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I can't seem to figure out a way to define a custom PROJ4 projection that can mirror geometries (e.g. inverse x to -x and y to -y and vice versa). Other than that, I don't need any transformations or reprojections. I am simple trying to show arbitrary (x,y) coordinate pairs from an SVG in a GIS system (OpenLayers and/or QGIS).

I think the main problem is that in SVG, the origin (0,0) is situated at the Top-Left. However, I have no clue how to account for that difference..

I have seen that PROJ4 allows transformations (+towgs84) but I figured that's not what I should use. I know from visualizing my geometry in QGIS and OpenLayers that a 'mirror functionality' is all I need.

I am open for other solutions than projections, but I figured that defining a new projection would be easiest. I do need an automated way though.

TL;DR:
I would like to mirror-transform (projection or something else) X,Y-coordinates for using in QGIS or OpenLayers without use of external libraries or plugins.

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  • Does PROJ.4 allow a scale factor of -1? I think it doesn't and has a check of must be >0.
    – mkennedy
    Commented Dec 13, 2017 at 19:32
  • Thanks, so that means I can't use any projection?
    – Matthie456
    Commented Dec 14, 2017 at 7:32

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