[digiKam-users] Edit geolocation of pictures

[Martin Burnicki]

Sorry, I just came across this older message.

Remco Viëtor wrote:
> Not sure if this is any help, but I just got something similar. When I looked 
> at the gpx file (it's a simple XML format), the *dates* were wrong (don't ask 
> me how that happened, I have no idea). the *times* were correct... A simple 
> search&replace with the correct date fixed the problem.

This is due to a GPS week number rollover, which happened on April 6/7
this year.

Some GPS devices can't handle this correctly and step the time back by
1024 weeks, which results in a date in 1999. See:
https://kb.meinbergglobal.com/kb/time_sync/gnss_systems/gps_week_number_rollover

Other GPS receivers have implemented a very simple approach to "adjust"
the week number they receive from the satellites. This approach can fail
at any weekend, depending on the receiver and firmware. See:
https://kb.meinbergglobal.com/kb/time_sync/gnss_systems/gps_week_number_rollover#a_simple_error_prone_approach

I have an old GPS tracker, based on a MediaTek chip, which still outputs
the correct dat:
https://www.amazon.de/gp/product/B002V182KG

And I have another one which is newer, but fails and outputs the wrong
date now:
https://www.amazon.de/gp/product/B00I4Z1SQS

I use gpsbabel
https://github.com/gpsbabel/gpsbabel

on a Linux command line to retrieve the data from the GPS trackers and
store the tracks in GPX files. Current versions of gpsbabel provide a
command line option to shift the date saved in the gpx file by 1024
weeks (i.e., by 7168 days), so the dates in the gpx file are correct. See:
https://github.com/gpsbabel/gpsbabel/issues/349#issuecomment-526851146

Martin