User Manual
© 2017 Inertial Sense, LLC
9
11/30/2017
3
Coordinate Frames
In this manual,
coordinate frame systems
are simply referred to as
frames
. This section is to assist the developer in
choosing and implementing the appropriate coordinate frames for their respective application. It should be noted
that the following
frames
are in relation to the uINS itself.
3.1
Sensor Frame
IMU, magnetometer, and INS velocity data are in the Sensor Coordinate Frame, or Sensor Frame, and are
identified by the X, Y, and Z axes labeled on the hardware. The z-axis is positive down into the image.
3.2
INS Output Frame
The INS output data (DID_INS_1, DID_INS_2, DID_INS_3) is in the
INS Output Frame
. Translation from
Sensor
Frame
to
INS Output Frame
is defined as:
1.
Sensor Frame
→
Intermediate Output Frame
by rotation of DID_FLASH_CONFIG.insRotation euler angles
(in order of heading, pitch, roll angle) In radians.
2.
Intermediate Output Frame
→
INS Output Frame
: Offset by DID_FLASH_CONFIG.insOffset in meters.
If DID_FLASH_CONFIG.insRotation and DID_FLASH_CONFIG.insOffset are zero, the
Sensor Frame
and the
INS
Output Frame
are the same.
3.3
North-East-Down (NED) Frame
Position estimates can be output in the North-East-Down (NED) coordinate frame defined as follows:
•
Right-handed, Cartesian, non-inertial, geodetic frame with origin located at the surface of Earth (WGS84
ellipsoid).
•
Positive X-axis points towards North, tangent to WGS84 ellipsoid.
•
Positive Y-axis points towards East, tangent to WGS84 ellipsoid.
•
Positive Z-axis points down into the ground completing the right-handed system.
3.4
Earth-Centered Earth-Fixed (ECEF) Frame
The Earth-Centered Earth-Fixed (ECEF) frame is defined as follows:
•
Right-handed, Cartesian, non-inertial frame with origin located at the center of Earth.
•
Fixed to and rotates with Earth.
•
Positive X-axis aligns with the WGS84 X-axis, which aligns with the International Earth Rotation and
Reference Systems Service (IERS) Prime Meridian.
X
+Roll
Z
+Yaw
Y
+Pitch
X
+Roll
Z
+Yaw
Y
+Pitch
