Chapter 3 SPAN OperationOEM7 SPAN Installation and Operation User Manual v4 99l Course Over Groundl Inertial Azimuthl ALIGN Azimuth3.8.1 Course Over GroundThe course over ground azimuth is determined using the position delta between two positionsolutions computed by the OEM7 receiver. This is the simplest way to compute an azimuth and isdone using either the GNSS solution or the INS solution. This method does not work when thevehicle is stationary as any position difference is due to position error and the computed azi-muth is meaningless.Course over ground azimuth is of greatest advantage in aerial or marine environments wherethe actual direction of travel may not match the forward axis of the aircraft/boat due to winds orcurrents. This effect is known as the crab angle. Course over ground azimuth is a great way tocompute 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 21: Logswith Azimuth Data below.3.8.2 Inertial AzimuthThe inertial azimuth computed by the SPAN inertial navigation filter. It uses the sensors in theIMU to compute the azimuth of the IMU (this can be rotated to another reference if desired). Formore information, see the SETINSROTATION command in the OEM7 Commands and LogsReference Manual.This azimuth is the one provided in the majority of the INS logs available to a SPAN user. SeeTable 21: Logs with Azimuth Data below.3.8.3 ALIGN AzimuthOn 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 theinertial azimuth and is available at a much lower rate, but will have a stable mean. This azimuthis computed from the master antenna to the rover antenna based on how the antennas are ori-ented on the vehicle.There is a specific subset of logs that output this azimuth. See Table 21: Logs with Azimuth Databelow.Log LogFormat Azimuth SourceBESTVEL NovAtelCourse Over GroundFrom the best system solution which could be eitherGNSS or INSGPHDT NMEA ALIGNTable 21: Logs with Azimuth Data
