3 ms·

> The extra distance around Africa looks comparatively small on the Mercator projection. Compared to what? I.e. what projection or approach would you choose in

• dr-detroit 3y ago
  [dead]
• reliablereason 3y ago
  A projection that is better at showing the comparative difference in length between going through the Suez canal vs going around. The mercator makes Africa look comparatively small on the y-axis which is a problem if you are trying to visualise the size of Africa and the time it takes to go around the continent. If i visually compare the distance on the mercator and an equal area projection is looks to make the trip about 20% shorter on mercator (compared to the apparent visual distance going through Suez). Non of the projections will be 100% accurate but the mercator is less accurate for this specific case.
  • labcomputer 3y ago
    > The mercator makes Africa look comparatively small on the y-axis which is a problem if you are trying to visualise the size of Africa and the time it takes to go around the continent. LOL. The Suez canal is at ~30°N, while Cape Town is ~35°S. If anything the Mercator projection is exaggerating the visual distance of going around.
    • trgn 3y ago
      Hating on Mercator is just pavlovian concern trolling at this point (it's the first thing people learn in their GIS classes, whatever). People are so obsessed with conservation of area, it's cringey, Freud would have something to say about that. Maps should always neatly establish a frame of reference. Unless you need to actually take out a ruler and measure a thingie of of it, projections don't matter all that much. The mercator map is an excellent world map: land masses nicely proportioned, straight reference lines that don't clutter, north is up thank god, no weird bulges, just rectangular, you know, like a page in a book or a website. It's just a really good world map. The haters are wrong 90% of the time.
• isk517 3y ago
  Considering that the discussion is about shipping in the southern hemisphere then maybe choose one of the many different map projections that better represent that part of the world.
  • agos 3y ago
    such as?
• Y_Y 3y ago
  Many of you will be well aware that you can't have a distance-preserving "map", that is a projection from the globe to a segment to of the plane where the length of an arbitrary path is preserved. Hence you can't measure real-world distances using string and a paper map. That said you can preserve distance in special cases, for example any two chosen points. For example you can go to https://www.jasondavies.com/maps/two-point-equidistant/ https://www.jasondavies.com/maps/two-point-equidistant/ and put your points at the Suez Canal and the Cape of Good Hope. While that still won't let you measure wiggly ship routes along the coast, it does a better job than Mercator. Failing that you can use Gall-Peters which does a better job of conveying the vastness of Africa, since it's area preserving.
  • rightbyte 3y ago
    > Hence you can't measure real-world distances using string and a paper map. You very much can. The scale of longitude and latitude is just not the same so you need to do Pythagoras (usually by approximation rules). There are usually lines to allow for that.
    • Y_Y 3y ago
      If you only use rigid string and sail in strange curves that map to straight lines in 2d then that's true. Or maybe by "do Pythagoras" you meant to calculate the metric tensor for your projection and integrate that along your shipping route?
  • bevenhall 3y ago
    Is measuring distances in Google Earth misleading? Why bother with ancient flat maps?
    • deleted 3y ago
      [deleted]
    • kube-system 3y ago
      The measuring tool is accurate. The way it appears on your screen is always misleading in some way, because your screen is flat.
• logicchains 3y ago
  Ideal would be an embedded gif (or even interactive widget) of a 3D globe rotating, with the lines drawn on it, but obviously that's a lot more work.