Position Types for an Area Target
The Centroid page for area targets enables you to define the "center" point of an area target. The centroid is used as, among other things, a terminal point for access lines drawn to the area target during animation.
Select a Position Type, and enter the appropriate values. The options available will depend on the Position Type you select.
Position Type
STK provides five ways of positioning the location of an area target's centroid:
Geodetic Position
| Option | Description |
|---|---|
| Latitude | Measured in degrees from -90.0 degrees to +90.0 degrees. The geodetic latitude of a point is the angle between the normal to the reference ellipsoid and the equatorial plane. |
| Longitude | Measured in degrees from -360.0 degrees to +360.0 degrees. The longitude of a point is the angle between the projection of the position vector in the equatorial plane and the prime meridian. It is measured as increasing in a counterclockwise sense when viewed from the north pole. |
| Altitude | Specified as distance above or below the reference ellipsoid. Altitude is measured along the normal to the surface of the ellipsoid.
The reference ellipsoid refers to our mathematical geometric model of the Central Body. For Area Target centroids located on Earth, STK uses WGS84 (World Geodetic System 1984). |
Spherical Position
| Option | Description |
|---|---|
| Latitude | Measured in degrees from -90.0 degrees to +90.0 degrees. The spherical latitude is the angle of the position vector above the equatorial plane. |
| Longitude | Measured in degrees from -360.0 degrees to +360.0 degrees. The longitude of a point is the angle between the projection of the position vector in the equatorial plane and the prime meridian. It is measured as increasing in a counterclockwise sense when viewed from the north pole. |
| Radius | Distance of the object from the center of the Central Body. |
Cartesian Position (Fixed)
| Option | Description |
|---|---|
| X | The X component of the object's position vector, where the X-axis crosses 0 degrees/0 degrees latitude/longitude. |
| Y | The Y component of the object's position vector. |
| Z | The Z component of the object's position vector, where the Z-axis points to the North pole. |
Cylindrical Position
| Option | Description |
|---|---|
| Radius | Polar radius, where  |
| Longitude | Measured in degrees from -360.0 degrees to +360.0 degrees. The longitude of a point is the angle between the projection of the position vector in the equatorial plane and the prime meridian. It is measured as increasing in a counterclockwise sense when viewed from the north pole. |
| Z | The Z component of the object's position vector. |
Geocentric Position
| Option | Description |
|---|---|
| Latitude | Measured in degrees from -90.0 degrees to +90.0 degrees. The geocentric latitude of a point is the spherical latitude of the sub-point on the surface of the Central Body.
The sub-point refers to the intersection of the projection with the ellipsoid. The point may be on terrain or on a vehicle. The point then can be projected down to the surface and the intersection is the sub-point. |
| Longitude | Measured in degrees from -360.0 degrees to +360.0 degrees. The longitude of a point is the angle between the projection of the position vector in the equatorial plane and the prime meridian. It is measured as increasing in a counterclockwise sense when viewed from the north pole. |
| Altitude | Specified above or below the reference ellipsoid. Altitude is measured along the normal to the surface of the ellipsoid.
The reference ellipsoid refers to our mathematical geometric model of the Central Body. For Area Target centroids located on Earth, STK uses WGS84 (World Geodetic System 1984). |