It turns out to have been a career starter for Mr Ruser, 22, who has morphed his fascination with mapping, data and satellite imagery into a job in Canberra with the International Cyber Policy Centre at the Australian Strategic Policy Institute.

Surprisingly, though, Mr Ruser is not himself especially careful with his own data. He doesn't have an exercise app, but because he has an Android phone, his movements are recorded on Google Maps Timeline. This means he can tell you where he was at any given time on any given day and his life is conveniently recorded down to the last detail. But isn't he concerned about the privacy and security implications?

Not really, he says. He's confident that Google understands the implications of the data in a way that Strava evidently didn't, and while he says the data is possibly accessible if someone really works for it, he doubts that is happening.

"I don't have particularly great privacy," he says, suggesting it's a generational thing - young people know and accept that privacy no longer exists.

"I kind of keep my data out of the hands of people that I don't want to have it, but [I'm] not going out of my way to stop Google getting my data.

"I have hygiene with my data but I don't go out of my way to not leave any digital trace."

Mr Ruser is fast becoming an expert on satellite and other open-source data, which he is using to research human rights abuses, cultural disruption and genocide, such as the treatment of the Rohingyas in Myanmar and the Uyghurs in China.

Asked what he's working on, he says: "Mostly I like to use the unbiased and unrestricted nature of satellites to reveal a lot of the human rights abuses that are happening, where governments and other actors look to restrict information and cover up the truth."

The beauty of satellites is that it is "mostly impossible to hide", with clouds the only barrier to what is happening on the ground.

Some parts of the world, though, are only visible through a fuzzy lens. High-resolution satellite images have a pixel size of 30 centimetres squared, and you need about three pixels to see clearly, allowing objects about the size of a car to be seen effectively, he says.

US law, though, prohibits the distribution of satellite imagery of Israel at resolution greater than one metre squared - which Mr Ruser says leaves Israel as one of the least visible countries on Earth.

The super-high-resolution data is generally "tasked" by an agency or organisation which pays for satellites to image certain regions. Which means more data is available for areas that agencies are interested in. But not always.

"If you look at Afghanistan or Iraq on Google Earth, somewhere someone has told Google Earth not to get recent high-res imagery," he says.

"But there are ways to get around it."

Parts of Afghanistan have nine-year-old images on Google Earth, and outside the main centres and towards the Pakistan border the picture becomes suddenly fuzzy. Iraq is similar.

Very occasionally, as in the battle of Mosul, the US buys exclusive rights, with the result that during the battle no one could see what was happening on the ground.

Mr Ruser said he has had to pay just once so far, spending $100 to buy the rights to images of a village in Myanmar that Google Earth had decided not to buy.

He also uses satellite data from non-visible wavelengths, such as infrared, useful for building pictures of activities such as vegetation clearing and the movement of water.

Schooled at an academically selective school in Manly, the son of parents who worked IT and fire investigation, Mr Ruser moved to Canberra in 2016 to study international security. But he says the satellite work was self-learned, "sort of just me seeing what was possible".

It grew, he says, out of his natural tendency to see things spatially, to place things on a mental map, and from his interest in finding out what was happening in the world beyond available news.

He has a distinctly understated style, evident in his tweet which first alerted people to the trove of information available via Strava - and the risks for operational security.

"It looks very pretty, but not amazing for Op-Sec. US bases are clearly identifiable and mappable," he tweeted in January 2018, adding helpfully in brackets: "Turning off data sharing is an option."

"This particular track looks like it logs a regular jogging route. I shouldn't be able to establish any pattern of life info from this far away."

His revelation, which sparked a flurry of posts of military and other activity, also prompted a review from Strava which said it was working with military and government officials to address potentially sensitive data.

He says he found the reaction surprising.

"I didn't expect that many people would be that interested, I sort of expected that it would sort of languish in the open source community as a little neat tool and not gain a heap of interest," he says.

"But it seems people were interested."