Blog entries tagged with "geotagging"

GPS Week Number Rollover

Saturday, July 27th, 2019 at 7:42 pm

A quirk of the GPS system is that it uses a week counter to represent the date, this can only represent a maximum of 1024 weeks, so every ~19.7 years it resets to zero, known at the GPS Week Number Rollover.

The second rollover was earlier this year and there was plenty of media coverage as well as government statement at the time. I also saw a number of YouTube videos about it, such as this one from Matt Parker:

The handheld GPS unit I use for geotagging photos is from Garmin, so I was particularly interested in what they had to say about it. Well that is non-specific… is my device (obtained second hand twelve years ago and last firmware update was ten years ago) part of the “vast majority” that “will handle the WNRO without issues”?

I wasn’t that concerned so opted for a wait and see approach, so when I used it in late April I was pleased to see that it was logging the correct date. However when I used it in May and June I noticed that there would be spurious log files, as if it was starting up with the wrong date and then adjusting to be correct.

Today was my first time heading out to take photos since June, so I was disappointed to find that my GPS device is now stuck in 1999. The location and time are correct, just the date is wrong.

When geotagging my photos from the GPS track I would specify the time offset between the camera (local time of where I was) and UTC, so for Melbourne at UTC+10 that is an offset of -36000 seconds. Since the date it is logging is now 1024 weeks out, I could specify an additional offset of -619315200 seconds…

The more reasonable option is to look for a new GPS unit, but with my key requirements of AA (or AAA batteries) and a GPX file written to an SD card I suspect that I might just end up with a newer version of what I have. I have seen some nice small dedicated GPS logging devices, but I want to be able to easily swap in fresh batteries or don’t want to be forced to use their software to access the tracks.

I had a quick look at eBay to get an idea of what might be available, saw plenty of devices like what I already have, but don’t see any mention of GPS Week Number Rollover in the item descriptions…

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My travel photo workflow

Tuesday, February 5th, 2019 at 9:28 pm

I’ve been sitting on this post for a while (first started while in San Francisco) so my trip around the South island of New Zealand is a good time to get it finished. Upon reflection it is pretty much the same…


  • Camera – of course
  • GPS – I have a Garmin eTrex Vista HCx that is intended for bushwalking, but I just use it to log
  • Computer – A small windows laptop with Lightroom and other tools

During the day:

  • Take photos, lots of them
  • Have the GPS on and always keep it near the camera
  • Take a photo of the GPS device showing the current time

Each night:

1. Copy photos and GPS track

Once I am settled down for the day and have the laptop out I start to copy the photos from my Compact Flash card (or cards if a big day) into an ‘incoming’ directory.

As copying the photos can take a while (though not as long now I used a USB3 card reader) I leave that running and copy the GPS tracks (in GPX files) from my GPS device. I used to to put my GPS device in mass storage mode to access the microSD card via a USB cable, but these days I pull out the microSD card and put it into the card reader.

2. Check GPS track and photo times

I rarely find errors in the GPS track (mostly in areas with lots of tall office buildings, or long periods indoors) but I still check it at this point by loading the GPS track into Google Earth. This does require an internet connection, but gives a nice overview of the day, possibly highlighting if I missed a location.

The photos should have completed copying, so I locate the photo of the time so I can confirm that the camera time is the same as GPS time. If I am careful when setting the time on the camera it can be within a few seconds of the GPS time, but if more than that I will use exiftool to adjust all the times of the photos so they match the GPS time.

3. Geotag photos

With the photos and tracks on the laptop I now use a command line tool called for most of my geotagging. This tool doesn’t appear to be maintained anymore, but it works for me. When I run it I specify the directory with GPS tracks, the directory with the photos, and the offset in seconds between the time of the photos and UTC.

4. Check tagged photos

If the GPS track is clean then typically all the photos will be correctly geotagged, but to allow for missing sections or errors in the track I check using another tool, this time a GUI tool called GeoSetter. I believe I can use this instead of to tag based on GPX files, but my current method works, and it looks like GeoSetter might also no longer be supported…

In GeoSetter I am mainly checking the location of all the photos against the map (fixing if required), and then manually adding location to photos if needed.

5. Import into Lightroom

Up to this point I have been directly updating the metadata of the photos, I want it to be correct at the source. While you can update the time and location in Lightroom, I’m not confident that the original file will be updated, not just in the Lightroom catalogue.

While I say “import” here, I’m not using the Lightroom import functionality. Instead I:

  1. run a script to rename the photos in the ‘incoming’ directory to a date based (the corrected GPS date) directory and filename. eg ‘incoming/IMG0349.CR2′ to ‘lightroom\todo\2019\2019-01-30\20190130T092158101-0349.CR2′
  2. within Lightroom right click on the ‘todo’ folder and use ‘Synchronize Folder…’ to find the new photos

I give the photos a quick check to see that the photos I expect from the day are now included in the Lightroom catalog and nothing is obviously wrong (eg corrupted).

6. Backup

Now that the photos have been added, I exit Lightroom and run a backup. This is nothing special, just robocopy to mirror the Lightroom catalog file and the photos to an external SSD.

7. Clear cards

Once the backup is complete I know that the photos exist in two locations (the internal drive of the laptop as well as the external backup SSD) I can clear the cards ready for the next day. I do this by formatting them in the camera.

8. The first cull

I will try to make at least one pass through the photos from the day using the Pick and Rejected flags in Lightroom. Mostly I will use the Rejected flag on any obviously bad (out of focus, undesired movement) or excessively duplicated (a couple of identical images are ok, but I don’t need a dozen) photos, but I occasionally Pick an image that I will definitely do something with.

Once this first pass is complete I will now delete all the Rejected photos, the CTRL+Backspace shortcut is very handy for this. I have found that I take a lot of photos during the day, and will cull around a third in this first pass…

Further processing

Depending on how long this has taken and the time I have available, I will keep going through the photos, rejecting some more but now starting to play around with some adjustments. While I save the bulk of the post-processing until I get home (on a more powerful computer with a much better screen) it is good to get started on it right away.

In fact I have set myself a goal on this trip to edit and post one image from each day, I’m trying to break my past habit of taking months (or years) to do something with the photos.

Back home

Unfortunately every trip comes to an end, for my workflow that means incorporating all the new photos into my existing library. I don’t try copying them from the laptop directly, instead I ensure that everything is synced to the external SSD, so I plug that into my desktop for the copy.

To simplify merging the two Lightroom catalogs I use the same directory structure for the photos on both computers, so they are copied directly over. I then open my main catalog and import from the copy of the laptop’s catalog. So far this has worked nicely, the photos are now incorporated in the main catalog along with any edits or flags that I made while travelling.

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Geotagging my photos

Sunday, July 26th, 2009 at 2:05 pm

For a long time now I have been using the map within Flickr to locate the photos that I have uploaded.

Since I bought a GPS unit I have taken it on long rides as well as some other journeys to allow me to follow a route and to track where I have been.

In the back of my mind I was aware that you can add GPS information to the EXIF data of images, but it wasn’t until a talk and presentation on geotagging last Tuesday at the camera club that I finally put them together for geotagging.

So, from this point on, I am going to attempt to geotag as many of my photos as I can where the location is appropriate (eg it isn’t for model shots of lego). For photo walks or camera club outings this means that I will have my GPS unit in the top of my camera bag. While for events such as Web Standards Group which is at a fixed location, I will add the location of the venue to the EXIF data instead of just in Flickr.

So how do I actually add the location?

I already use exiftool to sort my images into date based directories and to shift the dates if needed, so one initial thought was to write my own program.

No, first I would see what free programs were available. So over the past few days I have been looking at the first few programs I found: GPicSync, Geotag and PhotoMapper. I also came across which I will keep in mind if I write my own program as it is in perl, but I’m not looking at a command line tool yet.

  • GPicSync worked, but was slow and didn’t give a preview before writing to the files and generating a KML file
  • Geotag was fast and allowed me to preview before writing to the files. It also allowed me to tweak the time offset of the photos within the program, but I would still prefer to sync the files with GPS time first.
  • PhotoMapper was also fast and it provides a preview using Google Maps within the program before modifying the files. Unfortunately it only appears to support JPG, I also need support for RAW files.

I will keep looking at different programs until I am clear on how to fit geotagging into my workflow and which program will best do that.

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