Leon Steenkamp
Building small satellites on the tip of Africa. My other ride is a CubeSat.
Open water swim tracker - final swim and conclusion
This post is the final post in a series detailing the Open water swim tracker project - more info here.
The False Bay crossing mentioned in the previous post was the biggest test for the tracker hardware up to this point.
The initial idea was to use the tracker hardware on an even bigger swim - an English Channel crossing. Other options for following swimmers across the Channel exist, but I wanted to have my own page, visualising my own data.
I wanted to explore other connectivity options, but Paula was going to attempt a Channel crossing in August 2025, and time was running out to evaluate other hardware options. My main concern was LTE connectivity. There would be no time to evaluate network provider options, and I did not feel like messing around with SIM cards on arrival.
Satellite-based connectivity solutions were briefly considered, which would have been great. These included Garmin’s InTouch, Iridium, and the Kinéis/Argos constellation, but these were either expensive in terms of hardware and subscription cost or it looked like they were not really geared towards consumer use.
To be frank, I also realised that I did not fancy trying to fly internationally with my tracker box.
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| The tracker hardware inside enclosure |
Another option was to write a mobile phone application. A mobile phone includes all the needed functionality; you would still have to deal with a SIM card, but the pain would be much, much less. It would also be easy to hotspot between phones, if needed. The phone app could generate the same message format as the original tracker hardware, so the backend software could be reused without any changes.
I’ve never written a phone app.
I had an old iPhone and always wanted to try my hand at iOS app development, so that became the new plan.
Slightly longer story short, between iOS tutorials, Claude, and ChatGPT, I managed to get something together in a few days. The old iPhone was stuck on an older version of iOS, which had to be factored in. The image below shows the very simple interface of the phone application, which shows markers for each location sent to the web application. After very little testing, the app was declared adequate, and off we went.
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| First test of the tracker application on a phone |
The final test of the swim tracker using the iOS application rather than the hardware tracker was on 15 August 2025 in Dover, England. We set off from the Dover Marina at 03:30 the morning, with the swim starting from Samphire Beach.
Unfortunately, about halfway through the channel, the swimmer had a very unexpected asthma attack and had to abandon the swim.
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| Swim start at Samphire Beach near Dover |
For the duration of the swim, the tracker worked pretty well. The phone application appears to have stopped outputting data on two occasions, which might be due to the application going into some sort of sleep. The two images below show what the tracker website page looked like on a phone and desktop computer during the swim.
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| Tracker web page on in a mobile browser |
The EE network SIM card worked well for the duration of the test. An Orange SIM was available as a backup.
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| Tracker web page on in a desktop browser |
Conclusion
Looking back at the first overview post, then most of the original requirements were achieved, although the tracker hardware was not used in the final test. It was interesting to work on the different parts of the project that ranged from hardware and embedded software to a web application.
It was a fun project to work on, even if the final swim did not turn out as expected.