Cartographers were once the kings of the world, depicting all that was known of land and sea—and marking all that was not with the warning "Terra Incognita," or even "Here Be Dragons." Today, we are all mapmakers, thanks to powerful computer programs from Google and others that allow us to look at the planet in radical new ways. Putting the latest technology to the test as he travels—virtually and otherwise—from New York to San Francisco to Silicon Valley, Mike Di Paola goes where no man has gone before

Click the graphic above for a primer
on Google Earth and Google Maps.

The glare is unnaturally bright, the way it might appear to one who has risen late, perhaps with a hangover. Some of the people hanging around San Francisco's Union Square seem to be in that very state, sitting in the noon sunshine with a look of placid resignation. Others are in motion—in cars, on foot, astride bicycles, or aboard a cable car about to climb Powell Street.

The feeling of déjà vu is strong. I've been to Union Square once before, nearly twenty-five years ago, to hear Democratic vice presidential candidate Geraldine Ferraro speechify. But that's not what I'm recalling. What I'm thinking of is the opening scene of The Conversation, where Francis Ford Coppola pans his camera around the square and focuses, ironically, on an annoying mime in the crowd. My visit today is as silent, and even more remote.

Nowadays, one can experience Union Square, and just about every other point on the planet, without actually leaving the house. At this particular moment, I happen to be in New York City, 2,600 miles from the streets of San Francisco. But I can navigate them on Google Earth, a computer program that simulates the globe—and beyond. With supernatural ease, I descend toward Union Square from the sky like a god. Starting thirteen thousand miles above the surface, I swoop down through the atmosphere at a dizzying speed and come to an abrupt stop eight hundred feet above the 2.6-acre plaza.

From this vantage point I find that, contrary to Gertrude Stein's line about the city across the bay, there is a lot of there here: innumerable photographs; buildings rendered in three dimensions; icons indicating hotels, restaurants, and other places of interest. I enter Street View, a digital milieu of thousands of high-resolution images stitched together into a (mostly) seamless 360-degree ground-level panorama. The virtual environment is traversable by mouse-propelled carriage, which I click repeatedly.

The No. 5 cable car appears frozen on Powell, though it could well be chugging uphill, as it has a green light. I can see people aboard the car, but their faces have been digitally "scrubbed" by a face-blurring technology intended to protect privacy. I could proceed along Powell, tracing the path the Google cameras took up Nob Hill. It doesn't look all that steep in Street View—which is odd, since the cable car was invented to conquer these very hills. But there are more faithful simulacra of this location. The photosharing Web site Panoramio, which has been conveniently integrated into Google Earth, has a shot showing the precipitous climb, and Path Profiler allows me to precisely measure the grade (it rises 134 feet in three tenths of a mile). Returning to the skies, I count the palm trees (there are fifteen) en route to the stratosphere, where a Clouds function updated hourly by NASA shows clear weather over California but a spiraling storm center off the coast of Baja.