Navigation Messages

Estimated State

This message presents the estimated state of the vehicle.

EstimatedState is a complete description of the system in terms of parameters such as position, orientation and velocities at a particular moment in time.

The system position is given by a North-East-Down (NED) local tangent plane displacement (x, y, z) relative to an absolute WGS-84 coordinate (latitude, longitude, height above ellipsoid).

The symbols for position and attitude as well as linear and angular velocities were chosen according to SNAME’s notation (1950). The body-fixed reference frame and Euler angles are depicted next:

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Euler angles

• Abbreviation: EstimatedState
• Identification Number: 350
• Fixed Payload Size: 0

Name	Abbreviation	Unit	Type	Description	Range
Latitude (WGS-84)	lat	rad	fp64_t	WGS-84 Latitude.	Same as field type
Longitude (WGS-84)	lon	rad	fp64_t	WGS-84 Longitude.	Same as field type
Height (WGS-84)	height	m	fp32_t	Height above the WGS-84 ellipsoid.	Same as field type
Offset north	x	m	fp32_t	The North offset of the North/East/Down field with respect to LLH.	Same as field type
Offset east	y	m	fp32_t	The East offset of the North/East/Down field with respect to LLH.	Same as field type
Offset down	z	m	fp32_t	The Down offset of the North/East/Down field with respect to LLH.	Same as field type
Rotation over x axis	phi	rad	fp32_t	The phi Euler angle from the vehicle’s attitude.	Same as field type
Rotation over y axis	theta	rad	fp32_t	The theta Euler angle from the vehicle’s attitude.	Same as field type
Rotation over z axis	psi	rad	fp32_t	The psi Euler angle from the vehicle’s attitude.	Same as field type
Body-Fixed xx Velocity	u	m/s	fp32_t	Body-fixed frame xx axis velocity component.	Same as field type
Body-Fixed yy Velocity	v	m/s	fp32_t	Body-fixed frame yy axis velocity component.	Same as field type
Body-Fixed zz Velocity	w	m/s	fp32_t	Body-fixed frame zz axis velocity component.	Same as field type
Ground Velocity X (North)	vx	m/s	fp32_t	Ground Velocity xx axis velocity component.	Same as field type
Ground Velocity Y (East)	vy	m/s	fp32_t	Ground Velocity yy axis velocity component.	Same as field type
Ground Velocity Z (Down)	vz	m/s	fp32_t	Ground Velocity zz axis velocity component.	Same as field type
Angular Velocity in x	p	rad/s	fp32_t	The angular velocity over body-fixed xx axis (roll).	Same as field type
Angular Velocity in y	q	rad/s	fp32_t	The angular velocity over body-fixed yy axis (pitch).	Same as field type
Angular Velocity in z	r	rad/s	fp32_t	The angular velocity over body-fixed zz axis (yaw).	Same as field type
Depth	depth	m	fp32_t	Depth, in meters. To be used by underwater vehicles. Negative values denote invalid estimates.	Same as field type
Altitude	alt	m	fp32_t	Altitude, in meters. Negative values denote invalid estimates.	Same as field type

Estimated Stream Velocity

The estimated stream velocity, typically for water or air streams.

• Abbreviation: EstimatedStreamVelocity
• Identification Number: 351
• Fixed Payload Size: 0

Name	Abbreviation	Unit	Type	Description	Range
X component (North)	x	m/s	fp64_t	X component (North).	Same as field type
Y component (East)	y	m/s	fp64_t	Y component (East).	Same as field type
Z component (Down)	z	m/s	fp64_t	Z component (Down).	Same as field type

Indicated Speed

Speed measured by the navigation filter.

• Abbreviation: IndicatedSpeed
• Identification Number: 352
• Fixed Payload Size: 0

Name	Abbreviation	Unit	Type	Description	Range
Measured speed	value	m/s	fp64_t		Same as field type

True Speed

Ground true speed.

• Abbreviation: TrueSpeed
• Identification Number: 353
• Fixed Payload Size: 0

Name	Abbreviation	Unit	Type	Description	Range
Estimated value	value	m/s	fp64_t		Same as field type

Navigation Uncertainty

Report of navigation uncertainty. This is usually given by the output of the state covariance matrix of an Extended Kalman Filter.

• Abbreviation: NavigationUncertainty
• Identification Number: 354
• Fixed Payload Size: 0

Name	Abbreviation	Unit	Type	Description	Range
Variance - x Position	x	m	fp32_t	The North offset variance of the North/East/Down field with respect to LLH.	Same as field type
Variance - y Position	y	m	fp32_t	The East offset variance of the North/East/Down field with respect to LLH.	Same as field type
Variance - z Position	z	m	fp32_t	The Down offset variance of the North/East/Down field with respect to LLH.	Same as field type
Variance - Roll	phi	rad	fp32_t	The phi Euler angle variance from the vehicle’s attitude.	Same as field type
Variance - Pitch	theta	rad	fp32_t	The theta Euler angle variance from the vehicle’s attitude.	Same as field type
Variance - Yaw	psi	rad	fp32_t	The psi Euler angle variance from the vehicle’s attitude.	Same as field type
Variance - Gyro. Roll Rate	p	rad/s	fp32_t	The angular velocity variance over body-fixed xx axis (roll).	Same as field type
Variance - Gyro. Pitch Rate	q	rad/s	fp32_t	The angular velocity variance over body-fixed yy axis (pitch).	Same as field type
Variance - Gyro. Yaw Rate	r	rad/s	fp32_t	The angular velocity variance over body-fixed zz axis (yaw).	Same as field type
Variance - Body-Fixed xx Velocity	u	m/s	fp32_t	Body-fixed frame xx axis velocity variance component.	Same as field type
Variance - Body-Fixed yy Velocity	v	m/s	fp32_t	Body-fixed frame yy axis velocity variance component.	Same as field type
Variance - Body-Fixed ww Velocity	w	m/s	fp32_t	Body-fixed frame zz axis velocity variance component.	Same as field type
Variance - Yaw Bias	bias_psi	rad	fp32_t	The psi Euler angle bias variance from the vehicle’s sensed attitude.	Same as field type
Variance - Gyro. Yaw Rate Bias	bias_r	rad/s	fp32_t	The angular velocity over body-fixed zz axis bias variance from sensor.	Same as field type

Navigation Data

Report of navigation data. This is constituted by data which is not part of the vehicle estimated state but that the user may refer for more information.

• Abbreviation: NavigationData
• Identification Number: 355
• Fixed Payload Size: 0

Name	Abbreviation	Unit	Type	Description	Range
Yaw Bias	bias_psi	rad	fp32_t	The psi Euler angle bias from the vehicle’s sensed attitude.	Same as field type
Gyro. Yaw Rate Bias	bias_r	rad/s	fp32_t	The angular velocity over body-fixed zz axis bias from sensor.	Same as field type
Course Over Ground	cog	rad	fp32_t	Course over ground given by NED ground velocity vectors.	Same as field type
Continuous Yaw	cyaw	rad	fp32_t	Continuous psi Euler angle (without normalizations).	Same as field type
GPS Rejection Filter Level	lbl_rej_level	-	fp32_t	GPS rejection filter level.	Same as field type
LBL Rejection Filter Level	gps_rej_level	-	fp32_t	LBL rejection filter level.	Same as field type
Variance - Custom Variable X	custom_x	-	fp32_t	Custom variable.	Same as field type
Variance - Custom Variable Y	custom_y	-	fp32_t	Custom variable.	Same as field type
Variance - Custom Variable Z	custom_z	-	fp32_t	Custom variable.	Same as field type

GPS Fix Rejection

No description

• Abbreviation: GpsFixRejection
• Identification Number: 356
• Fixed Payload Size: 0

Name	Abbreviation	Unit	Type	Description	Range
UTC Time of Fix	utc_time	s	fp32_t	UTC time of the rejected GPS fix measured in seconds since 00:00:00 (midnight).	Same as field type
Reason	reason	Enumerated	uint8_t	Reason for rejection.	Same as field type

LBL Range Acceptance

When the vehicle uses Long Base Line navigation, this message notifies that a new range was received from one of the acoustics transponders. The message fields are used to identify the range value and the transponder name. Also, this message has an acceptance field that indicates whether a LBL range was accepted or rejected, and if rejected, the reason why.

• Abbreviation: LblRangeAcceptance
• Identification Number: 357
• Fixed Payload Size: 0

Name	Abbreviation	Unit	Type	Description	Range
Beacon Identification Number	id	-	uint8_t	Identification number of the acoustic transponder from which the range information was received.	Same as field type
Range	range	m	fp32_t	Distance to the acoustic transponder.	Same as field type
Acceptance	acceptance	Enumerated	uint8_t	Reason for acceptance/rejection.	Same as field type

DVL Rejection

When the vehicle uses Doppler Velocity Log sensor, this message notifies that a new measurement was locally rejected by the navigation filter.

• Abbreviation: DvlRejection
• Identification Number: 358
• Fixed Payload Size: 0

Name	Abbreviation	Unit	Type	Description	Range
Type of velocity	type	Bitfield	uint8_t	This field represents the type of the rejected velocity.	Same as field type
Reason	reason	Enumerated	uint8_t	Reason for rejection. There are two types of DVL measurement filters. An Innovation filter checks the innovation between the current measurement and the previous measurement within a certain amount of time and an Absolute filter compares the measurement with an absolute threshold value. Those filters are tested using horizontal speed measurements, i.e., measurements in the x-axis and in the y-axis.	Same as field type
Value	value	m/s	fp32_t	Value of the rejection. If it is an innovation rejection the value is the absolute difference between the previous accepted DVL measurement and the current one. If it is an absolute rejection the value is the current DVL measurement.	Same as field type
Timestep	timestep	s	fp32_t	Timestep of the rejection. The timestep is 0 for an absolute rejection since it is an instantaneous reading. For innovation rejection it is the time difference between the previous accepted DVL measurement and the current one.	Same as field type

Navigation Reset

Request a navigation reset.

• Abbreviation: NavigationReset
• Identification Number: 359
• Fixed Payload Size: 0

This message has no fields.

LBL Beacon Position Estimate

LBL Beacon position estimate.

• Abbreviation: LblEstimate
• Identification Number: 360
• Fixed Payload Size: 0

Name	Abbreviation	Unit	Type	Description	Range
Beacon Name	beacon	-	plaintext	Name/Label of the acoustic transponder.	Same as field type
North position	x	m	fp64_t	The North offset of the North/East/Down field.	Same as field type
East position	y	m	fp64_t	The East offset of the North/East/Down field.	Same as field type
Depth	depth	m	fp32_t	The beacon’s depth.	Same as field type
North position variance	var_x	m	fp64_t	The North offset variance of the North/East/Down field with respect to LLH.	Same as field type
East position variance	var_y	m	fp64_t	The East offset variance of the North/East/Down field with respect to LLH.	Same as field type

Alignment State

This message notifies the vehicle is ready for dead-reckoning missions.

• Abbreviation: AlignmentState
• Identification Number: 361
• Fixed Payload Size: 0

Name	Abbreviation	Unit	Type	Description	Range
State	state	Enumerated	uint8_t	Alignment State.	Same as field type