Opened 6 weeks ago

Closed 3 weeks ago

Last modified 3 weeks ago

#17576 closed defect (fixed)

[Patch] Fix timezones and DST for image correlation

Reported by: Bjoeni Owned by: team
Priority: normal Milestone: 19.05
Component: Core image mapping Version:
Keywords: Cc: Don-vip, simon04


Not sure if it was a defect, but certainly very unexpected behavior for me.

I'd expect the timezones set in the dialog to be absolute, so if the GPS track is ZULU, I'm currently in Germany (UTC+2) and I'm geotagging images taken in Thailand (UTC+7), I should set the timezone to "+7:00" (that's why it's called 'timezone' and not 'offset').

However at the moment it is indeed depending on the timezone you are in, so when I tried to correlate the images from Thailand while being in Germany, I had to use "-5:00" as a timezone, whereas the same task in New Zealand would require the timezone to be "+6:00".
This is because the EXIF usually doesn't contain timezone data and the EXIF reader applies the current timezone, which leads to the same picture once being i.e. 13:00 NZST and once 13:00 CEST (which is obviously very different).

The patch fixes this by completely ignoring the local timezone when reading EXIF data (assuming ZULU) and only using the local timezone as default when prefilling the textbox.
It also allows the user to activate/deactivate daylight saving time when synchronizing from a photo (separate enhancement). This currently leads to an offset of 3600 secs which doesn't really seem to make much sense either.

Attachments (3)

17576-timezones.diff (9.2 KB) - added by Bjoeni 6 weeks ago.
synchronizedialog.png (192.2 KB) - added by Bjoeni 5 weeks ago.
17576-timezones-V2.diff (12.9 KB) - added by Bjoeni 5 weeks ago.

Download all attachments as: .zip

Change History (8)

Changed 6 weeks ago by Bjoeni

Attachment: 17576-timezones.diff added

Changed 5 weeks ago by Bjoeni

Attachment: synchronizedialog.png added

Changed 5 weeks ago by Bjoeni

Attachment: 17576-timezones-V2.diff added

comment:1 Changed 5 weeks ago by Bjoeni

Just noticed that apparently I didn't upload the latest version of the patch. Uploaded it now as V2.

comment:2 Changed 5 weeks ago by Bjoeni

And btw. this might actually be a regression of [14079]. Before, GPX trackpoints and Photos were both (wrongly) assumed to be in the local timezone, currently GPX is in UTC and Photos are in the local timezone.

comment:3 Changed 4 weeks ago by Don-vip

Milestone: 19.05

comment:4 Changed 3 weeks ago by Don-vip

Resolution: fixed
Status: newclosed

In 15045/josm:

fix #17576 - Fix timezones and DST for image correlation (patch by Bjoeni, modified)

comment:5 Changed 3 weeks ago by Don-vip

In 15047/josm:

see #17576 - update ExifReaderTest

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