Map module not finding photos from track log

Question

I have created GPX files on my phone, loaded them into the map module and selected the corresponding photos. When I select "Auto-tag selected photos" from the pop-up menu where I loaded the track I get an error saying "No Matching Photos" I have checked the track data and the times of the photos and they do match - the track runs from 12:32 to 4:37 on 9-13-2012 and the photos were all taken within this time frame. Any ideas what might be going wrong?

Answer 1

I had the same problem, and I've found the solution.
In short:
Lightroom expects that the times in a .GPX file are in GMT/UTC. It applies the time offset for your local computer to determine the time of the tracklog. As of Lightroom 4.2, it doesn't handle time offsets (as in "+1200") embedded in GPX files. For example, I shot photos recently using the (excellent) SkiRoute16 GPS logger app on my iPhone, then exported to a GPX file. Because London was in summer time, SkiRoute16 appended the offset to the locations:
</trkpt>
<trkpt lat="41.54921491494658" lon="-0.06738643106430209">
<time>2012-09-25T09:26:40+0100</time>
</trkpt>
How do I know if my GPX file has offsets embedded?
If you load a tracklog into the Map module and hover over the tracklog, you should see timestamp tooltips appear. If not, it's probably because there are offsets in the GPX file.
How do I fix it?
If your Lightroom PC, photos, and GPX file are all in the same timezone, then you should be able to simply remove the offset. A GPX file is just an XML file, so you can use Notepad, TextWrangler, or whatever to open it. Use find-and-replace to replace the offset with nothing. That is, replace "+0100" with "" - the <time> elements should now look like this:
     <time>2012-09-25T09:26:40</time>
Save the GPX file as a new file (don't overwrite the original, just in case things go wrong). Try loading it into Lightroom and see if it works.
If your Lightroom PC is in a different timezone to the GPX data
...Then you'll have do some additional fiddling after removing the offsets:
Find the time offset of your PC or Mac. For example, I'm in New Zealand and so my time offset right now is +1300.
Work out what offset to use. In my case, the pictures were taken around 9:30a.m:
     <time>2012-09-25T09:26:40</time>
Lightroom's going to assume this is GMT/UTC and add thirteen hours to this (because that's the time offset of my laptop).
This means I need to subtract 13 hours, which will actually takes the timestamps back to the previous day. 9am on 25 October needs to become 8pm on 24 October:
     <time>2012-09-25T09:26:40</time>
Needs to become:
     <time>2012-09-24T20:26:40</time>
First, I'll change the day by doing a find-and-replace on "2012-09-25" and replace it with "2012-09-24":
     <time>2012-09-25T09:26:40</time>
Becomes:
     <time>2012-09-24T09:26:40</time>
Now, I replace the time portion, again using find-and-replace to replace "T09" with "T20":
     <time>2012-09-25T09:26:40</time>
Becomes thirteen hours earlier:
     <time>2012-09-24T20:26:40</time>
Once this is done, save the file (again, save as a different filename. Playing with these offsets took me several attempts, and you don't want to overwrite your original GPX file). Then try re-importing the tracklog and see how you go.
Phew!