How does altitude affect validity of a Polygon?

[dmtucker]

This seems to be required by the spec.

[dmtucker]

https://www.npmjs.com/package/point-in-polygon

inside(point, polygon)
Return whether point is contained in polygon.

point should be a 2-item array of coordinates.

polygon should be an array of 2-item arrays of coordinates.

[dmtucker]

Wikipedia Polygon

In geometry, a polygon /ˈpɒlɪɡɒn/ is traditionally a plane figure that is bounded by a finite chain of straight line segments closing in a loop to form a closed chain or circuit.

Wikipedia Plane

In mathematics, a plane is a flat, two-dimensional surface.

Should altitude be ignored?

[dmtucker]

I should note that geojsonhint validates this:

{
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "geometry": {
        "type": "Polygon",
        "coordinates": [
          [[0, 0, 0], [0, 0, 1], [0, 1, 1], [1, 1, 0], [1, 0, 0], [0, 0, 0]]
        ]
      },
      "properties": null
    }
  ]
}

which is clearly not planar.

[dmtucker]

Ignoring altitude guarantees a plane figure... and is also how geojson.io seems to behave when rendering.

Since our behavior depends on point-in-polygon, I say we table this issue for now.