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Stan
I've been having a problem geocoding NEF raw images from a recent trip, and I believe the problem is to do with timezone mismatch, but I just can't solve it.

1) Camera accidentally left on GMT+1 timezone (British Summer Time).
2) GPX tracklog downloaded from GPS ok; times appear to be in GMT as expected.
3) Used Lightroom 2 to adjust date/time to local time of each photo (GMT-3 or GMT-2).
4) Tried to geocode using HG...no coordinates assigned to photos.

I tried step 4 using various timezones, but nothing. I believe the key problem maybe the adjustment step 3, which has created an information anomaly.
Various data for an example image are shown below. Any ideas why this might be? Does HG get confused if the date/time info from the image and XMP don't agree?

Stan


Raw NEF file shows (using exiftool):
---- IFD0 ----
Modify Date                     : 2010:06:18 20:25:19
Date/Time Original              : 2010:06:18 20:25:19
---- ExifIFD ----
Date/Time Original              : 2010:06:18 20:25:19
Create Date                     : 2010:06:18 20:25:19
---- Composite ----
Create Date                     : 2010:06:18 20:25:19.43
Date/Time Original              : 2010:06:18 20:25:19.43
Modify Date                     : 2010:06:18 20:25:19.43


LR shows for same image: 18/06/2010 17:25:14


XMP sidecar shows:

 <exifateTimeOriginal>2010-06-18T17:25:14+01:00</exifateTimeOriginal>
<exifateTimeDigitized>2010-06-18T17:25:14+01:00</exifateTimeDigitized>

<xap:ModifyDate>2010-06-18T17:25:14+01:00</xap:ModifyDate>
<xap:CreateDate>2010-06-18T17:25:14+01:00</xap:CreateDate>

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houdah
Hi!

When present, HoudahGeo reads metadata from the XMP sidecar.

Dates and times in HoudahGeo are displayed using the time zone set using the pop-up menu in the top right corner. This setting applies to the document window as well as the track log inspector. You may thus compare the timestamps in the document window to the time spans in the track log inspector to see if the images fall within the time spans covered by track logs.

Hope this helps. If not, email me a sample sidecar as well as the track log.

Best,
Pierre Bernard
Houdah Software s.à r.l.

Houdah Software s. à r. l.
https://www.houdah.com

HoudahGeo: One-stop photo geocoding
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Stan
Hi Pierre, thanks for getting back to me so soon. So I've managed to get it working now, but I don't completely feel as though I understand the logic behind the process.

Q: What's the link between the camera timezone in Camera Setup, and the timezone at the top-right?

I got it working using a camera timezone of GMT-2, a clock error of -10800 (3 hours forward), and a timezone in the top-right of GMT. My logic was that the tracklog is in GMT, so top-right=GMT. What about the camera timezone setting? Why didn't this realign the photos' times to GMT, and why did I need the offset?

I can't find definitive documentation on how the various timezone settings should work, and from the forums it seems many other people have similar problems. It would make sense to write an short article explaining the exact function of each time-related option, including the effects it has (i.e. images, tracks, etc.). I got it working, but I'm still confused as to how I should configure it for future operation.

Thanks,
Stan
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houdah
Hi!

GPS devices get their time information from the satellites. It is always accurate and always stored with a GMT time zone.

Camera clocks are not always accurate and usually don't know what time zone they have been set to. They write a timestamp without time zone information.

In order to properly interpret the photo timestamps and to match them up with GPS data, HoudahGeo needs to know which time zone the camera was set to. BTW, I strongly recommend against abusing the "clock error" setting to compensate for a time zone error.

The menu in the top right corner just switches the way the timestamps are displayed. This has no influence on the actual process of geocoding. Some people like to think of all times being GMT, others want to see the exact times their camera displayed, still others want the computer time zone to be used.

Best,
Pierre Bernard
Houdah Software s.à r.l.

Houdah Software s. à r. l.
https://www.houdah.com

HoudahGeo: One-stop photo geocoding
HoudahSpot: Advanced file search utility
Tembo: Easy and effective file search
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Stan
Thanks, although I already know about GPS recording in GMT, and camera needing to have timezone specified. What I'm misunderstanding is why I also need to provide an offset to get the correct time association with HG.

As far I can understand:

1) The top-right drop-down is essentially irrelevant, but just determines what time is displayed (i.e. doesn't affect time associations).
2) "Camera timezone" is used to adjust the photos to align with the tracklog.
3) "Clock error" is used to fix small (e.g. seconds) camera time errors.

As my photos now have the correct local time, I should be able to just use the camera timezone set to GMT-2, which is the timezone in which the photos were taken, and what they were assigned to in Lightroom. However, this doesn't work; no geocoding happens, or what does is assigned from the wrong part of the tracklog. I had to use "clock error" to get the times aligned correctly, which makes no sense to me. The correct tracklog point for this photo is listed as:
2010-06-18T19:25:14Z
which means that the GMT-2 camera timezone should have worked, but it didn't. This indicates some problem to me, which I can't identify.

The urgency is off now for me, as I've geocoded using the offset technique, but it leaves me with a sense of unpredictability about the software. When it works it's great, but it takes trial and error to make it work.

Stan

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houdah
Hi!

You are correct on all accounts.

There is one detail, I forgot to mention. If the camera does specify a time zone, that takes precedence over the setting you make in HoudahGeo.

Your camera did not, but Lightroom did: 2010-06-18T17:25:14+01:00
This is set to GMT+1. I.e. This timestamp can be read as 16:25 GMT, 3 hours off from where you want it to be.

That error can indeed only be corrected using the clock error setting. More important however is to find out where it has been introduced.

Best,
Pierre Bernard
Houdah Software s.à r.l.

Houdah Software s. à r. l.
https://www.houdah.com

HoudahGeo: One-stop photo geocoding
HoudahSpot: Advanced file search utility
Tembo: Easy and effective file search
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Stan
Ok, so LR still thinks the photos are in GMT+1, which is not what I wanted. The time I want is
2010-06-18T17:25:14-02:00
which represents the actual time I took the photo. How I get to this I have no idea, without resorting to command-line use of exiftool. Anyhow, what you're saying seems to solve the mystery, as using "camera timezone" there is no way to realign the times, because it's overridden by LR, so I must use "clock error" to fix this. Hmmm...now to find a convenient way to correct the time properly for ~700 photos in two timezones.

Thanks, Stan
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houdah
Hi!

You may use HoudahGeo's "clock error" to fix timestamps.

If I remember correctly, you will need to set "camera time zone" to the time zone you want to be written to the file and then set clock error accordingly. This is tricky business. Please try on a sample file first.

Time shifting using exifTool is probably much easier. That would be a matter of issuing commands like:
[CODE]exiftool "-DateTimeOriginal+=0:0:0 3:0:0" file_or_directory[/CODE]
Again: try on a sample file to see if you get the desired result.

Best,
Pierre Bernard
Houdah Software s.à r.l.

Houdah Software s. à r. l.
https://www.houdah.com

HoudahGeo: One-stop photo geocoding
HoudahSpot: Advanced file search utility
Tembo: Easy and effective file search
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