Purpose of the Software¶

Workflow¶

csvForWKT is a python script that creates a WKT-crs for solar system bodies. The physical content of the WKT-crs comes from the IAU Working Group on Cartographic Coordinates and Rotational Elements report.

The workflow to generate the WKTs is described as follows:

Positive longitudes¶

One body can be defined by one of the two following shapes:

a biaxial body
a triaxial body

At each shape, we can define three reference frames :

planetocentric frame with a sphere for interoperability purpose
planetocentric frame
planetographic frame

For a spherical shape, the planetocentric latitude and the planetographic latitude are identical. So a planetographic latitude is used.

Planetographic longitude is usually defined such that the sub-observer longitude increases with time as seen by a distant, fixed observer

Positive logitudes in one direction are defined with the following rule

start

if (historical reason or IAU_code >= 9000?) then (yes)
:East;
stop
else (no )
if (ocentric frame ?) then (yes)
:East;
stop
else (no)
if (rotation == "Direct" ?) then (yes)
:West;
stop
else (no)
:East;
stop
endif
endif
endif — Positive longitude rules¶

List of projections¶

The list of supported projections is defined as below :

Table of projections¶

Projections¶
Code	Projection name
10	Equirectangular, clon = 0
15	Equirectangular, clon = 180
20	Sinusoidal, clon = 0
25	Sinusoidal, clon = 180
30	North Polar
35	South Polar
40	Mollweide, clon = 0
45	Mollweide, clon = 180
50	Robinson, clon = 0
55	Robinson, clon = 180
60	Tranverse Mercator
65	Orthographic, clon = 0
70	Orthographic, clon = 180
75	Lambert Conic Conformal
80	Lambert Azimuthal Equal Area
85	Albers Equal Area

Detailed description for Equirectangular, clon = 0¶

Projection code: 10
Projection name: Equirectangular, clon = 0
Projection method: Equidistant Cylindrical
Latitude of 1st standard parallel: 0
Longitude of natural origin: 0
False easting: 0
False northing: 0

Detailed description for Equirectangular, clon = 180¶

Projection code: 15
Projection name: Equirectangular, clon = 180
Projection method: Equidistant Cylindrical
Latitude of 1st standard parallel: 0
Longitude of natural origin: 180
False easting: 0
False northing: 0

Detailed description for Sinusoidal, clon = 0¶

Projection code: 20
Projection name: Sinusoidal, clon = 0
Projection method: Sinusoidal
Longitude of natural origin: 0
False easting: 0
False northing: 0
None: None

Detailed description for Sinusoidal, clon = 180¶

Projection code: 25
Projection name: Sinusoidal, clon = 180
Projection method: Sinusoidal
Longitude of natural origin: 180
False easting: 0
False northing: 0
None: None

Detailed description for North Polar¶

Projection code: 30
Projection name: North Polar
Projection method: Polar Stereographic (variant A)
Latitude of natural origin: 90
Longitude of natural origin: 0
Scale factor at natural origin: 1
False easting: 0
False northing: 0

Detailed description for South Polar¶

Projection code: 35
Projection name: South Polar
Projection method: Polar Stereographic (variant A)
Latitude of natural origin: -90
Longitude of natural origin: 0
Scale factor at natural origin: 1
False easting: 0
False northing: 0

Detailed description for Mollweide, clon = 0¶

Projection code: 40
Projection name: Mollweide, clon = 0
Projection method: Mollweide
Longitude of natural origin: 0
False easting: 0
False northing: 0
None: None

Detailed description for Mollweide, clon = 180¶

Projection code: 45
Projection name: Mollweide, clon = 180
Projection method: Mollweide
Longitude of natural origin: 180
False easting: 0
False northing: 0
None: None

Detailed description for Robinson, clon = 0¶

Projection code: 50
Projection name: Robinson, clon = 0
Projection method: Robinson
Longitude of natural origin: 0
False easting: 0
False northing: 0
None: None

Detailed description for Robinson, clon = 180¶

Projection code: 55
Projection name: Robinson, clon = 180
Projection method: Robinson
Longitude of natural origin: 180
False easting: 0
False northing: 0
None: None

Detailed description for Tranverse Mercator¶

Projection code: 60
Projection name: Tranverse Mercator
Projection method: Transverse Mercator
Latitude of natural origin: 0
Longitude of natural origin: 0
Scale factor at natural origin: 1
False easting: 0
False northing: 0

Detailed description for Orthographic, clon = 0¶

Projection code: 65
Projection name: Orthographic, clon = 0
Projection method: Orthographic
Latitude of natural origin: 0
Longitude of natural origin: 0
False easting: 0
False northing: 0

Detailed description for Orthographic, clon = 180¶

Projection code: 70
Projection name: Orthographic, clon = 180
Projection method: Orthographic
Latitude of natural origin: 0
Longitude of natural origin: 180
False easting: 0
False northing: 0

Detailed description for Lambert Conic Conformal¶

Projection code: 75
Projection name: Lambert Conic Conformal
Projection method: Lambert Conic Conformal (2SP)
Latitude of false origin: 40
Longitude of false origin: 0
Latitude of 1st standard parallel: 20
Latitude of 2nd standard parallel: 60
Easting at false origin: 0
Northing at false origin: 0

Detailed description for Lambert Azimuthal Equal Area¶

Projection code: 80
Projection name: Lambert Azimuthal Equal Area
Projection method: Lambert Azimuthal Equal Area
Latitude of natural origin: 40
Longitude of natural origin: 0
False easting: 0
False northing: 0

Detailed description for Albers Equal Area¶

Projection code: 85
Projection name: Albers Equal Area
Projection method: Albers Equal Area
Latitude of false origin: 40
Longitude of false origin: 0
Latitude of 1st standard parallel: 20
Latitude of 2nd standard parallel: 60
Easting at false origin: 0
Northing at false origin: 0

How the IAU code is created¶

The IAU code is created according to this relation:

<naif_code> * 100 + <x_crs> + <code_projection>
where :
    x_crs = 0 for SPHERE Ocentric
            1 for ELLIPSE Ographic
            2 for ELLIPSE Ocentric
            3 for TRIAXIAL Ographic
            4 for TRIAXIAL Ocentric

    code_projection is one of the code in the projection table