GNSSResearch » History » Version 3
dl lud, 06/24/2024 10:07 PM
add details to PSDS
| 1 | 1 | dl lud | h1. GNSS Research |
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| 3 | 2 | dl lud | Research into satellite navigation, aka SatNav or Global Navigation Satellite Systems (GNSS) and related technologies. |
| 4 | Example systems: GPS, GLONASS, Galileo, BeiDou. |
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| 6 | h2. Assisted GNSS (A-GNSS) |
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| 8 | Also known as Assisted GPS (A-GPS). Greatly improves the Time To First Fix (TTFF) by downloading almanac and ephemeris data via mobile broadband or WiFi, instead of waiting for the slow download via the GNSS signal. |
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| 10 | h3. SUPL |
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| 12 | 2 | dl lud | SUPL (Secure User Plane Location) is the most common protocol used to retrieve the current almanac and ephemeris data. |
| 13 | 1 | dl lud | There are no free software SUPL servers that we know off. Android uses Google's servers (@supl.google.com@) by default. Most carriers also default to @supl.google.com@ on their APN. GrapheneOS runs a proxy at @supl.grapheneos.org@. |
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| 15 | h3. PSDS |
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| 17 | 3 | dl lud | PSDS (Predicted Satellite Data Service) is the generic name for a server that provides long-term (usually weekly) forecasts of satellite positions. It allows fast TTFF for several days even without an internet connection. |
| 18 | The data format is vendor specific. There is an implementation from Qualcomm (known as gpsOneXTRA or just XTRA) and another by Broadcom ("which downloads 3 files":https://discuss.grapheneos.org/d/2424-psds-server/13). |