I'm strolling through the port of Buenos Aires, the Argentinian capital. At the side of the road, six teens are sitting on a low wall, their legs dangling over the edge. One of them is waving. Loading cranes are visible in the background. A few meters down the road, two women are walking towards me, chatting excitedly. Where are they headed? I'll never know; the moment is frozen in time and I'm trapped, unable to escape. But within this one moment I am free to move: I turn into a street lined with palm trees. Here is where, shielded by high walls and fences, the rich reside in their villas, keeping the world at bay. Small huts dot their frontage at regular intervals, security guards patrol the sidewalks. It's a different world to the vibrant energy of the port – but one of many I will explore this afternoon. Step by step, from the comfort of my sofa, on Google Street View.

Surveying the world was once the preserve of scientists and explorers, and subsequently of the authorities and international organizations. Today, Google Street View has become the planet's cartographer. The service was launched in 2007 and now, according to its own data, its routes extend almost 20 million kilometers, covering famous sights such as the Grand Canyon in Arizona, the Pyramids of Giza in Egypt and even a footpath to Mount Everest in Nepal. Not to mention millions of kilometers of normal residential streets, major thoroughfares in glamorous cities, and narrow lanes in remote villages.

Some people may have spotted Google Street View cars in their neighborhood. They have a box on the roof, and each side has a camera that takes photos at short intervals. The vehicles have to maintain a slow speed. After that the process is fully automated, and the pictures are pieced together by computers. As a result, weird, funny or even frightening scenes can sometimes find their way onto the Web: a two-car collision, a man slipping on a banana skin, couples embracing –maybe while their unsuspecting spouses are waiting at home. There are countless collections of unusual Street View moments on the Internet.

But not all the recording is performed by cars. Street View also shows areas inaccessible to vehicles. To photograph the Grand Canyon, for example, a Google employee ventured the descent with a camera attached to his back. And in the Faroe Islands, cameras have been strapped onto grazing sheep. Even parts of Mars are featured: the exploration rovers Spirit and Opportunity sent back the film material.

Before launching into space, however, I search out my grandparents' house. And I can't help laughing: walking right outside it, carrying a shopping bag, is my Grandpa. At least I think it's him. In the window of the house I can see the horrendous plastic floral arrangement they had on display there a few years back. I had long forgotten that. And, in the picture, the house still hasn't had its fresh coat of paint. I think of the street scene in Buenos Aires, of the new buildings in Cambridge Bay. Their pictures too may be out of date. For all its appeal, Street View only offers a snapshot of life, and this snapshot may be several years old. After all, it can't photograph 20 million kilometers of road every few days.

But looking at my grandparents' house, I feel slightly disconcerted. On the one hand, it is fascinating and wonderful that Grandma, Grandpa and their house are embedded in this navigable world on the Internet, and therefore part of the huge universe that can be explored on Street View. On the other hand, it's frightening: my grandparents have no idea that their house is in plain sight – to anyone and everyone. Shots of residential buildings can, of course, be pixelated. Houses in Austria and Germany often are, more often than in other countries. Data privacy seems to be important in central Europe – but the protection comes at a price: you need to take the initiative and ask to be anonymized. Do nothing and your house will be visible on the Internet in all its glory. Do other providers offer a better service? Last year Apple Look Around was launched as an alternative to Google Street View. Despite coming from a gigantic company like Apple, it only shows a handful of American cities at present. EveryScape appears more advanced and prioritizes users sharing their own photos. While this is a smart approach, you can't typically roam and explore the streets.

So back to Street View. Notwithstanding all its controversies, the huge pictorial atlas not only benefits individuals who want to see places they plan to visit. It has itself become a new form of virtual tourism. Video tours are now available using the website. You can take trips to an array of sights in Italy and listen to commentaries. Artists are developing projects using the map service, and shops and restaurants are expanding their marketing by offering virtual walk-throughs. Street View is also being used in academic research – into areas like artificial intelligence. Its pictures help train computers to recognize individual people and buildings.

There's one item still on my bucket list. I want to blast off from the launchpad, and surge into the sky, right up to the International Space Station. Years ago, an astronaut equipped with suitable cameras photographed everything here. And it's almost exactly how I imagined it. Cables snaking around, electrical equipment everywhere. More like a vast construction site than a space station. Nevertheless, it makes me feel emotional. This isn't a simulation. These are real pictures of the ISS on Street View, and you can see everything. I climb into the cupola and look down at the Earth – the blue orb I share with 7.5 billion others. A snapshot, true. But truly beautiful as well.

Christian Heinrich is a freelance journalist who has worked for Die Zeit, Geo and Süddeutsche Zeitung.