Like let’s say that we start on the cape of goodwill for example and follow the coast.
Represent each 1km with 1mm for example on our map (map size isn’t a problem just for the sake of the argument). Getting the directions of drawing off a compass exactly. And just walk around all the coasts of the world.
What type of map do we end up with in this hypothetical?
In: 5
Let’s ignore coasts and think about some extreme examples:
* You start at the North Pole, move south 1km, move east 1km, and move north 1km. On paper, you’ve made a U shape, but under ideal conditions, you’ve put yourself back at the North Pole after moving in a sort-of-triangle.
* Using this same south-east-north plan, you start near the South Pole. There is one particular area where your eastward movement completes a full circle, and you are again back at your starting point, having retraced the same path north that you took going south. [This video](https://www.youtube.com/watch?v=OOzzncDp2oE) goes into cases where your eastward movement is closer to the SP and results in multiple circles.
* There is another area about half a kilometer north where your eastward movement only completes a semicircle, and you end up over 2km away, technically on the other half of the world.
* There is yet another area further south where you also return to your starting point, but your eastward movement also crosses over your south/north path. However, this might not count since you are crossing the SP—any movement away from the SP is technically north, and any movement towards is technically south.
* Even at the equator, your south-east-north path doesn’t quite result in you being 1km away from your starting point, but you are much closer to your planned U-shape than at any other latitude.
Part of the problem is that you can never actually walk in a straight line on the surface of a globe. Your path curves into the globe by some amount. With Earth as large as it is, this curvature is almost impossible to feel.
Another part of the problem is that every east/west path that isn’t along the equator curves to the left or right. You’d probably notice this in the polar examples given above.
For these small scale (very zoomed out charts) we use the Mercator projection in the maritime (actually for all paper charts, also larger scales)
The Mercator projections is basically the globe projected from the center onto a cylinder. The cylinder can then be rolled out to a flat sheet. This is stretching the drawing the more we are getting away from the equator, the classic “Greenland is as big as Africa”. But very interesting, the angles are true and makes it easy to put out courses.
We usually measure the length scale on the N/S edge of the charts, as the one end might have a significant different scale than the other when coming to precision plotting.
If you decided to make a chart with the same scale all the way, you end up making a very cubby looking chart where you can’t measure true angles or plot courses and positions easy.
When charts was hand drawn there was for a long time significant errors as it was a lot of triangulation calculation, but as the instruments and calculations got better, the maps also got better
Are maps inaccurate? Or are people using the wrong maps?
Mercator projection is the classic case. It is designed for navigation. If you use a protractor to measure an angle on the map, then followed that compass course, you would end up where you want to go (allowing for weather, terrain etc.)
It does distort the land shapes, but it is designed for accurate angles, not accurate representation of size.
Just as a screwdriver isn’t used for nails, or a hammer for screws (except in my city) it’s about picking the right tool for the job
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