Hi Bill,

I've played with Robert Orso's QWE File converter and a number of planets
maps (Thank you, Robert, for your piece of software). I have noted a strange
behaviour with retrograde rotation planets (Venus, Uranus and Pluto): if the
original cylindrical maps respects IAU conventions on cartographic
coordinate system (*) the resulting planet images in Guide are rotated
(Venus) or mirrored (Uranus and Pluto).
Have I misunderstood a key step or there is a bug in Guide? (Please, note as
Venus and Uranus/Pluto behave differently).
For testing purpose, you can use the attached "cylindrical maps" for planets
in prograde and retrograde rotation.

Cheers,

Tiziano Magni, Italy

------------------------

(*) From the "Report of the IAU/IAG working group on cartographic coordinate
and rotational elements of the planets and satellites: 2000":

(...)
The north pole is that pole of rotation that lies on the north side of the
invariable plane of the solar system.
(...)
In mathematical and geodetic terminology, the terms "latitude" and
"longitude" refer to a right-hand spherical coordinate system in which
latitude is defined as the angle between a vector passing through the origin
of the spherical coordinate system and the equator, and longitude is the
angle between the vector and the plane of the prime meridian measured in an
eastern direction. This coordinate system, together with Cartesian
coordinates, is used in most planetary computations, and is sometimes called
the planetocentric coordinate system. The origin is the center of mass.
Because of astronomical tradition, planetographic coordinates (those used on
maps) may or may not be identical with traditional spherical coordinates.
Planetographic coordinates are defined by guiding principles contained in a
resolution passed at the fourteenth General Assembly of the IAU in 1970.
These guiding principles state that:
(!!!)
1. The rotational pole of a planet or satellite which lies on the north side
of the invariable plane will be called north, and northern latitudes will be
designated as positive.
(!!!)
2. The planetographic longitude of the central meridian, as observed from a
direction fixed with respect to an inertial system, will increase with time.
The range of longitudes shall extend from 0° to 360°.
Thus, west longitudes (i.e., longitudes measured positively to the west)
will be used when the rotation is prograde and east longitudes (i.e.,
longitudes measured positively to the east) when the rotation is retrograde.
The origin is the center of mass. Also because of tradition, the Earth, Sun,
and Moon do not conform with this definition. Their rotations are prograde
and longitudes run both east and west 180°, or east 360°.


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