I'm building software and want to use good terminology for variables, tables, etc.

Most of my work involves blueprint drawings on which I render shapes (pins, polygons, etc). The same set of pins can be represented on different blueprints which has different "projections". The main blueprint is my "base projection".

  • A section blueprint of a beam will be rotated along x or y so it has a completely different coordinate system.

  • Another section blueprint can represent the same 2d plane as the base blueprint but with an offset origin and a different scale. I guess that the offset could be called datum, but I call it transform as is usual in computer graphics terminology.

For now I'm calling my different coordinate systems "Projections", but they are not projections in GIS terms, i.e. transformations from spherical to planar.

I'll soon implement support for working with maps, which will probably be WGS84 (Google maps). The term projection will for sure be used in that implementation.

Question: Should I call my 2D projections anything else than projections? Is there another term for this?

  • I guess (coordinate) reference system could be a more universally suitable term to use here? (dangerously) short and (very) simple: datum refers to the localisation on spheroids/ellipsoids, projection defines the derivation of planar representations of such a body ('s surface) and transformation the transfer [sic] of coordinates between different datums/projections. note: google maps uses the (infamous) spherical mercator projection, based on the WGS84 datum (e.g. for localisation), but projected from an auxilliary sphere (mainly for general performance reasons)
    – geozelot
    Jan 19 '18 at 16:46
  • The term "coordinate system" is already taken in my system. It's kind of a higher abstraction. My coordinate systems: "image" (pixels on blueprint image), "screen" (pixels on the screen), "blueprint" (mm on printed blueprint), "realworld" (mm in real world via blueprint scale), "device" (mm on device screen via device dpi). I'm aware that "projection" has a far more advanced meaning, hence my initial question.
    – Michael
    Jan 19 '18 at 16:58
  • well...*transformations* seems to be close enough, also following the mathematical principle if I´m not mistaken...EDIT: nevermind, it´s taken, too, right? just build some other software...,)
    – geozelot
    Jan 19 '18 at 17:02
  • Transformation would be great if it weren't already taken as well. In the SVG world a "transform" is defined via set of parameters; scaleX, scaleY, translateX, translateY, rotate, skewX, skewY (or a matrix).
    – Michael
    Jan 19 '18 at 17:04
  • @Michael are your coordinates geographic coordinates - i.e. do they represent Earth locations? Or are they abstract coordinates that do not take the shape of the Earth in consideration? Jan 19 '18 at 17:15

It seems like this question does not quite belong in the GIS site. But the question was answered in the comments, so I guess it was kind of right to put it here anyway.

As many pointed out, projection is not the right term. After understanding a bit more I totally agree.

ISO 19111 was the key. Much to learn from that paper for a newbie. It turns out that Datum is the term I need. Datum describes exactly what I want and it's also used both for geodetic and engineering (and also vertical) systems as per the standard.

Definition for Datum: A datum defines the position of the origin, the scale, and the orientation of the axes of a coordinate system.

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