More on Geotagging

I posted recently about geotagging photos in Linux. There is a post on the digiKam blog about the same subject with a good idea I hadn’t thought off, using your Android (or any other one that can tag photos) phone to take a reference shot. Read the whole post here, it’s worth a look.


Geotagging in Linux

You may ask why geotag images? I have some images I took on film 20 years ago and would love to know where they were taken. Often I have a rough idea but I couldn’t find my way back there if I wanted too. One image is marked ‘beside the Croydon to Georgetown Road, Queensland’. Not very helpful when you think those 2 towns are nearly 150k apart, that’s almost 95 miles for those from non metric places.

Recently I’ve been experimenting with automatically geotagging my photos, also known as GPS Co-relating. This requires having a gps track of where I have been and an application that can match that track with the appropriate photos.

First thing is to create a gps track. This can be done with a dedicated gps unit or with some other device. I chose to use my android phone because I always have it with me. To record the track requires an app. There are many available but I use ‘Open GPS Tracker‘ because it is open source, it’s free and it works. It has many options that I don’t use including real time streaming. It has the option to output .gpx files which is what the co-relating applications require.

After you have the track you need an application to read it and match it to your photos. As always there are a number of options in Linux. Digikam has this option but I couldn’t get it to work reliably so I use ‘GPS Correlator’. It is available in the repos of many Linux distros, just needs a ‘yum install gpscorrelator’ in Kororaa (and Fedora). It has more options than Digikam which is how I got it working.

One thing I should mention is that your camera and gps unit (phone in my case) must have the time settings synchronised as accurately as  possible. Doesn’t need to be to the second but as close as you can get it. As most phones handle their time settings automatically this means changing the setting on your camera. Check it before each use particularly if you live in an area with daylight saving.

In the gpscorrelator screen you can select photos to process then the gpx file you got from your gps unit. You should set the time zone your camera is set to as gps data is always in UTC. You can also set the time difference and offset. Fortunately gpscorrelator has tool tips which describe how to use these options. If you still get no match on some images try selecting the ‘Between Segments’, it compensates for any gaps in your track. Particularly useful for areas with poor gps reception like cities and wooded areas.

Gpscorrelator also has an option to remove gps data from images if you want your location to remain private. This is handy for phones and other cameras that automatically record your location. For images taken at home and at friends’ places you might prefer to keep the location private when you post them on photo sharing sites.

There are a couple of things I’ve learnt so far. First is allow some time between starting the tracker and taking your first image. Also between taking the last image and stopping the tracker. First time I tried it I stopped the tracker when I got back in the car after taking the last images. None of the images taken there would match as the last point in the track was some time before the images were taken. Today when I got it working I started the tracker when I left home and stopped it when I get back.

Second is if you are constantly moving you might need to adjust the ‘Logging Precision’ in ‘Open GPS Tracker’s settings. It defaults to normal but if you find this doesn’t give enough points try a more precise setting or set you own custom interval. Experimenting is the only way to know what works for you. Explore the settings for other options that may improve your accuracy or that you might find useful too.

If you are using the tracker for a long period, e.g. most of the day, you might need to consider battery life. So far I’ve been in the car and I can plug the phone into a charger so that isn’t a problem. But without the external power recording a track for several hours may result in a dead phone battery. This maybe a good use for an old android phone if you have one laying around, maybe you know someone who has recently updated?

Adding location tags to your images is useful now and so easy to do why not try it.

It’s the Little Things

Most modern operating systems do a reasonable job and that applies even more to most current Linux distros. However it is often little things that bug users. These are issues that don’t stop you working but do get in your way a bit. I have a few and when there is a bit of free time I look for solutions. Recently I found answers to 2 of these problems.

The first is when viewing an image in full screen in digiKam the screen flashes. This seems to be a Kwin problem and I was pleased to find a fix. I didn’t record where I found this so apologies to the helpful person who made this public. It was necessary to run the following commands

kwriteconfig –file kwinrc –group Compositing –key UnredirectFullscreen –type bool false
qdbus org.kde.kwin /KWin reconfigure

The other issue was with suspend and resume. My laptop does both without error but the bluetooth service doesn’t restart at resume. That means no mouse, a situation which makes the computer unusable. It is possible to manually restart the service but that is a nuisance. So the solution is to add a script to restart the service. The details are found on the Fedora forum.

Fixing little things like this makes the system so much easier to live with.

Downloading Photos

I have recently been using the “RAW + jpg” setting on my Canon DSLR.  It is useful in some circumstances as it gives a jpg image that can be used immediately. If I’m not happy with the jpg or want to do some editing for any reason I use the RAW file. I find I only use the RAW about 10% of the time so it allows me to upload my photos much faster.

There is a couple of drawbacks. First it reduces the number of images that can be taken before the camera stops shooting and gives its busy message while it saves them. This is only an issue when in continuous mode. If shooting single shots it is fine.

The other issue is downloading the images to the computer. I use digiKam for photo management. I always rename the files as I download them from the “image_xxxx” format to something a little more meaningful, normally I use a “date-subject-num” format. When downloading with the default settings digiKam will number the cr2 raw file as 1 and the jpg as 2 etc. However I found a setting in the download options for numbers to use the extensions. This will give the cr2 and jpg the same number with only the extension to differentiate the 2 files. Exactly what I wanted. digiKam continues to amaze me with how powerful and useful it is.