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improve information on PSDS

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Daniel Micay 2023-03-14 05:58:22 -04:00
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commit eaf29c2a5a
1 changed files with 28 additions and 20 deletions
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static/faq.html
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@ -834,12 +834,20 @@
servers. These contain orbits and statuses of satellites, Earth
environmental data and time adjustment information.</p>
<p>Qualcomm Snapdragon SoC devices also use the ntp.org NTP pool from
the GNSS location service implementation when it's enabled as part of
improving GNSS-based location accuracy. These connections are not used
to update the system clock. GrapheneOS will likely offer more control
over this in the future, although Pixels moving away from Snapdragon
has moved this onto the backburner.</p>
<p>On 6th and 7th generation Pixels (which use a Broadcom GNSS chip),
almanacs are downloaded from
https://broadcom.psds.grapheneos.org/lto2.dat,
https://broadcom.psds.grapheneos.org/rto.dat and
https://broadcom.psds.grapheneos.org/rtistatus.dat which are a cache
for Broadcom's data available at
https://gllto.glpals.com/7day/v5/latest/lto2.dat,
https://gllto.glpals.com/rto/v1/latest/rto.dat and
https://gllto.glpals.com/rtistatus4.dat. Alternatively, the standard
servers can be enabled in the Settings app which are
https://agnss.goog/lto2.dat, https://agnss.goog/rto.dat and
https://agnss.goog/rtistatus.dat providing a similar cache of
Broadcom's data currently (as of October 2022) hosted on GCP (Google
Cloud Platform).</p>
<p>On 4th and 5th generation Pixels (which use a Qualcomm baseband
providing cellular, Wi-Fi, Bluetooth and GNSS in separate sandboxes),
@ -855,20 +863,20 @@
retain the option to use the standard servers to blend in with other
devices.</p>
<p>On 6th and 7th generation Pixels (which use a Broadcom GNSS chip),
almanacs are downloaded from
https://broadcom.psds.grapheneos.org/lto2.dat,
https://broadcom.psds.grapheneos.org/rto.dat and
https://broadcom.psds.grapheneos.org/rtistatus.dat which are a cache
for Broadcom's data available at
https://gllto.glpals.com/7day/v5/latest/lto2.dat,
https://gllto.glpals.com/rto/v1/latest/rto.dat and
https://gllto.glpals.com/rtistatus4.dat. Alternatively, the standard
servers can be enabled in the Settings app which are
https://agnss.goog/lto2.dat, https://agnss.goog/rto.dat and
https://agnss.goog/rtistatus.dat providing a similar cache of
Broadcom's data currently (as of October 2022) hosted on GCP (Google
Cloud Platform).</p>
<p>Qualcomm Snapdragon SoC devices also fetch time from
time.xtracloud.net via NTP rather than using the OS time. Stock Pixel
OS overrides this to time.google.com but we use the standard server
like other Snapdragon devices. It's technically incorrect to use the
time.google.com server for this due to non-standard leap second
smearing not expected by the Qualcomm GNSS implementation. This could
be avoided by using OS time instead but Qualcomm built it this way to
avoid GNSS-based location being crippled by having time set wrong in
the OS.</p>
<p>We're hosting a similar PSDS cache for Qualcomm PSDS data and plan
to use it by default once we implement support for switching between
our servers and Qualcomm's servers via the same toggle we use for the
newer Broadcomm GNSS Pixels.</p>
</li>
<li>
<p>Connectivity checks designed to mimic a web browser user agent are performed