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.

Navigation With Android

I have been using an Android phone for a while now but haven’t blogged about it before. Not for any negative reason but simply because I had little to say. I bought a HTC Hero outright, no contract. I love it, it works well and does everything I wanted and much more. It came with Android 1.6 but soon after I got it an "Over the Air" update from HTC upgraded it to 2.1. That went well and added several features and a few bug fixes.

I had read that the latest update to Google Maps added a Navigation feature so I decided to test it today. I wasn’t going very far and it was a route I often take which I think is a good way to test. I wanted to see if it would replace my Tom Tom GPS. One less gadget in the car is a good thing. The phone is mounted in a cradle that mounts to the windscreen with a suctionn cap just like a GPS so it should receive the GPS signal well.

There is a navigation icon on the applications screen and that immediately asked me to activate GPS. Which I did. I tried to type in a destination but the hint list only showed US and UK locations so I changed to Spoken commands which worked surprisingly well when I gave the suburb and state it immediately found it as an Australian place.

When I asked for spoken directions I had to install the Text to Speech app. It worked well but defaulted to US English. It worked well but had trouble with several place names and couldn’t even pronounce "Way" as a road name. I have since changed it to UK to see if that is better.

The GPS worked quite quickly finding the location. Much better than the Tom Tom does when it hasn’t been used for a while. But I’m guessing it uses the phone location to get a start. It found almost the right place but where I was was difficult. It was the side street that runs beside a main road with only a few metres between them. It thought I was on the main road. Once I was moving it quickly zeroed in on the correct place. The directions were clear, allowing for the pronounciation problems, and accurate. It quickly recalcualted when I took a side street too.

So does it replace the dedicated device? I have some reservations and they are not really due to the app. The most biggest concern is the amount of download data needed. If you have a generous plan with plenty of data that won’t worry you but my plan only includes a couple hundred megabytes a month. If I were using it as a navigation device regularly that would be used up and I would be into the very expensive excess data. I could increase the data allowance by paying a small extra amount but the cost would exceed the cost of updates for my Tom Tom. So the conclusion is at the moment I think I would stick to using the Tom Tom when I am doing longer trips but for occasional help and as a backup the phone is great. If I didn’t already own a GPS unit I wouldn’t buy one I would use the phone without hesitation.

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