GNSS Blackout in UrbanNav-HK-Medium-Urban-1
tipf opened this issue · 7 comments
Hi everyone,
there seems to be a GNSS blackout in the "20210517.light-urban.tste.ublox.f9p.obs" file of the "medium urban" dataset.
Exactly between:
> 2021 5 17 2 42 30.0050000 0 28
and
> 2021 5 17 2 44 41.0050000 0 29
During this period, no observation exists in the RINEX file.
Other files like "20210517.light-urban.tste.ublox.f9p.splitter.obs" or the m8t files do have observations in this period.
Is this a known property of the dataset or a problem in the post-processing?
Best Regard
Tim
Dear Tim,
Yes, some receivers cannot receive signals well in short period in urban canyons. You can try other sensors if you want to have continuous measurements, e.g, 20210517.light-urban.tste.ublox.f9p.splitter.obs which another F9P uses a geodetic antenna
Best Regards,
Darren
Dear Darren,
thanks for your fast response. I plotted the visibility of all satellites over time and there is a big gap of 120s.
I understand that such things can happen in urban canyons, but 120s while driving in a medium-urban environment?
Isn't it unlikely that all satellites drop out simultaneously?
I added furthermore a plot of the pseudorange residual over time. You can see the phenomenon there too, and there is no increase in the error before and after the blackout.
Could it be a receiver malfunction or a glitch in the data recording?
Dear Tim,
Yes, I think this F9P sensor very possibly has some receiver issues in these 120s. Let me involve one colleague which an expert in GNSS to help this issue @ivannhf
Best Regards,
Darren
Dear Tim,
Seems there is a malfunction on the receiver, could be a connection lost during that period.
We suggest avoiding that period or using another F9P receiver connect to a geodetic-grade antenna.
Best regards,
Ivan
Dear Darren and Ivan,
could you maybe add a note to inform potential users about that glitch?
(And can decide whether they want to avoid it or not.)
Best Regards
Tim
Dear Tim,
Thank you for your suggestion. Notification of this issue is added to the description of the medium urban. e6c236a
Best Regards,
Darren
Thanks a lot Darren!