GroundVehicle Attitude Reference Frames

•MJ2000 Earth Equator

•Velocity-Local-Tangent (VLT)

•East-North-Up (ENU)

•Z-axis: Vector normal to the mean equatorial plane at Julian year 2000.0, pointing towards the Northern Hemisphere

•X-axis: Vector pointing from the center of the Earth to the mean vernal equinox at Julian year 2000.0

•Y-axis: Vector perpendicular to the x-axis and z-axis, forming a right-handed coordinate system

•Origin: Center of the Earth

•This is the principal coordinate system used for computations in FreeFlyer

•Commonly referred to as Mean of J2000, J2000, ECI, or GCI

•X-axis: Vector pointing in the direction of the body-fixed velocity of the GroundVehicle

•Y-axis: Vector perpendicular to the GroundVehicle's z-axis and x-axis, forming a right-handed coordinate system

•Z-axis: Vector pointing in the direction normal to the reference ellipsoid at the central body fixed position of the GroundVehicle

•Origin: Center of the GroundVehicle

•In the case that the VLT frame is not defined, it will fall back to the ENU frame.

•When using terrain the Z-axis is defined as the normal to the terrain at the location of the GroundVehicle on the terrain.

•X-axis (East): Vector pointing in the east direction of the Ground Vehicle's position vector

•Y-axis (North): Vector perpendicular to the GroundVehicle's z-axis and x-axis, forming a right-handed coordinate system

•Z-axis (Up): Vector pointing in the direction normal to the reference ellipsoid at the central body fixed position of the GroundVehicle

•Origin: Center of the GroundVehicle

•In the case that the ENU frame is not defined (at the Poles), the frame will fall back to x pointing along the prime-meridian, z pointing along the body-fixed z-axis, and y completing the triad.