Decoding GNSS navigation messages on Android

Looking at the Android documentation

Gets the type of the navigation message contained in the object.

Looking at the raw data

Decoding the data

For GPS L1 C/A, IRNSS L5 C/A, Beidou D1 & Beidou D2, each subframe contains 10 30-bit words. Each word (30 bits) should be fit into the last 30 bits in a 4-byte word (skip B31 and B32), with MSB first, for a total of 40 bytes, covering a time period of 6, 6, and 0.6 seconds, respectively.

For Glonass L1 C/A, each string contains 85 data bits, including the checksum. These bits should be fit into 11 bytes, with MSB first (skip B86-B88), covering a time period of 2 seconds.…

For Galileo I/NAV, each page contains 2 page parts, even and odd, with a total of 2x114 = 228 bits, (sync & tail excluded) that should be fit into 29 bytes, with MSB first (skip B229-B232).

The structure of the GPS L1 C/A navigation message (Source: Navipedia)

Wait…do we even need navigation messages from the Android API?

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.

Closing thoughts

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