observe the status of satellites from different constellations, the calculated position in geodetic (Lat, Lon, Alt) and Cartesian (X, Y, Z) coordinates along with date, time in UTC, velocity of the user in m/s. In the map fragment you can visualize your current position and your current path. In the options fragment you can choose which constellation (GPS/Galileo/Beidou or all 3) to use, with or without corrections, single frequency (L1 only)/multi-frequency (L1/L5)/Iono-free solutions, static (Least Squares)/dynamic (TDCP - EKF) scenario and elevation-noise cutoff to remove any measurements below the threshold.

Features

• Can be operated in 2 modes: Static (Lease squares) & Dynamic (TDCP - EKF)

• Can be optimized to deliver single frequency (L1 only), dual frequency (L1/L5) & iono-free solutions

• CN0 (signal quality) based measurement weighting

• Detailed data recording in ASCII text format and also in RINEX v3.01 format (for post processing & research purposes)

• Uses data from raw satellite signals (no internet needed)

Usage recommendation

• The smartphone should be held in hand or attached to a suitable holder

• To get a good first position estimate it is recommended to have the smartphone in obstruction free environments initially

• Smartphone location service should be turned “ON” to get measurements from Android API

• It is necessary to enable “Force Full GNSS Measurements” option from Developer options -> Debugging

• The app background settings should be set to battery saver/no restrictions

• To log data at least one of the 3 options (Pseudorange/position/Ephemeris) should be checked (IMU shall be available in the later versions of the app)

Limitations

• GeolocPVT is a dead reckoning based navigation system resulting in drift in position that persists throughout.

• The app is solely based on the raw measurements coming from the Android location API, so if the measurements are affected it can be clearly seen in the position estimate.

• In deep urban canyon type environments where the measurements are severely affected by the surrounding structures you may experience complete loss of positioning or bad estimates.

• The app works without internet connection but to see the position estimates on a map internet is needed.

• Due to complexity involved in implementing offline maps, this version of the app shall not feature it.

• The app shall refresh ~30 seconds after the first launch because of un-usable measurements coming from the Android API. This is clearly visible to the user. This is a temporary fix but the next version of the app will feature a permanent solution.

How to contribute to the project

• GeolocPVT is an open source application, more information on this project: geoloc.univ-gustave-eiffel.fr/en/hardware/android-application-geolocpvt

• To participate in the code development: Clic here to download the PDF user guide

• Share your comments, queries: [email protected]

Permissions required

• Location: to get access to raw GNSS measurements

• Storage: to log GNSS data for further analysis