=?UTF-8?B?SsO2cmcgJ1lhZGdhcicgQmxlaW1hbm4=?= <yazdegird@gmx.de> wrote:
> > Does this introduce any distortion into the way the asteroid map is applied to
> > the object? (I guess I need to read up on latitude and longitude!) I'm thinking
> > there might be, at the North and South 'poles.' Just guessing, out of ignorance.
>
> The maps to use here are so-called "simple cylindrical projections" -
> this means that on the map, longitudes and latitudes form a rectangular
> grid, each parallel crosses each meridian at a 90 degree angle, unlike
> in most other map projections which are designed to avoid as much
> distortion as possible. Also, with the simple cylindrical projection,
> all distances between latitudes are equal, unlike Mercator's projection
> which stretches to infinity at the poles. When "re-projected" to a
> sphere, the 2D distortion of the simple cylindrical projection disappears!

The official cartographical term is "equidistant cylindrical projection" (aka
"plate carree projection").

Not to be confused with what POV-Ray calls a "cylindrical" projection - which
actually is an "equal-area cylindrical projection" (any subtype will do for
POV-Ray, e.g. Gall-Peters projection, Behrmann projection or Lambert
cylindrical equal-area projection, as they just differ in the way they are
"squeezed" to a certain aspect ratio, which is irrelevant for use in POV-Ray).

The "equidistant cylindrical projection" matches what POV-Ray calls "spherical
projection".

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