DESIGNATE CARTOGRAPHIC

Syntax

Fixed

   DESIGNATE @int(1001:1099)
      CENTER @body
      REFERENCE CARTOGRAPHIC
      (2:3){ LATITUDE  @number
           | LONGITUDE @number
           | @options
           | RADIUS    @number }
      (0:3){ FROM  @calendar
           | TO    @calendar
           | EPOCH @calendar }

Moving

   DESIGNATE @int(1001:1099)
      CENTER @body
      REFERENCE CARTOGRAPHIC
      (2:3){ LATITUDE  (1:2)@number
           | LONGITUDE (1:2)@number
           | @options
           | RADIUS    (1:2)@number }
      EPOCH @calendar
      (0:2){ FROM @calendar
           | TO   @calendar }

Description

When creating a designated object in this system, you must specify the latitude and longitude of the object. The radius is optional, and defaults to the largest semi-major axis of the tri-axial ellipsoid used to model the body.

Definition

In cartographic coordinates, the z-axis points toward the north pole of the reference body. The x-axis is defined by the intersection of the equator and prime meridian of the body. The origin is at the center of the body.

Let P be a point in space, and let V be the position vector from the origin of the cartographic frame to P.

The cartographic latitude of P is the angle between the equator and V. North latitudes are positive, south latitudes are negative.

The cartographic longitude of P is the angle between the x-axis and the projection of V onto the x-y plane. With the exception of the Earth and Moon, the cartographic longitude of the sub-Earth point increases with time. (Thus, longitude is negative from x toward y for bodies with direct rotation, but positive from x toward y for bodies with retrograde rotation.) For the earth, the cartographic longitude is 90 degrees on the Y-axis. For the moon, the cartographic longitude is -90 degrees on the Y-axis.

The cartographic radius of P is the distance from the center of the reference body to P (the magnitude of V).

Examples

   ;
   ;  Define a name for the designated object (volcano Pele on Io).
   ;
   DEFINE PELE 1001;
 
   ;
   ;  Provide the location of Pele.
   ;
   DESIGNATE PELE
        CENTER IO
        REFERENCE CARTOGRAPHIC
        LATITUDE   -10 DEGREES
        LONGITUDE -100 DEGREES ;
 
   ;
   ;  Assume that the window CLEAR contains intervals when Io
   ;  is clear of Jupiter (not occulted, eclipsed, or in transit).
   ;  Subject to this constraint, find intervals when Pele is
   ;  visible from Earth.
   ;
   FIND VISIBLE TRANSIT OF PELE ACROSS IO FROM EARTH
        WITHIN IO_CLEAR;

Notes

If the radius is not specified, the default value may place the designated object above the surface of the reference body. To place an object on the surface of a reference body, use planetographic coordinates.