Novatel OEM7 SPAN, Инструкция по установке и эксплуатации

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Chapter 3 SPAN Operation
OEM7 SPAN Installation and Operation User Manual v14 120
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Course Over Ground
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Inertial Azimuth
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ALIGN Azimuth
3.8.1 Course Over Ground
The course over ground azimuth is determined using the position delta between two position solutions computed
by the OEM7 receiver. This is the simplest way to compute an azimuth and is done using either the GNSS solu-
tion or the INS solution. This method does not work when the vehicle is stationary as any position difference is
due to position error and the computed azimuth is meaningless.
Course over ground azimuth is of greatest advantage in aerial or marine environments where the actual direction
of travel may not match the forward axis of the aircraft/boat due to winds or currents. This effect is known as the
crab angle. Course over ground azimuth is a great way to compute the offset if another means of computing the
vehicle azimuth is available.
Course over ground azimuths are available in several different velocity logs. See Table 29: Logs with Azimuth
Data below.
3.8.2 Inertial Azimuth
The inertial azimuth computed by the SPAN inertial navigation filter. It uses the sensors in the IMU to compute
the azimuth of the IMU (this can be rotated to another reference if desired). For more information, see the
SETINSROTATION command in the OEM7 Commands and Logs Reference Manual .
This azimuth is the one provided in the majority of the INS logs available to a SPAN user. See Table 29: Logs
with Azimuth Data below.
3.8.3 ALIGN Azimuth
On SPAN systems with dual antennas, an azimuth is available from the dual antenna baseline. This is the same
azimuth that is used as an update to the SPAN solution. It is noisier than the inertial azimuth and is available at a
much lower rate, but will have a stable mean. This azimuth is computed from the master antenna to the rover
antenna based on how the antennas are oriented on the vehicle.
There is a specific subset of logs that output this azimuth. See Table 29: Logs with Azimuth Data below.
Log
Log
Format
Azimuth Source
BESTGNSSVEL NovAtel
Course Over Ground
From the best GNSS only solution
BESTVEL NovAtel
Course Over Ground
From the best system solution which could be either GNSS or
INS
GPHDT NMEA ALIGN
GPVTG NMEA
Course Over Ground
From the best system solution which could be either GNSS or
INS
Table 29: Logs with Azimuth Data