Agilent Technologies Agilent E6474A manual Calibration of dead reckoning, Use Your System

4Use Your System

NOTE

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:

1Stop the vehicle for at least three seconds in order to determine the gyro bias.

2Drive in a straight line for a distance of approximately one kilometer (0.62 mile).

3Turn 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.

Toshiba JCDMA phones have special power-up procedures. Refer to “Toshiba phone power-up issues" on page 104 for more information.

76 Agilent E6474A User’s Guide