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What I need is a function for Non Earth Coordinates in QGIS (both projects and layers). They should be mappable to any projected coordinate system (like SWEREF99TM).

Why: In the Mining industry we often use Non Earth systems for different reasons. Like Geophysics we want to define North in a convenient direction. Could be South East we don't care about the real world at this stage. The same if an ore body is going south-east we may define that direction as north.

In many softwares (Microstation or MapInfo) we use we can have on the fly conversion between lets say myCoordinateSystem1 (cartesian system) to EPSG3006 no problem. But I have not found a good function for this in QGIS.

I wonder if the Proj4 limits QGIS so you can't do this? Any solutions for this?

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  • EPSG3006 is found in qgis, and to add SWEREF99M usin like this "+proj=utm +zone=33 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs"
    – Fran Raga
    May 8, 2019 at 9:51
  • How is the Cartesian system defined in MapInfo/Microstation? Are there control points in both systems? There has to be some way to georeference the local system to a projected/geographic coordinate system.
    – mkennedy
    May 8, 2019 at 18:12
  • The Cartesian system is defined as x,y,z. And the origio of that cartesian system is defined in one point in a earth system like Sweref99TM or WGS84. @mkennedy The system will then be set at that point. What MS and MapInfo does then is to fix scale issues. It will not be exact and the problem grows with distance. But when we do work in nature we are never in big areas so that gives us a problem.
    – PeterW
    May 9, 2019 at 10:49
  • @Fran Raga, yes I know that Sweref99TM is defined that is not the problem, I need a non earth system that I can relate to Sweref99 or WGS84 or whatever. Meaning that I define my own system with my own north and so on. Then I relate that to whatever geografical system and the software does a rotation and translation of my own defined system.
    – PeterW
    May 9, 2019 at 10:54
  • @PeterW have you solved your problem? I getting stuck with the same issue...
    – CarolineC
    Apr 22, 2020 at 9:50

1 Answer 1

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I work with the same kind of things all the time and the way I do it is create a custom projection. Go to Settings > Custom Projections. It is easiest to enter a proj4 string and reference it to a wgs84 lat-lon (but you can do other projections too).

Example string:

+proj=omerc +lat_0=0 +lonc=0 +alpha=45 +gamma=0 +k=1 +x_0=20000 +y_0=55000 +ellps=WGS84 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs +type=crs

The important values are:

  • +lat_0 is the origin latitude

  • +lonc is the origin longitude

  • +alpha is the rotation from north

  • +k is the meters scale factor

  • +x_0 is the x coordinate you want in your "non-earth" system to be at the origin lat-lon specified above.

  • +y_0 is the y coordinate you want in your "non-earth" system to be at the origin lat-lon specified above.

I set my origin to somewhere near my project, or better yet at my survey control base station. I use offsets to make sure work never takes me to negative coordinates and I use very different x and y numbers so you can't easily get them confused (eg 20000/55000). As you said, over short distances a scale factor of 1 is fine.

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