4 ms·

I've kind of felt, that modern GIS software is very much still tied up to 2D map sheets and projections and their distortions. Why not entirely move to 3D globe

I've kind of felt, that modern GIS software is very much still tied up to 2D map sheets and projections and their distortions. Why not entirely move to 3D globe based representations and processing?

mc32 7y ago
So... those bulbous TV screens from back when they don’t use flat CRTs might project maps better at certain scales...
bryanrasmussen 7y ago
My general feeling on the matter is that 2d representations are an abstraction of the 3d reality, as such, they are probably useful in the same way that abstractions are generally useful for understanding highly complicated things.
zokier 7y ago
Unless you are talking about VR, the visuals are going to be viewed on a 2D screen. And to get the 3D globe on 2D screen you need some sort of projection.
- billfruit 7y ago
  But that screen projection will not have effect on calculations performed on the globe. Otherwise also I fail to see why this is a valid argument. The viewpoint usually is manipulatable to view the globe from any desired point of view.
  - jacobolus 7y ago
    What you are proposing in practice is to always use some kind of perspective or orthographic projection, but make it easy for viewers to change the projection parameters (by rotating/zoomming). But an orthographic projection is strictly inferior to other projections for essentially every purpose by every criterion except “draw a picture of what the earth might look like if viewed from space”. * * * As for "calculations": these should not be done in terms of latitude/longitude if it can be avoided. Personally I think we should switch to using stereographic projection as an internal data format. Here’s my draft writeup https://observablehq.com/d/5e75dd8e56fe255f https://observablehq.com/d/5e75dd8e56fe255f
    - billfruit 7y ago
      I am not suggesting using an orthographic projection. What I was suggesting was using a 3d earth model, which will be rendered on the screen using a perspective projection. Does not the earth viewed from space indicate true shapes, distances, and areas?
      - lmz 7y ago
        > Does not the earth viewed from space indicate true shapes, distances, and areas? Surely some areas will be out of sight, or squished to the sides of the globe.
      - jacobolus 7y ago
        > Does not the earth viewed from space indicate true shapes, distances, and areas? Of course not. A perspective projection distorts "true" shapes, sizes, and distances more than any other common choice of map projection, and in addition leaves more than half of the globe out of sight.
        billfruit 7y ago
        But in an interactive display that is not of concern. It allows us to rotate and move vantage point to see different parts of the globe, as much as a real globe would allow someone to peruse.
  - zokier 7y ago
    I'm not a GIS expert, but I would have assumed that any calculations would be performed on the geoid model (or whatever) instead of on the projected map? Is that really not the case?
stdbrouw 7y ago
Because it's very cumbersome to work in 3D, for very little benefit. Projection error can be as little as a couple of meters over hundreds of kilometers if you choose a proper projection (and creating your own conic projection is easy, too.) In exchange for that error you can calculate distances using Pythagoras' theorem instead of Vincenty's formula or whatever. If you have to calculate whether X is in <geometry> for millions of points, which is typical for a GIS analysis, you can do that in 2D on your own laptop or in 3D on a supercomputer.
deleted 7y ago
[deleted]

I've kind of felt, that modern GIS software is very much still tied up to 2D map sheets and projections and their distortions. Why not entirely move to 3D globe based representations and processing?

mc32 7y ago

So... those bulbous TV screens from back when they don’t use flat CRTs might project maps better at certain scales...

bryanrasmussen 7y ago

My general feeling on the matter is that 2d representations are an abstraction of the 3d reality, as such, they are probably useful in the same way that abstractions are generally useful for understanding highly complicated things.

zokier 7y ago

Unless you are talking about VR, the visuals are going to be viewed on a 2D screen. And to get the 3D globe on 2D screen you need some sort of projection.

billfruit 7y ago
But that screen projection will not have effect on calculations performed on the globe. Otherwise also I fail to see why this is a valid argument. The viewpoint usually is manipulatable to view the globe from any desired point of view.
- jacobolus 7y ago
  What you are proposing in practice is to always use some kind of perspective or orthographic projection, but make it easy for viewers to change the projection parameters (by rotating/zoomming). But an orthographic projection is strictly inferior to other projections for essentially every purpose by every criterion except “draw a picture of what the earth might look like if viewed from space”. * * * As for "calculations": these should not be done in terms of latitude/longitude if it can be avoided. Personally I think we should switch to using stereographic projection as an internal data format. Here’s my draft writeup https://observablehq.com/d/5e75dd8e56fe255f https://observablehq.com/d/5e75dd8e56fe255f
  - billfruit 7y ago
    I am not suggesting using an orthographic projection. What I was suggesting was using a 3d earth model, which will be rendered on the screen using a perspective projection. Does not the earth viewed from space indicate true shapes, distances, and areas?
    - lmz 7y ago
      > Does not the earth viewed from space indicate true shapes, distances, and areas? Surely some areas will be out of sight, or squished to the sides of the globe.
    - jacobolus 7y ago
      > Does not the earth viewed from space indicate true shapes, distances, and areas? Of course not. A perspective projection distorts "true" shapes, sizes, and distances more than any other common choice of map projection, and in addition leaves more than half of the globe out of sight.
      - billfruit 7y ago
        But in an interactive display that is not of concern. It allows us to rotate and move vantage point to see different parts of the globe, as much as a real globe would allow someone to peruse.
- zokier 7y ago
  I'm not a GIS expert, but I would have assumed that any calculations would be performed on the geoid model (or whatever) instead of on the projected map? Is that really not the case?

stdbrouw 7y ago

Because it's very cumbersome to work in 3D, for very little benefit. Projection error can be as little as a couple of meters over hundreds of kilometers if you choose a proper projection (and creating your own conic projection is easy, too.) In exchange for that error you can calculate distances using Pythagoras' theorem instead of Vincenty's formula or whatever. If you have to calculate whether X is in <geometry> for millions of points, which is typical for a GIS analysis, you can do that in 2D on your own laptop or in 3D on a supercomputer.

deleted 7y ago

[deleted]