Coordinate Systems for Display

Several display tools are available for use with the Aerospace Blockset™ product. Each tool has a specific coordinate system for rendering motion.

MATLAB Graphics Coordinates

See the Axes Appearance for more information about the MATLAB® Graphics coordinate axes.

MATLAB Graphics uses this default coordinate axis orientation:

  • The x-axis points out of the screen.

  • The y-axis points to the right.

  • The z-axis points up.

FlightGear Coordinates

FlightGear is an open-source, third-party flight simulator with an interface supported by the blockset.

The FlightGear coordinates form a special body-fixed system, rotated from the standard body coordinate system about the y-axis by -180 degrees:

  • The x-axis is positive toward the back of the vehicle.

  • The y-axis is positive toward the right of the vehicle.

  • The z-axis is positive upward, that is, wheels typically have the lowest z values.

AC3D Coordinates

AC3D is a low-cost, widely used, geometry editor available from https://www.inivis.com. Its body-fixed coordinates are formed by inverting the three standard body coordinate axes:

  • The x-axis is positive toward the back of the vehicle.

  • The y-axis is positive upward, that is, wheels typically have the lowest y values.

  • The z-axis is positive to the left of the vehicle.

Unreal Engine Coordinates

Unreal Engine® uses a left-handed world-fixed coordinate system with the z-axis positive upward. Positive rotations about the x-axis and y-axis are right-handed, whereas positive rotation about the z-axis is left-handed.

The Aerospace Blockset functionality sends Euler angles to Unreal Engine. These angles are applied in the order of rotations being yaw (z-axis), pitch (y), and roll (x-axis).

The coordinate system conversion between Simulink® to Unreal Engine involves conversion from a right-handed to a left-handed system, which, for the NED frame is done by flipping the sign of the z-axis.

Cesium for Unreal Coordinates

Cesium® uses the same world coordinate system as Unreal Engine. When the world origin is aligned with the center of the Earth at the ECEF location, then the y-axis is inverted from the ECEF coordinate system.

In Cesium, when the origin is at the center of the earth

  • The x-axis is in the plane of the equator, passing through the origin and extending from 180 degrees longitude (negative) to the prime meridian (positive).

  • The y-axis is also in the plane of the equator, passing through the origin and extending from 90 degrees East longitude (negative) to 90 degrees West longitude (positive). This is inverted from the ECEF y-axis.

  • The z-axis is in the line between the North and South Poles, with positive values increasing northward.

For more information on ECEF coordinate systems, see ECI and ECEF Coordinates.

See Also

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