Where Have You Been?

Here is an interesting picture:

Earlier this year, my partner and I holidayed in Dubrovnik, Croatia. This is a picture of that trip.

More exactly, its a picture of where I was during that holiday. I had set my phone to record its position every fifteen seconds or so. Then, when I was back home, I translated that data into the above image.

Every black pixel represents a point reported by my phone and we can pick out some pretty interesting features.

Firstly, the above is a zoom-in of a much larger image: This second image shows our visit to the island of Lokrum, and the kayak trip around the island.

For reference, here’s a picture of the same area, but in an actual map:

© OpenStreetMap contributors

Here’s some fun/interesting observations about these pictures:

Closer to Home

Since I started this project, over seven hundred days ago, I’ve accrued a lot of data. Most of that data, predictably, has been near my home. Obviously and unfortunately, I won’t be sharing a similar image to the above for my home town to protect myself and those I love, but here are some fascinating out-takes and the things I’ve learned.

As I said before, I wish I could share the whole image with you: it has a fascinating, eerie, vascular appearance and now lives in a picture frame on my wall. However, it’s just too much personal information to blast on the internet which brings me to my final point.

A Lot of Information in Not That Much Data

Seven hundred days worth of data is a lot, but also not that much. Zipped, all the data fits in 17MB. If you were to collate this information from every person in the UK, it would fill about a thousand external hard-drives of 1TB capacity5. That may sound like a lot, but it easily fits in a half-dozen shoeboxes of hard drives (or a single milk jug of SD cards)6.

And yet, you can read a lot in this data. Apart from where and when I holidayed, you could, with enough effort, work out where I ate, what activities I did and where I stayed. My home address lights up like a beacon, but so does the place I get coffee, my friends houses and my favourite walking routes. You can infer I haven’t worked out the shortest path to the station yet, and what sport I play.

This is three things: fascinating, private, and valuable. Its fascinating because one can learn so much about oneself just from where one goes; private because this is very intrinsic information that I want to be able to control access to; and valuable because it can be used to predict, monetise, and modify my behaviour.

It is well known that many organisations collect this data — indeed we give it to them in exchange for “free” services. However, it is a sobering reminder that every time you give that taxi, food delivery, or running app permission to see your location, you are giving them a lot more.


  1. I’m using the term GPS, though I know my phone uses a combination of GPS, GLONASS, Galileo and QZSS. Its just that GPS is a more universal abbreviation. ↩︎

  2. We were travelling during COVID — not because we thought it was a good idea, but because we had to in order to return to the country we live in. Global politics got… weird… for a while. ↩︎

  3. I should note that all these images are purposefully slightly grainy. This is both because it improves the style to have it rendered at low resolution (I think), and for privacy reasons. ↩︎

  4. It bugs me that “do archery” seems to be the correct English verb. I suppose it is technically “shooting”, but one can’t specify that one “shoots archery”. I think the best option was presented to me by an Italian lecturer who, upon noticing that I had my kit with me, exclaimed “Oh! You arch!” ↩︎

  5. Possibly even less due to the magic of compression. ↩︎

  6. https://what-if.xkcd.com/31/ ↩︎