3 ms·

That's still not an accurate map. 3D maps don't have projection issues, they can have near perfect representation of the world.

by jbob2000 8y ago

jacobolus 8y ago
The eyes see a 2-dimensional picture. Computer displays produce a 2-dimensional picture. There is no such thing as a “3D map” on a standard computer display. Only an orthographic (or maybe perspective) projection which animates in response to user input. In general an orthographic projection is a poor choice. The thing going for it is that it is easy to understand by analogy to a physical globe, and human spatial understanding can partially compensate for the distortion by imagining a sphere. But there are also disadvantages, for example on an orthographic projection north is not always vertical, latitude and longitude lines are neither perpendicular nor straight, shapes and areas can be very dramatically distorted near the edge of the map, there are dramatic distance errors between far away points or points not in the center of view, it is impossible to view more than half of the planet’s surface in one view, etc. There are many other choices of map projections, and for any particular purpose, some other projection is usually better.
- mikeash 8y ago
  Regardless of what the eye sees, the brain perceives three dimensions. This projection happens to be the one that the brain can automatically unpack into an accurate 3D representation. Technically, things near the edges are squished and distorted, but that gets undone in the wetware.
  - jacobolus 8y ago
    You really can’t get an accurate sense of angles/shapes, areas, distances, or directions with an orthographic projection except by moving the view around. Even when you do, it is very difficult to accurately compare attributes of regions which are far away on the globe, and easy to mislead yourself. (This is a problem with physical globes as well.) For many types of mapping use cases, orthographic projections are substantially worse than other possible choices. Sometimes physical spheres (or virtual representations of spheres as dynamic orthographic or perspective projections) are nice. That’s why I spent a whole bunch of time building myself a spherical chalkboard, for example. But they aren’t the best choice for any purpose. Personally I don’t think they make a very good choice for a general-purpose world map. They are better as a supplement to flat maps.
  - jacobolus 8y ago
    Let me give you a concrete example. Here is what North America looks like on this new map: https://i.imgur.com/lCI8DjY.jpg https://i.imgur.com/lCI8DjY.jpg This is not a good projection to use if you want to see all of North America. There is dramatically more distortion than necessary, and shapes near the edges get very squished (the west coast of the US is okay), but it is not at all obvious to a naïve viewer what kind of distortions are involved, and past experience looking at soccer balls or whatever isn’t going to fix it. (Note: a Mercator projection is also not a good choice for this. On a Mercator projection sizes are dramatically bloated as you go north.)
    - mikeash 8y ago
      I'm not convinced it isn't still the best option. The naive viewer may not properly perceive the distortions, but I bet they'll get closer than with anything else, for general purposes. What projection would you say would be good for that view?
      - jacobolus 8y ago
        For North America per se you could e.g. pick the conformal projection with roughly constant scale around the boundary of the continent (one world atlas does this), or you could pick a projection which minimized distance errors (there are several possible ways of quantifying those, which will yield different maps), or you could pick among several equal-area projections (especially useful if you want to make a choropleth map), or for something dynamic you could use an azimuthal equidistant projection or some conic projection (e.g. Lambert conformal conic, Albers equal-area conic), or .... https://pubs.er.usgs.gov/publication/pp1395 https://pubs.er.usgs.gov/publication/pp1395 There are many choices. An orthographic projection is generally one of the worst except insofar as it gives the impression of a physical sphere when you zoom all the way out.
- Robotbeat 8y ago
  You can, of course, use VR to get a stereoscopic 3D display as well, like what humans see in the real world. Except for depth of field (which some prototype VR systems can still accomplish), that's as 3D as real life. And Google Maps/Earth VR can indeed do that.
  - quadrangle 8y ago
    what about focus?
    - Robotbeat 8y ago
      Some VR companies are working on that.
- jofer 8y ago
  I'm amazed this has been downvoted so much... As the OP stated, "globe" view (a.k.a. orothographic or perspective, depending) is not fundamentally better than other projections. It has tradeoffs. You should always choose the projection that matches your use case. A map is a visualization tool. The goal is not to reflect reality as accurately as possible. The goal is to communicate data and spatial relationships. Projections are part of that. There is not a "best" projection. Orthographic with some animations is a nice visual tool for some purposes and terrible for others. How could pointing this out be controversial? A bar graph is not a perfect representation of a group of numbers, but it's a very useful visualization. A map is no different than any other visualization.

That's still not an accurate map. 3D maps don't have projection issues, they can have near perfect representation of the world.

jacobolus 8y ago

The eyes see a 2-dimensional picture. Computer displays produce a 2-dimensional picture. There is no such thing as a “3D map” on a standard computer display. Only an orthographic (or maybe perspective) projection which animates in response to user input. In general an orthographic projection is a poor choice. The thing going for it is that it is easy to understand by analogy to a physical globe, and human spatial understanding can partially compensate for the distortion by imagining a sphere. But there are also disadvantages, for example on an orthographic projection north is not always vertical, latitude and longitude lines are neither perpendicular nor straight, shapes and areas can be very dramatically distorted near the edge of the map, there are dramatic distance errors between far away points or points not in the center of view, it is impossible to view more than half of the planet’s surface in one view, etc. There are many other choices of map projections, and for any particular purpose, some other projection is usually better.

mikeash 8y ago
Regardless of what the eye sees, the brain perceives three dimensions. This projection happens to be the one that the brain can automatically unpack into an accurate 3D representation. Technically, things near the edges are squished and distorted, but that gets undone in the wetware.
- jacobolus 8y ago
  You really can’t get an accurate sense of angles/shapes, areas, distances, or directions with an orthographic projection except by moving the view around. Even when you do, it is very difficult to accurately compare attributes of regions which are far away on the globe, and easy to mislead yourself. (This is a problem with physical globes as well.) For many types of mapping use cases, orthographic projections are substantially worse than other possible choices. Sometimes physical spheres (or virtual representations of spheres as dynamic orthographic or perspective projections) are nice. That’s why I spent a whole bunch of time building myself a spherical chalkboard, for example. But they aren’t the best choice for any purpose. Personally I don’t think they make a very good choice for a general-purpose world map. They are better as a supplement to flat maps.
- jacobolus 8y ago
  Let me give you a concrete example. Here is what North America looks like on this new map: https://i.imgur.com/lCI8DjY.jpg https://i.imgur.com/lCI8DjY.jpg This is not a good projection to use if you want to see all of North America. There is dramatically more distortion than necessary, and shapes near the edges get very squished (the west coast of the US is okay), but it is not at all obvious to a naïve viewer what kind of distortions are involved, and past experience looking at soccer balls or whatever isn’t going to fix it. (Note: a Mercator projection is also not a good choice for this. On a Mercator projection sizes are dramatically bloated as you go north.)
  - mikeash 8y ago
    I'm not convinced it isn't still the best option. The naive viewer may not properly perceive the distortions, but I bet they'll get closer than with anything else, for general purposes. What projection would you say would be good for that view?
    - jacobolus 8y ago
      For North America per se you could e.g. pick the conformal projection with roughly constant scale around the boundary of the continent (one world atlas does this), or you could pick a projection which minimized distance errors (there are several possible ways of quantifying those, which will yield different maps), or you could pick among several equal-area projections (especially useful if you want to make a choropleth map), or for something dynamic you could use an azimuthal equidistant projection or some conic projection (e.g. Lambert conformal conic, Albers equal-area conic), or .... https://pubs.er.usgs.gov/publication/pp1395 https://pubs.er.usgs.gov/publication/pp1395 There are many choices. An orthographic projection is generally one of the worst except insofar as it gives the impression of a physical sphere when you zoom all the way out.
Robotbeat 8y ago
You can, of course, use VR to get a stereoscopic 3D display as well, like what humans see in the real world. Except for depth of field (which some prototype VR systems can still accomplish), that's as 3D as real life. And Google Maps/Earth VR can indeed do that.
- quadrangle 8y ago
  what about focus?
  - Robotbeat 8y ago
    Some VR companies are working on that.
jofer 8y ago
I'm amazed this has been downvoted so much... As the OP stated, "globe" view (a.k.a. orothographic or perspective, depending) is not fundamentally better than other projections. It has tradeoffs. You should always choose the projection that matches your use case. A map is a visualization tool. The goal is not to reflect reality as accurately as possible. The goal is to communicate data and spatial relationships. Projections are part of that. There is not a "best" projection. Orthographic with some animations is a nice visual tool for some purposes and terrible for others. How could pointing this out be controversial? A bar graph is not a perfect representation of a group of numbers, but it's a very useful visualization. A map is no different than any other visualization.