IntelliTrack Module
Operations Guide
AvL Technologies
| Proprietary – Content is Subject to Change without Notice
pg. 16
The Topocentric origin (the terminals location) is then similarly transformed to an ECI position.
The magnitude of the direction vector derived from look angle can then be determined such
that the sum of the Topocentric origin and the converted vector has a magnitude matching what
is required for Geostationary satellites described in the ECI frame (42,164 km). The final sum of
the two vectors represents the target position in the ECI frame as noted in Figure 10.
Scaled Direction
Vector
TopoCentric
Origin
Look Angle
Direction Vector
Target Position
Required Radius: 42,146 km
Figure 10 - Earth-Centered Inertial Vector Solution
In order to simplify the mathematical model, the target position is then converted from ECI
coordinates into Geodetic coordinates. The Geodetic coordinate frame describes the position of
an object in terms of Latitude (
φ
), Longitude (
λ
), and Altitude (
h
) (height from the surface of the
earth). This coordinate frame was selected for managing the mathematical model as it allows
the Altitude (
h
) to be fixed, leaving only two free variables to be characterized. A representative
Geodetic path for an inclined geostationary satellite is described in Figure 11.
