Ptolemy's map and the importance of accuracy...
The 15th C. European explorers like Vasco de Gama and Magellean had it tough - not only did they have crappy boats, but they had no idea where they were going.
We have to give Ptolemy some credit - he's the first cartographer that had a pretty successful round globe painted on a 2-dimensional surface. It was SO good, we were still using the map 1,400 years later! But, he was fatally wrong with his map data. This leads Magellan and others to think that the spice islands we're a week's sail from the New World. Ouch - was he wrong about the size of the Pacific. The consequences of an inaccurate map were fatal.
I would argue that it's even more important for modern maps to be accurate - and the potential for accidents is very much still real if we go on the wrong map data. This is why we support Open Street Maps and their great work of creating extremely accurate maps of the whole world, using a crowd sourcing model in the likeness of Wikipedia.
With our increasing dependence on GPS and digital tools for navigation, maps must be correct. You can help the Open Street Map community, both with your time and your money, in creating the most accurate maps available. Click this link here to get more information on how you can get involved.