What can happen when map projections is used for a purpose for which it is not designed?

Answer 1

A "projection" is used to convert the pattern of the spherical Earth to a flat sheet of paper. All projections imply some amount distortion; the only accurate map is a globe. We can generally reduce, or even minimize, the impact of the distortion by selecting proper type of projection.

Using a map with the wrong type of projection for the wrong area can lead you to make mistakes. For example, most of us have seen standard Mercator projection maps of the entire world. Look at one now. You see South America? You see Greenland? On a Mercator map, Greenland looks bigger. On the Earth, Greenland is MUCH smaller than South America!

Large scale (small area) maps can be quite accurate, but small scale (large area) maps are bound to cause some distortion. Here's another example; look at a map that shows both the USA and England. Which direction would you fly from San Francisco, California to London, England?

If you said "east", you wasted a LOT of fuel; the correct answer is "north-northeast". The shortest path from SFO to Heathrow goes north over Canada, almost to the pole, before "curving" south to Scotland and England. The straight line on the map isn't the same as the straight line on the globe!