Agilent Technologies Agilent E6474A - Manual (Page 76)

76 Agilent E6474A User’s Guide
4 Use Your System
display shows either 2D or 3D, with the GPS Status
displaying “Tracking.” Both speed and direction are also
displayed. If the Nav Mode shows 3D, the altitude readings in
the display are also valid.
Before starting a data collection test, allow three minutes for
the unit to acquire GPS position data. During a data collection
test, navigation data is also combined and collected.
Calibration of dead reckoning
The Dead Reckoning calibration system is virtually
self-calibrating and requires minimal user intervention. Once
the Agilent direct connect GPS/DR is properly connected and
the unit is powered on for the first time, it is not yet calibrated
and operates as a normal GPS receiver.
Once navigation begins using GPS signals, the receiver
automatically calibrates the sensors. During this calibration
process, the vehicle must be maneuvered in a specific manner
in order for the unit to calibrate, as follows:
1 Stop the vehicle for at least three seconds in order to
determine the gyro bias.
2 Drive in a straight line for a distance of approximately one
kilometer (0.62 mile).
3 Turn the vehicle, and proceed in another straight line for
approximately one kilometer (0.62 mile).
The period of time and distance traveled that are required for
the system to calibrate the Dead Reckoning sensors vary
depending on the GPS signal quality and receiver temperature
stability. The calibration continuously refines itself as you
drive.
NOTE
Toshiba JCDMA phones have special power-up procedures. Refer to
“Toshiba phone power-up issues" on page 104 for more information.