Filter Aiding Measurements

The 3DM-GQ7 supports a variety of aiding measurements to improve the solution of the Navigation Filter. Aiding measurements are used to remove initialization and integration errors and maintain solution accuracy. Each aiding measurement (except external heading aiding) can be sourced internally from on-board sensors. Aiding measurements are enabled and disabled by the Aiding Measurement Enable (0x0D,0x50) command.

The availability and effectiveness of each aiding measurement will depend on the application and device configuration. To enable an aiding measurement, the Aiding Measurement Enable (0x0D,0x50) command must be sent once per aiding source. The table below captures the values that must be entered in the Aiding Source field to enable an aiding source.

 

Aiding Source	Value Entered in Aiding Source Field
GNSS position and velocity aiding	0
GNSS heading aiding (dual antenna)	1
Altimeter aiding	2
Speed sensor aiding	3
Magnetometer aiding	4
External heading aiding	5

A description of each aiding measurement is given below, along with any additional configuration commands required to use the aiding measurement.

 

GNSS Position and Velocity Aiding

This aiding measurement must be enabled for the Navigation Filter to use GNSS measurements in the navigation solution. This aiding measurement may be sourced from either the internal GNSS receivers (default) or an external receiver supplied by the user. Note that an internal and external GNSS source cannot be used simultaneously.

Internal source

Set the GNSS source to "internal" (default) using GNSS Aiding Source Control (0x0D,0x15). See Antenna(s) for antenna mounting and configuration instructions.

External source

Set the GNSS source to "external" using GNSS Aiding Source Control (0x0D,0x15), Use External GNSS Update (0x0D,0x16) to pass external GNSS solution data to the Navigation Filter. The maximum update rate is 2 Hz.

 

GNSS Heading Aiding (dual antenna)

Dual antenna heading aiding helps to maintain accurate absolute vehicle heading estimates, especially during quasi-stationary periods with minimal linear acceleration. It requires two GNSS antennas with a fixed baseline between them. See Antenna(s) for dual antenna mounting and configuration instructions. This aiding measurement can only be sourced internally.

 

Altimeter Aiding

Altimeter aiding can help stabilize altitude in challenging GNSS environments. It can only be sourced internally through the 3DM-GQ7's pressure altimeter.

 

Speed Sensor Aiding

Speed aiding can greatly improve navigation performance during GNSS outage scenarios.

Internal source

The 3DM-GQ7 supports direct digital inputs from an odometer. See Odometer for more information on odometer configuration.

External source

To provide speed measurements from an external speed sensor send the measurements to the Navigation Filter using (0x0D,0x60 Input speed measurement. The maximum update rate is 2 Hz.

 

Magnetometer Aiding

A measurement of the local magnetic field in conjunction with a location dependent model of Earth's magnetic field can be used for heading aiding. Special care must be taken when using this method. See Magnetometer Warning for details. This aiding measurement can only be sourced internally.

 

External Heading Aiding

External heading aiding helps to maintain accurate vehicle heading estimates, especially during quasi-stationary periods with minimal linear acceleration. An externally derived heading estimate can be supplied directly to the Navigation Filter using either External Heading Update (0x0D,0x17) or External Heading Update With Time (0x0D,0x1F), (preferred), if accurate timestamping for the external measurement is available.

External heading aiding can be applied either with or without enabling GNSS heading aiding.