Unit and Coordinate Conventions
- R D
- 1 Overview
- 2 Units
- 3 Coordinates
- 3.1 World space
- 3.2 World space relative altitude
- 3.3 Local space
- 3.4 Rotation
Overview
These are the conventions used by Autonomy.
Units
All units are in SI.
Angles are in radians.
Coordinates
World space
AKA global or absolute.
WGS 84: https://en.wikipedia.org/wiki/World_Geodetic_System
Axis | Origin |
|---|---|
Latitude [decimal degrees] | Equator, north is positive |
Longitude [decimal degrees] | IERS reference meridian (IRM) (prime meridian), east is positive |
Altitude [metres] | Mean sea level, away from centre of Earth is positive |
World space relative altitude
AKA global relative altitude.
WGS 84: https://en.wikipedia.org/wiki/World_Geodetic_System
Axis | Origin |
|---|---|
Latitude [decimal degrees] | Equator, north is positive |
Longitude [decimal degrees] | IERS reference meridian (IRM) (prime meridian), east is positive |
Relative altitude [metres] | Home position, away from centre of Earth is positive |
Local space
North east down (NED): https://en.wikipedia.org/wiki/Local_tangent_plane_coordinates
Axis (Euclidean) | Origin |
|---|---|
North [metres] | Home position, north is positive |
East [metres] | Home position, east is positive |
Down [metres] | Home position, towards centre of Earth is positive |
Rotation
The coordinate axes follow the right hand rule. When the axis is pointing towards you and axes are fixed, the angle increases in the counterclockwise direction.
The origin of the axes (i.e. 0 rotation) is specified in code as a comment. For example: The origin is the drone, so the camera gimbal rotates relative to the drone’s axes.
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