I'm using now for a couple of years Augmented Reality to visualize 3D-Models, but I never thought to much about the correct projection, when I create my 3D-Models. But for the current project I'm working on I noticed some gaps between 3D-Models which should actually be together.

Currently I'm using a self programmed QGis-Plugin to convert 2D-LineStrings into 3D-Pipes. The first step is to convert the 2D-LineStrings into a metrical coordinate system, in my case a UTM coordinate system. After that I do my calculation for the vertices, faces and normals to get a 3D-Pipe. Then I save every single 3D-Pipe to a .obj/.mtl file.

As an AR-SDK I'm using Wikitude, but I noticed the same behaviour as described above with Metaio (which is not available any more).

I take my 3D-Model and place them with a WGS84 coordinate into the AR-Scene.

The anchor point is normaly the first point from the 2D-LineString.

Roughly it's working but not exactly. Probably I get better results if I'm using the pseudo mercator coordinate system, but I'm not sure.

I'm also not 100% sure what kind of procetion is used in an AR-Scene. I guess that it is a metrical system (OpenGL) which is maybe transformed to a global system like WGS84, which would explain why I could place 3D-Models with a WGS84 coordinate.

To recap everything:

  • In which metrical coordinate system should I transform my 2D-LineStrings to do my calculations to get the most accurate results in an AR-Scene.
  • What kind of projection is used in an AR-Scene.
  • Small bump, I still hope to find someone to shed some light! :) – Sceada Jun 11 '18 at 16:29

In case you're using the Unity Wikitude SDK, Unity uses a left-handed coordinate system, but they haven't specified any particular metrical coordinate system, while the WGS84 is a right-handed coordinate system. You might want to watch out for that, when you convert your 3D data.

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