From self-driving cars to smart bins, global satellite positioning (GPS) is fundamentally changing the world around us, but as more of Earth becomes accessible from our keyboards, there are a number of groups who want to swat prying eyes away.

Key points: Taiwanese missile sites were recently revealed by Google 3D mapping tools

Taiwanese missile sites were recently revealed by Google 3D mapping tools Online map providers follow local legislation that requires sensitive sites to be censored

Online map providers follow local legislation that requires sensitive sites to be censored Experts say sometimes the errors on maps are made on purpose

A cursory Google search will reveal plenty of online articles that list the hidden places — be it pixellation in France, disparate image resolution levels on the US-Mexico border, or dark spots that shroud Britain's home of nuclear missiles.

Searches by the ABC over southern Tibet using Google Maps's satellite mode for example, show unexplained grey boxes over certain areas — with one box greying out the entire Tibetan village of Guwacun.

Be it an error or done with serious intent, Amy Griffin, a senior lecturer in geospatial science at RMIT University's School of Science, says we shouldn't blame Google straight away.

"Google itself probably doesn't care about what sites you can see, it's relationships with other entities that drives what's taken down," Dr Griffin told the ABC.

"These requests are made usually by governments of various sorts because it has some kind of facility that they don't necessarily want publicly known — and they haven't made steps to disguise it in the landscape.

"With the number of satellites around, it's reasonably hard to hide things compared to how things used to be."

Governments no longer hold the keys to maps

Prior to GPS, illustration and aerial photography provided the bulk of cartographic information. ( Flickr: State Library of Victoria )

To begin to understand what prompts people to hide things on digital maps, it pays to take a step back to understand how cartography happens today.

In a pre-digital era, map surveyors would have been out on foot taking measurements and recording where things were in particular locations, which were then relayed to a map draughtsperson — usually part of a state topographical service.

Then, when flight became more common, topographical services began the practice of photogrammetry, where stereo images — image pairs that are slightly offset from each other — were compared using a stereoscope which then informed the creation of a topographic map.

Today, this process is largely automated as tech giants such as Bing, Google and Apple, use algorithms that grab satellite data and ground measurements from a variety of datasets to keep maps updated — meaning that they can usurp state topographical organisations.

Dr Griffin explained that in 2016, South Korea offered its state map data to Google on the proviso that it didn't expose sensitive military sites in high resolution, but the company refused.

That hasn't stopped Google from mapping the country in street view and satellite forms.

"Google's map service in South Korea is much poorer than it is in many other places because it doesn't have the same quality of data driving it," she said.

While countries still reserve the right to withhold map data, the number of state and private companies that sell satellite images makes hiding the globe incredibly difficult.

At the same time, this also means that state or non-state actors can beat private companies to the exclusive rights of a satellite image, meaning they can partially censor the image before others can license it.

Professor Anthony Stefanidis, director of the Criminal Investigations and Network Analysis Centre at George Mason University, said that this gives tech companies the "ability to impact geopolitics at scales unheard of".

"Even if Google opts to pixelate a particular area, there are numerous alternative sites and sources that provide that information," he said.

When resolution becomes a strategic tool

Tel Aviv, left, is shown in significant lower resolution compared to Melbourne, right. ( Google Maps / ABC News )

Today, map censorship is more likely to be appear as blurred areas with deliberate low resolution of pixellation over areas rather than black redacted marks on an official document.

The entire country of Israel appears at a low resolution as it has been illegal since 1998 for US companies to distribute high-resolution satellite images of the country.

But Israel has the heft of Washington largely behind it, whereas more marginalised American allies such as Taiwan — whose geopolitical power is often dominated by mainland China — aren't always as privileged.

Recently, Google 3D mapping tools inadvertently revealed a Taiwanese military installation housing American Patriot missiles — missiles that have previously angered China.

In 3D-mode, Google Maps shows close detail of a secret military complex in Taipei. ( Google Maps )

In response, the South China Morning Post reported that Taiwanese defence officials have officially asked Google to blur the locations, and Defence Minister Yen De-fa attempted to reassure citizens by saying that the "site of a military base does not equally mean its fixed position during wartime".

At maximum zoom, Google Maps shows loaded Taiwanese Patriot missiles. ( Google Maps )

At present, Google users can zoom right in to the trucks that carry the missiles.

The Defence Minister's comments echo previous attempts to confuse map users by simply leaving older images in circulation.

America's Tonopah Test Range — a subsection of a desert military installation in Nevada colloquially referred to as Area 51 — was found to have gone without an update from Google Earth in eight years.

"Because these tech giants yield often unchecked power, many people tend to vilify them," Professor Stefanidis said.

"[But] if one wants to get a true measure of censorship one should consider the fact that [Turkish President Recep Tayyip] Erdogan banned access to Twitter for Turkish citizens, while China has more-or-less banned access to Facebook for nearly a decade," he said.

But maps aren't always as they seem

While online maps today have made sizeable improvements in accuracy compared to their paper forebears, the two forms still can't be taken as articles of faith.

"A big misconception about maps is that what's on Google is 100 per cent accurate … it's not," Dr Griffin said.

"The way that mapping services build maps these days can lead to a variety of different errors creeping in," she said.

And sometimes these errors are on purpose.

The Hong Kong-Shenzen border presents users with sizeable misalignment. ( Google Maps )

In China, services such as Bing, Google and Apple have to use an encryption algorithm — an electronic mathematical tool that obscures topographical data that has purposefully offset where things actually are.

What results are street grids appearing in rivers, while border points don't actually match up.

When asked by the ABC about whether or not Google heeds to external requests to purposefully block parts of its maps, a Google spokesperson said: "We are aware of an issue with some Maps tiles and are investigating."

While it is "harder to completely go off the grid and still function in the modern world", as Dr Griffin explained, she warned that questions of censorship might play second fiddle to the implications of this era of technological surveillance.

"One of the things that a lot of people don't think about consciously is the degree to which we give our location to somebody else," she said.

"There are more and more companies and governments that have data about us, and this needs to be a bigger part of our public debate."