γ = tan
−1
µ
2q
y
q
z
+ 2q
w
q
x
q
w
q
w
− q
x
q
x
− q
y
q
y
+ q
z
q
z
¶
, (C.8)
where q =< q
w
, q
x
, q
y
, q
z
>. In this context, the Yaw angle with respect to the ENU (East-
North-Up) frame represents the heading from East to North. To get the heading of the
sensor from the North in a clockwise direction, we need to compute 90◦-yaw. Alterna-
tively, the user can calculate the rotation in NED (North-East-Down) coordinates and then
extract the Roll-Pitch-Yaw angles with respect to NED, where yaw would be directly the
heading in common sense. The function EcefPoseToEnuEul(), in the Fixposition GNSS
Transformation Lib, receives the pose of the sensor in ECEF coordinates and returns the
orientation of the robot in Yaw-Pitch-Roll angles using the equations described above.
VRTK output coordinate system:
The receiver output is always in the coordinate reference system (geodetic datum) used
by the correction data service. In RTK mode, the receiver does relative positioning with
respect to the base coordinates provided by the correction data service. The system in
which those base coordinates are is entirely up to the correction data service provider.
The receiver does not need or use this information at all. This is true for all ECEF (XYZ)
output. For lat/long/height output, the WGS84 parameters are used to transform ECEF
XYZ to lat/lon/height. In non-RTK mode, the output position is WGS84.
Vision-RTK 2 | Fixposition Positioning Sensor 80
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