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Assuming that a set of positions are all inside a 5km square area:
How do I find/define a projection to reproject the positions, so that the relative positions between the now reprojected positions are exact?

This would mean that for any pair of objects inside that 5km square area; If I do distance = obj1.EastingNorthing - obj2.EastingNorthing I will get a distance vector whose value has less than 1cm of error, in relation to the true distance.

Is there a single projection that I can use globally?
Does it have to be a different projection for each square? How do I build it?

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  • What are you trying to render your 3D scene with? Is it a web map or something?
    – Tangnar
    Commented Jul 24, 2015 at 12:30
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    It depends on what you mean by "projection". If you mean "coordinate reference" (projection plus parameters), then of course the answer is "No." If you're willing to create locally appropriate parameters, then multiple projections are available (depending on the definition of "anywhere" (the need for polar mapping).
    – Vince
    Commented Jul 24, 2015 at 13:42
  • I think knowing some more about what you are trying to accomplish would help. Can you give an idea of what your final goal is, in a little more detail?
    – Tangnar
    Commented Jul 24, 2015 at 15:07
  • EPSG:3857 will NOT give you true distances. Only on the equator the web mercator distances in x and y are correct.
    – AndreJ
    Commented Jul 24, 2015 at 15:29
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    If you build a local transverse mercator CRS where lat_0 and lon_0 is in the center of your scene, you will have true distances within 5 kilometers.
    – AndreJ
    Commented Jul 27, 2015 at 15:54

1 Answer 1

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If you build a local transverse mercator CRS where lon_0 and lat_0 is in the center of your scene, you will have true distances within 5 kilometers:

+proj=tmerc +lon_0=7 +lat_0=51 +k=1 +x_0=0 +y_0=0 +datum=WGS84 +units=m +towgs84=0,0,0,0,0,0,0 +no_defs

It should work in the ARCGIS world just the same.

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