Environmental Context Indicator for Evaluating Quality of GNSS Observation Environment Using Android Smartphone

Area of Science:

• Geomatics Engineering
• Mobile Computing
• Signal Processing

Background:

• Location-based services are increasingly integrated into daily life via smartphones.
• Reliable localization from smartphone Global Navigation Satellite Systems (GNSS) is crucial but challenged by environmental variability.
• Localization uncertainty necessitates methods to assess GNSS observation quality.

Purpose of the Study:

• To develop an Environmental Context Indicator (ECI) for continuous and interpretable GNSS observation quality assessment.
• To quantify the impact of environmental factors on GNSS signal reception and accuracy.
• To provide a metric reflecting real-world GNSS performance on smartphones.

Main Methods:

• Developed an ECI using carrier-to-noise density ratio (C/N0), visible satellite count, and positional dilution of precision (PDOP).
• Utilized a Samsung Galaxy S21+ to collect data from GPS (L1/L5), Galileo (E1/E5), and BeiDou (B1) satellite signals.
• Constructed the ECI with real-valued (0-6), integer-valued (1-5), and reliability ratio components.

Main Results:

• The ECI successfully reflected environmental variations and corresponding GNSS quality changes.
• ECI values were lowest in open areas and increased towards urban and indoor environments.
• ECI demonstrated sensitivity to building density, showing significant fluctuations in urban areas.

Conclusions:

• The developed ECI provides a valuable tool for understanding and communicating GNSS observation quality in diverse environments.
• ECI's performance indicates its potential for improving the reliability of location-based services.
• Environmental context significantly influences smartphone GNSS performance, necessitating context-aware localization strategies.