Re: Time synchronization [was: GPS geotagging: first steps to implementation]

[Jan Girlich <vollkorn cryptobitch de>]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Am 06.09.2010 21:00, schrieb Michael Lissner:
>  This /is/ a really interesting train of thought, and as somebody that has spent
> days (literally), trying to correctly adjust times on my camera, it's very
> compelling to me. I worry though that the learning curve is too steep.

That's right. But that's also true for processing RAW pictures, but some
people want it ;) I think implementing it as an extension is the way to
go so people who want it can actively choose to use it.

Also, a good explanation for the user might be helpful. I imagine
- - a good helpfile
- - a wizard-like guidance for the first couple of times

> I'm not sure people will understand why taking a picture of their computer would
> somehow affect the timestamps on their photos, especially if they were taking a
> picture of a barcode.

As I said above, let's make it a pro-user extension then.

> Maybe a thing that would make it more obvious would be to
> have a screen where half of the picture was the current time (something that
> makes sense to humans), and the other half was the barcode (for the computers).

That's a good idea, but there is no need to sacrifice half the screen.
Most 2D barcodes are usually square, so you have about 1/4 of the screen
free anyway. Vertically, though, but big enough to show an help text and
the encoded time.

> I'm also concerned that I wouldn't use the feature because I wouldn't expect to
> have my computer near me when I remembered to set the time on my camera, so
> maybe a matching iPhone/Android app should be made?

Well, I used a prototype (doesn't work with the 0.6.x line anymore) for
a while and got used to it really quickly. And seriously: Never ever
change your cameras timesetting at all. Leave it at UTC for every summer
savings period or time zone. Local times should be derived from your GPS
positions automatically. Saves you a lot of trouble.

I really like the idea of an app so you can take a time correction
picture where ever and whenver you want!

> Another question I /know/ I'd have if I used this feature would be how the time
> zone setting on my computer/phone would affect the time stamp on the
> camera/photos.

Not at all. How could it possibly do so?

> I'm not an expert on EXIF, so I don't know whether JPEGs,
> cameras, f-spot, nautilus, etc. support it, so I'd be worried that would be
> messed up somehow. Again, maybe showing the time zone on the barcode screen (if
> it's encoded) would make sense?

You won't use timezones. This whole thing should only work in UTC to
avoid tons of hassle. The local times should be derived in a second
step, after the time correction, from the UTC times, the GPS data and a
database with the time zones and summer saving times. Those information
are freely available in the internet.

The EXIF part is no problem. All you do is reading and writing the time
in the header.

> A mock up or sketch of how this would look would make things gel much more, I
> think, though I'm terrible at making these things. I'll bounce this off some
> people, and see if anybody has any ideas...

I'll create a mockup. And some flowchart or similar to better explain
how I imagine this to work.

Cheers
Jan
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.10 (GNU/Linux)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/
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=AiT7
-----END PGP SIGNATURE-----