One photo, one pin. How close can you get?
Postcard is a daily photo geography game. Each day a photograph of a real place appears, which might be a famous landmark, a city street, a waterfall, a desert or a mountain range, and you drop a single pin on the world map where you think it was taken. When you lock in your guess, the real location is revealed with the distance between your pin and the spot, and you score up to 5,000 points. The closer you are, the more you get, and 2,500 points (a pin within roughly 1,000 km) wins the day. Everyone gets the same photo each day.
Say the photo shows an enormous column of orange-red rock rising straight out of flat green jungle, with terraced gardens and the remains of a stone staircase at its foot. The light is hard and tropical, and there are palms in the foreground. Nothing in the frame is written down. The vegetation says the tropics. The rock and the ruined gardens say an ancient royal site, and the lowland jungle rules out the mountains of Southeast Asia. A careful player thinks of South Asia and zooms in on Sri Lanka.
That is Sigiriya, the fifth-century rock fortress in Sri Lanka’s Central Province. A pin near Kandy, 75 km away, scores 4,755. A pin in Colombo, 151 km away, still scores 4,520. Someone who guesses southern India and pins Chennai is 572 km off and scores about 3,400, which is still a comfortable win. Mumbai is 1,500 km away and scores about 1,840, a loss. Bangkok, the obvious guess for anyone thinking of Thai temples, is 2,250 km away and scores about 1,100. Getting the right region is worth far more than getting the exact spot.
Your score depends only on the distance between your pin and the place in the photo, measured along the surface of the Earth (the great-circle distance). A pin within 1 km scores the full 5,000 points. After that the score falls away smoothly: about 4,970 at 10 km, 4,670 at 100 km, 3,580 at 500 km, 2,570 at 1,000 km, 1,320 at 2,000 km and 180 at 5,000 km. Distances are measured on the globe, not on the flat map, so they are correct across the Pacific and near the poles, where a flat map badly stretches things.
The curve is generous near the target and harsh far from it. Getting the right country usually matters far more than getting the right street, so it is worth spending most of your time working out the region before you fine-tune the pin.
The daily is won with 2,500 points or more. In practice that means placing the photo within about 1,000 km, roughly the distance from London to Berlin. Your result card shows the verdict, the distance, the score and how far short of 2,500 you were if you missed it.
Start with what cannot lie. Vegetation tells you climate: palms and dense green for the tropics, conifers for the north, scrub and bare rock for deserts. The sun’s height and the length of shadows say something about latitude. Water matters too. A turquoise lagoon inside a reef suggests the tropical Pacific or Indian Ocean, while a grey sea under cliffs suggests the North Atlantic.
Then look at what people made. Building materials and roof shapes vary by region in ways that are easy to learn: whitewashed walls and blue doors around the Mediterranean, carved wooden temples in East Asia, adobe in the Andes and the Sahel. Scripts on signs narrow things down at once, even when you cannot read them. Telling Cyrillic from Greek, or Devanagari from Thai, is often enough to win the day.
There are 133 places in the collection, spread across every inhabited continent. They range from world-famous monuments such as Angkor Wat, Petra, Chichén Itzá and the Acropolis to natural sites many people have never heard of, like Caño Cristales in Colombia, the Chocolate Hills of Bohol and the Champagne Pool in New Zealand. Every photo is a real photograph from Wikimedia Commons, used under its free licence (public domain, CC0, CC BY or CC BY-SA). The photographer and licence are credited on the photo itself, with a link to the original.
Each place is located using the coordinates of its Wikipedia article, and after you guess the result card tells you a little about it, with a link to read more. The photos are chosen so the place can be worked out from what is in the frame. There are no close-ups of a wall, no anonymous beaches and no photos with the name written on them.