Geotagging problem

Hello my friends!

Recently I've made an air trip from Newark to Las Vegas. During the flight we had a lot of fun and took many pictures, including some amazing shots of the Grand Canyon from the top. Since I always keep my photos organized, when I came home I was correcting the Time field in the EXIF of my photos. The photos from Vegas were easy to ajust - just had to subtract 3 hours. But...

During the flight, we passed trough many time zones (Eastern, Central, Mountain and Pacific, that are the time zones they have in USA). So, here comes the problem: if I correct the time zone of each photo based on where we were, the photos will not be anymore in the sequence they were shot. How can I keep Time acurate without messing the real sequence of the photos?

Example: "Photo 1" was taken when we departure, at 6pm. 50 minutes latter we changed from Eastern Time to Central Time (minus 1 hour) and I took "Photo 2". If I ajust time in Photo 2 to make it acurate, it will show a time stamp of 5:50pm, and it will look like it was taken prior to Photo 1.

PS: Many programs like Adobe Photoshop Elements uses the EXIF's Time stamp to order the photos, that's why I'm concerned they will show out of order.

Any hint will be greatfully appreciated, specially if someone has been trough the same situation.

Best regards,
Luis Eugenio

Don't organize the photos by date/time.

Organize them by the number of the image assigned by the camera

Luis Eugenio said:

Any hint will be greatfully appreciated, specially if someone has been trough the same situation.

Click to expand...

I always keep the camera set for local time or GMT. I see no reason to adjust for local time.

BTW, how is this a "geotagging problem"?
--
-Dave
http://pixseal.com

pixseal said:

BTW, how is this a "geotagging problem"?
--
-Dave
http://pixseal.com

Click to expand...

Hi Dave!

Actually the problem started when I was geotagging my photos with GeoSetter. I had to set time right to be able to sync my AMOD log with the photos. Just then I realized that if I did corrected the time, the photos would be out of sequence.

But you are right, the way I exposed the problem doesn't necessarily means it a geotagging problem, it's more like "time zone problem".

But I'm sure other people have been trough something similar... I'm just curious on how you deal with this situation.

If I don't do anything, the photos would show that I arrived in Vegas at 10pm, when it actually was 7pm and still sunny. Also, then I'll have a geotagging problem, since AMOD would log with the correct time and the photos would be shifted.

Thanks for your suggestions so far.

Best regards,
Luis Eugenio

Several elements conspire against a photographer who travels:

1) image metadata does not, as a rule, include time zone information.

2) few cameras keep in their system anything other than zone-unspecified "time/date" information.

3) even when they provide something like "home-time/date and "travel time/date" it isn't always obvious how is that information included in the image header data.

Given the above, most photographers that travel keep camera time on UTC ("Zulu time", "World time", GMT, whatever else it may be called...). Since GPS unit trace times are (for all GPS devices I've seen) invariable UTC, this is least likely to result in any problems for deriving locations of photograps from time match between camera time and GPS trace times, and will keep the camera assigned file name sequence the same as the image time/date information, no matter in which direction (East or WesT) or how fast one moves. The only time one needs to actually correct the camera time due to travel is when one crosses the International Date Line.

Unfortunately, camera time-keeping electronics is notoriously inaccurate. Instead of adjusting the seconds and minutes of camera clock with anoying regularity, one can simply take, as the first photo of a new day, a picture of a gps display with time (including seconds!) page. If one's wrist watch (for those of us that still use such device is of decent quality and kept within a second or so of true time, a photo of it might be just as usefull, and may be the only alternative if we use display-less GPS logger. The difference between time read from the image header data and displayed by software and time read from the image itself can then be entered into the location software as a time "correction" or "differential".

Teron

teron said:

Given the above, most photographers that travel keep camera time on UTC ("Zulu time", "World time", GMT, whatever else it may be called...). Since GPS unit trace times are (for all GPS devices I've seen) invariable UTC, this is least likely to result in any problems for deriving locations of photograps from time match between camera time and GPS trace times, and will keep the camera assigned file name sequence the same as the image time/date information, no matter in which direction (East or West) or how fast one moves. The only time one needs to actually correct the camera time due to travel is when one crosses the International Date Line.

Click to expand...

(good explanation of the benefits of setting the camera to Zulu time)

I always keep my camera on local time for these benefits:

• I like my images tagged for the correct day
• My Garmin GPSMAP 76CSx breaks the track log into daily files, named for the local day. (Within the files are Zulu time stamps with Zulu date)
• My trips so far have all been within 4 timezones of home (Zulu -7/8)

Since I never travel overnight, this has a good organizational benefit. However, I never change my camera clock while traveling.

• Would consider changing the camera "local" time for the entire trip if I was to travel 6+ timezones away.

I’m curious; if you keep your camera on Zulu time, why would crossing the date-line matter?
--
-Dave
http://pixseal.com

dherzstein said:

• My Garmin GPSMAP 76CSx breaks the track log into daily files, named for the local day. (Within the files are Zulu time stamps with Zulu date)

Click to expand...

I should have mentioned that my GPSr allows me to specify the local time. Of course the GPX track log file contains only Zulu, but the local time defines how the GPX files are labled and how the time is displayed on the GPSr screen.
--
-Dave
http://pixseal.com

dherzstein said:

I’m curious; if you keep your camera on Zulu time, why would crossing the date-line matter?

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The camera time-piece keeps both time-of-day and the day. When you cross the date line the UTC time-of-day does not change, but the date does - thats why "we invented it", thats where a new day begins and starts its daily march with Sun, from East to West, until it hits the date line and is no more, anywhere on Earth.

Imagine you are just a short distance west of the line and it is a noon on August 29th. Now move (very fast) some distance East, across the line. It is still (more or less) noon, but you are in the "previous day": it will take 24 hours for the noon Sun "of date August 29" to travel around the world and reach you. I imagine a GPS unit will know that you crossed the line and will change the date by itself (anybody out there reading this in the departure lounge in Sydney, ready to board that non-stop AC Vancouver flight? Could you plase let us know But the camera time-piece has no idea it crossed the date line: it must have its date decremented "by hand".

(and of course, the other way round, if you travel West).

Teron

teron said:

dherzstein said:

I’m curious; if you keep your camera on Zulu time, why would crossing the date-line matter?

Click to expand...

The camera time-piece keeps both time-of-day and the day. When you cross the date line the UTC time-of-day does not change, but the date does....

Click to expand...

No, it doesn't. The LOCAL time and date depend on your location, but UTC doesn't care where you are. A way to picture this is to imagine UTC as the local time and date in London during the season when you paddle your canoe over the dateline out in the Pacific Ocean. You have your camera with you and it is set to London's time and date: UTC. As you paddle your canoe across the dateline, yes, your local Pacific Ocean time zone changes date, but your camera isn't set to the local date. It's set to the date in London, which doesn't depend on you in any way. As you paddle across the dateline, the date doesn't change in London, so neither should it on your camera if you have it set to London Time (UTC).

That's why UTC is so useful. If you set the date and time correctly in any location, they will remain correct---both time and date---in all locations.