US: Google has publicly released GNSS Analysis app v188.8.131.52 with advanced processing and analysis tools for raw GNSS measurements retrieved from Android devices. The primary intent of these tools is to enable device manufacturers to see in detail how well the GNSS receivers are working in each particular device design, and thus improve the design and GNSS performance in their devices. However, with the tools publicly available, there is also significant value to the research and app developer community.
The v2.5 release builds further on capabilities first announced and made available in 2016 in Android Nougat, when the application programming interfaces (APIs) were introduced, and then updated in May 2017. The latest iteration, announced December 1, now includes the following updates:
- Smoothed pseudoranges.
- Plots of positions from raw andsmoothed pseudorange.
- Plots of measurement errors for raw andsmoothed pseudorange.
- Saves raw and smoothed pseudoranges to derived data file.
- Calculates and saves intersystem time biases to derived data file.
Full details, download links, user manual, and more are available at a Google developers’ blog post: GNSS Analysis Tools. The article also lists Android devices that support raw GNSS measurements. Android powers more than 2 billion devices, and Android phones are made by many different manufacturers.
In its basic and original form, the GNSS Analysis Tool is a desktop application that takes in raw the GNSS Measurements logged from the user’s Android device as input. The desktop application provides interactive plots, organized into three columns showing the behavior of the RF, clock, and measurements.
The user can see the behavior of the GNSS receiver in great detail, including receiver clock offset and drift to the order of 1 nanosecond and 1 ppb and measurement errors on a satellite-by-satellite basis. This enables sophisticated analysis at a level that was previously almost inaccessible to anyone but the chip manufacturers themselves.
The tools support multi-constellation (GPS, GLONASS, Galileo, BeiDou and QZSS) and multi-frequency. The image below shows the satellite locations for L1, L5, E1 and E5 signals tracked by a dual-frequency chip.