[cs02rm0]

Amazing. I've been tracking a delivery (Seiki 4k monitor incidentally) which I believe is currently on this flight: http://www.flightradar24.com/ABX2040

It always looks as though the course they take is unnecessarily far north. I have to consciously remind myself that the map projection and the prevailing winds play a factor. This really does beautifully illustrate why they take the route they do.

[mxfh]

This is not far north because of winds, it's just the shortest line!

Great circle distance (Curves in Mercator, straight lines on globe) vs. Rhumb lines (Straight in Mercator, constant course angle against meridians)

http://demonstrations.wolfram.com/ComparingLoxodromesAndGrea...

[edit] added picture for explanation

http://i.imgur.com/wJS0ry1.png

Lines of same color have identical course

[cs02rm0]

Sort of, journeys in the other direction are pushed even further north (or, actually north of the straight line) though which I believe is because of the winds. - i.e. it's a factor, isn't it?

[mxfh]

Jet Streams are a factor but their position varies.

The appearance as a northbound curve is the effect of the straight Orthodrome/Great Circle line projected into Mercator.

http://en.wikipedia.org/wiki/Transatlantic_flight#Transatlan...

[edit] I think it's fair to assume the winds are relatively stable and more intense further north so eastbound (US > Europe) flights might deviate even further to the north.

http://en.wikipedia.org/wiki/North_Atlantic_Tracks#Route_Pla...

http://earth.nullschool.net/#current/wind/isobaric/10hPa/ove...

[kzrdude]

The map projection on google maps is only chosen to produce good maps at every point by themselves (square city blocks will still be square, wherever you zoom in). I assume they would have chosen a different design (a globe) if they designed it to be used as a world map service.

[jofer]

No, it's chosen because it preserves direction. They use a single Mercator projection centered at the equator.

It's a pragmatic choice, but it's certainly not chosen to produce good local maps. It produces bad local maps everywhere except the equator.

If they wanted to produce "good maps at every point by themselves", they'd use a different projection every time you recenter the map.

It's a terrible projection at every point not on the equator. However, it does preserve direction, so straight N-S or E-W streets will appear perfectly straight.

However, square city blocks _do not_ appear square. You just don't notice the distortion unless you're quite far north or south.