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-   -   N900 and GPS epoc rollover (https://talk.maemo.org/showthread.php?t=100665)

jonwil 2019-02-14 08:48
N900 and GPS epoc rollover
 
Does anyone know if this GPS rollover problem
https://www.theregister.co.uk/2019/0...ps_epoch_ends/
is going to cause issues for the N900 GPS?

nieldk 2019-02-14 09:04
Re: N900 and GPS epoc rollover
 
Probably, it seems devices released before ~2010 will almost certainly be affected.
Quote:
receivers that follow the ICD-200/IS-GPS-200 specification should be able to deal with the week number overflow. This basically means newer receivers built after, say, 2010 should be fine, provided they follow the specs and notice the rollover.

peterleinchen 2019-02-14 10:47
Re: N900 and GPS epoc rollover
 
Hard to say.without anyone knowing I would say.
It could be or it could not be.

Quote:
...
Additionally, some manufacturer implementationsinterpret the WN parameter relative to a date other than January 5, 1980. These devices should not beaffected by the WN rollover on April 6, 2019 but may experience a similar rollover event at a future date.For example, a particular GPS device may interpret the WN parameter relative to a firmware creationdate and would experience a similar rollover event 1024 weeks after that firmware creation date.
https://ics-cert.us-cert.gov/sites/d...n_GPS_2019.pdf

Furthermore in the ICD200-C from 2000 this rollover is already mentioned.
https://www.gps.gov/technical/icwg/


So also devices built before 2010 could already handle this correctly, or?

But I guess we just have to wait and see...

epninety 2019-02-14 11:41
Re: N900 and GPS epoc rollover
 
When the last rollover occurred (1999?) GPS units were rather less common than today, but there were a few where I worked for surveying and laboratory timing.
As I recall, units fell into 3 categories :-
1) No effect, continue operation as normal
2) Loss or degradation of time signal (and therefore probably position) until the ephemeris data downloaded from the satellites is all updated. This takes some minutes.
3) Total failure

I only saw one unit which was affected, and that was total failure. The assumption was that the firmware rejected satellite data claiming to be timestamped before the firmware build date. I don't recall the type, but it was an old unit even then.

I suspect the number of unit types which fail this time around will be very small.

sbk510 2021-09-12 15:28
Re: N900 and GPS epoc rollover
 
I often used GPS recorder since 2013 until the SUPL problem occurred. Now I have fixed this, but temporarily by set settings - location on supl.vodafone.com, this is at least not Google :) But now the next problem. GPS recorder sets the system date at GPS fix incorrectly, today to 2002-01-27 (GPS rollover). I can correct this manually, but in the recorded track are still the wrong date for begin, end, break, etc. GPSData also shows the wrong date, but does not change the system date. Mappero shows no date, but the wrong time, 1 h difference between summer time and winter time. In a recorded track the wrong date is stored. I could not find the dependencies for GPSData, but mappero and gpsrecorder use liblocation0, so I think that the reason can be found there. On my N900 liblocation0 0.102-1+0m5 is installed, it seems to be the latest version. Who can fix this? Should be possible by comparing the GPS date with the system time to determine the correct epoch.

Halftux 2021-09-26 00:54
Re: N900 and GPS epoc rollover
 
You could use gpscon to record a track as gpx. There is a date shift option.

sbk510 2022-10-25 10:48
Re: N900 and GPS epoc rollover
 
Simple fix if anybody needs this:

startgpsrecorder.sh
Code:
#!/bin/sh
lYMD=`date '+%Y.%m.%d'`
/usr/bin/gpsrecorder &
while true; do
        sleep 3
        YMD=`date '+%Y.%m.%d'`
        HMS=`date '+%H:%M:%S'`
        echo $YMD $HMS
        if [ "$lYMD" != "$YMD" ]; then
                sudo date -s "$lYMD-$lHMS"
                break
        fi
        lYMD=$YMD
        lHMS=$HMS
done
date '+%Y.%m.%d - %H:%M:%S'
add in /etc/sudoers
user ALL = NOPASSWD: /bin/date

in /usr/share/applications/hildon/ create a file gpsrecorder2.desktop
Code:
[Desktop Entry]
Type=Application
Terminal=true
Name=GPS Recorder2
Exec=/home/user/startgpsrecorder.sh
Icon=gpsrecorder
Now there should be an entry GPS Recorder2 and you can create an icon.


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