Communication & Messaging

1. Interfacing

The communication interfaces currently supported for the ANELLO Aerial INS:

  1. Serial (RS-232)

  2. UDP (Ethernet)

  3. CAN (NMEA 2000)

1.1 Serial Communication Parameters

Default Baud Rate:

  • RS-232-1: 57600

  • RS-232-2: 921600 units shipped prior to 2/19/2026 have a default baud rate of 57600

The maximum supported baud rate for both serial ports is 921600

Data Format

  • Data Bits: 8

  • Stop Bits: 1

  • Parity: None

1.2 Port Definitions

Interface

Supported Protocols

Default Configuration

Functions

RS232-1

Serial, MAVLink, NMEA 0183

MAVLink at 57600

Data input / output, configuration, firmware updates

RS232-2

Serial, MAVLink, NMEA 0183

NMEA 0183 at 921600

Data input / output, configuration

Ethernet

UDP, MAVLink, NMEA 0183

MAVLink (UDP 14550)

Data input / output, configuration, log downloads

CAN

NMEA 2000

NMEA 2000

Data input / output

1.3 Time Synchronization

The ANELLO Aerial INS supplies the following I/O pins for time synchronization

Interface

Max Voltage

Functions

PPS

3.3 V

GNSS time synchronization output pulse

Sync

3.3 V

GNSS time synchronization input pulse

Reset

3.3 V

Driving low restarts the Aerial INS

See Mechanicals to find the specified output pins.

2. Input Messages

2.1 NMEA 0183 Input Messages

The ANELLO Aerial INS supports standard NMEA 0183 input messages which allow the UAV to send in external sensor information, e.g. for speed-aiding. ANELLO also has a set of proprietary messages, following the standard NMEA proprietary format with a prefix of “$P”, company code of “AP” (ANELLO Photonics), and the message code.

To configure NMEA 0183 over a serial port, update the following configs (see Configure ANELLO Aerial INS for instructions on changing settings):

NM0183_CFG = 1 (RS232-1) or 2 (RS232-2)

To change the baud rate use SER_TEL1_BAUD for RS232-1 or SER_TEL2_BAUD for RS232-2.

For the full table of serial NMEA0183 parameters, see NMEA0183 Serial Parameters.

To configure NMEA 0183 over UDP, update the following configs (see Configure ANELLO Aerial INS for instructions on changing settings):

NMUDP_EN = 1

UDP input uses port 19551 and UDP output uses port 19550. External UDP output only occurs when NMUDP_MC_IP0 through NMUDP_MC_IP3 define a valid multicast group. Setting NMUDP_EN to 1 alone does not produce external UDP output.

See NMEA0183 over UDP Parameters for the full parameter table.

2.1.1 External Sensor Aiding

2.1.1.1. VHW: Water Speed & Heading

Message Format:

$--VHW,x.x,T,x.x,M,x.x,N,x.x,K*hh

Index

Part

Description

1

x.x

True Heading, Degrees

2

T

T = True

3

x.x

Magnetic Heading, Degrees

4

M

M = Magnetic

5

x.x

Knots (speed of vessel relative to the water)

6

N

N = Knots

7

x.x

Kilometers per hour (speed of vessel relative to the water)

8

K

K = Kilometres per hour

9

hh

Checksum

Note

Aerial INS uses fields 1, 3, 5, and 7 from this sentence.

2.1.1.2. VBW: Dual Ground/Water Speed

Message Format:

$--VBW,x.x,x.x,A,x.x,x.x,A*hh

Index

Part

Description

1

x.x

Longitudinal water speed, “-“ means astern

2

x.x

Transverse water speed, “-“ means port

3

A

Status, A = Data Valid

4

x.x

Longitudinal ground speed, “-“ means astern

5

x.x

Transverse ground speed, “-“ means port

6

A

Status, A = Data Valid

7

hh

Checksum

Note

Aerial INS uses fields 1 through 6 from this sentence.

2.1.2 External Position Aiding

To enable external NMEA0183 GNSS input set EKF2_GPS_EXT_EN = 1 or Enabled

To enable a secondary input-only serial port to receive external NMEA0183 GNSS input set NM_GNSS_CFG = 1 (RS232-1) or 2 (RS232-2)

To use an external GNSS input, the minimum required messages are GGA, RMC, and GSA at a rate of at least 0.5 Hz. In order for the algorithm to use external GNSS updates, RMC must report status = A, latitude and longitude must be valid, GSA mode must be 3 or greater, and PDOP, HDOP, and VDOP must all be present, finite, and greater than zero.

See External Position Aiding Parameters for the parameter table used to configure external position aiding. See Configure ANELLO Aerial INS for instructions on changing settings.

2.1.2.2. GGA: Global Positioning System Fix Data

Message Format:

$--GGA,hhmmss.ss,ddmm.mmmmmm,a,dddmm.mmmmmm,a,x,xx,x.x,x.x,M,x.x,M,x.x,xxxx*hh

Index

Part

Description

1

hhmmss.ss

Time (UTC)

2

ddmm.mmmmmm

Latitude

3

a

N or S

4

dddmm.mmmmmm

Longitude

5

a

E or W

6

x

GPS Quality Indicator (see table below)

7

xx

Number of satellites in use (00-12)

8

x.x

Horizontal Dilution of Precision (HDOP)

9

x.x

Altitude (MSL)

10

M

Units of altitude (M=Meters)

11

x.x

Geoidal separation

12

M

Units of geoidal separation (M=Meters)

13

x.x

Age of differential data (seconds)

14

xxxx

Differential Reference Station ID (0000-1023)

15

hh

Checksum

Note

Aerial INS uses fields 1 through 9 and field 11 from this sentence.

GPS Quality Indicator

Value

Description

0

Fix not available or invalid

1

GPS fix (no corrections)

2

Differential GPS fix

4

RTK Fixed

5

RTK Float

6

Dead reckoning mode (GPS is determined to be jammed or spoofed)
2.1.2.3. GSA: GNSS DOP and Active Satellites

Message Format:

$--GSA,a,x,xx,xx,xx,xx,xx,xx,xx,xx,xx,xx,xx,xx,xx,x.x,x.x,x.x*hh

Index

Part

Description

1

a

Mode 1: M = Manual, A = Automatic

2

x

Mode 2: Fix Type (1 = No Fix, 2 = 2D Fix, 3 = 3D Fix)

3

xx

Satellite ID used for fix (PRN #1)

4

xx

Satellite ID used for fix (PRN #2)

5

xx

Satellite ID used for fix (PRN #3)

6

xx

Satellite ID used for fix (PRN #4)

7

xx

Satellite ID used for fix (PRN #5)

8

xx

Satellite ID used for fix (PRN #6)

9

xx

Satellite ID used for fix (PRN #7)

10

xx

Satellite ID used for fix (PRN #8)

11

xx

Satellite ID used for fix (PRN #9)

12

xx

Satellite ID used for fix (PRN #10)

13

xx

Satellite ID used for fix (PRN #11)

14

xx

Satellite ID used for fix (PRN #12)

15

x.x

PDOP (Position Dilution of Precision)

16

x.x

HDOP (Horizontal Dilution of Precision)

17

x.x

VDOP (Vertical Dilution of Precision)

18

hh

Checksum

Note

Aerial INS uses fields 1 through 17 from this sentence. The real-time algorithm relies on fields 2, 15, 16, and 17.

2.1.3 ANELLO Proprietary

2.1.3.1. GPSCTRL: GPS Control (ANELLO Proprietary)

Enables or disables GPS utilization in sensor fusion algorithm.

Message Format:

$PAPGPSCTRL,A*hh

Index

Part

Description

1

A

GPS control, “1” = Use GPS (default), “0” = Ignore GPS

2

hh

Checksum

Note

Aerial INS uses field 1 from this sentence.

2.1.3.2. AUTOCAL: Speed Sensor Auto-Calibration Control (ANELLO Proprietary)

This message starts/stops the Aerial INS speed sensor auto-calibration routine (e.g., for water-speed aiding sensors). The default state is 0 (not in auto-calibration mode).

Message Format:

$PAPAUTOCAL,A*hh

Index

Part

Description

1

A

Auto-calibration control: “0” = Off (default), “1” = On (enter auto-cal)

2

hh

Checksum

Note

Aerial INS uses field 1 from this sentence.

Recommended data collection procedure (while x = 1)

  • Operate in calm waters with minimal currents/wind/wake.

  • Run out-and-back legs along the same line (reciprocal headings).

  • Collect data at ≥ 5 different steady speeds spanning the full operating speed range.

  • Each out leg and back leg should be at least 30 seconds at a steady speed.

  • Repeat each speed at least once (more repeats improves robustness), and avoid aggressive turns during the steady legs.

  • When complete, send $PAPAUTOCAL,0*hh to exit auto-calibration mode.

2.1.3.3. PAPPOS: Auxiliary Position (Lat/Lon/Alt) (ANELLO Proprietary)

This message can be used to pass in an external position, either from user input or an external aiding source such as visual waypoint detection, USBL acoustic positioning, star tracker, or an M Code receiver.

Message Format:

$PAPPOS,hhmmss.ss,PX,PY,PZ,H_acc,V_acc*hh

Index

Part

Description

1

hhmmss.ss

UTC time field. This field may be left empty, but the comma position is required.

2

PX

Latitude in degrees (signed; +N / -S)

3

PY

Longitude in degrees (signed; +E / -W)

4

PZ

Altitude above mean sea level (meters)

5

H_acc

Horizontal accuracy / uncertainty (meters)

6

V_acc

Vertical accuracy / uncertainty (meters)

7

hh

NMEA checksum (hex)

Note

Aerial INS uses fields 2 through 6 from this sentence.

2.1.3.4. PAPRPH: Roll/Pitch/Heading (with Accuracies) (ANELLO Proprietary)

This message can be used to pass in an external heading, either from user input or an external aiding source such as a well-calibrated magnetometer, star tracker, or an M Code receiver. Currently only external heading aiding is implemented, and roll/pitch aiding are available upon request.

Message Format:

$PAPRPH,hhmmss.ss,R,P,Y,R_acc,P_acc,H_acc*hh

Index

Part

Description

1

hhmmss.ss

UTC time field. This field may be left empty, but the comma position is required.

2

R

Roll angle (degrees)

3

P

Pitch angle (degrees)

4

Y

Heading / yaw (degrees, typically 0..360)

5

R_acc

Roll accuracy / uncertainty (degrees)

6

P_acc

Pitch accuracy / uncertainty (degrees)

7

H_acc

Heading accuracy / uncertainty (degrees)

8

hh

NMEA checksum (hex)

Note

Aerial INS uses fields 2 through 7 from this sentence.

2.2 NMEA 2000 Input Messages

The ANELLO Aerial INS also supports the following standard NMEA 2000 input messages, which allow the vehicle to send in external sensor information, e.g. for speed-aiding.

Ensure NM2K_CFG is set to 1 before using the NMEA 2000 driver on the CAN port. This enables the driver and allows the system to publish and receive NMEA 2000 messages.

2.2.1 PGN 127488: Engine Parameters, Rapid Update

Provides data with a high update rate for a specific engine in a single frame message.

#

Field

Description

Unit

Type

1

Engine Instance

Identifies the specific engine (0=Single)

8-bit unsigned

2

Engine Speed

Engine rotational speed

RPM

16-bit unsigned

3

Engine Boost Pressure

Turbocharger or supercharger pressure

kPa

16-bit signed

4

Engine Tilt/Trim

Engine tilt or trim position

%

8-bit signed

Note

Aerial INS uses fields 1 through 4 from this PGN.

Logged topic: NMEA2000_ENGINE

2.2.2 PGN 127489: Engine Parameters, Dynamic

Provides real-time operational data and status for a specific engine, usually broadcast periodically for control or instrumentation.

#

Field

Description

Unit

Type

1

Engine Instance

Identifies the specific engine (0=Single)

8-bit unsigned

2

Engine Oil Pressure

Engine lubricant pressure

kPa

16-bit unsigned

3

Engine Oil Temperature

Temperature of the engine lubricant

K

16-bit unsigned

4

Engine Temperature

Temperature of the engine coolant

K

16-bit unsigned

5

Alternator Potential

Alternator output voltage

V

16-bit signed

6

Fuel Rate

Engine fuel consumption rate

L/hr

16-bit signed

7

Total Engine Hours

Cumulative operating time of the engine

s

32-bit unsigned

8

Engine Coolant Pressure

Pressure of the engine coolant

kPa

16-bit unsigned

9

Fuel Pressure

Pressure of the fuel

kPa

16-bit unsigned

10

Engine Discrete Status 1

Bitmask indicating warnings and statuses

16-bit bitmap

11

Engine Discrete Status 2

Bitmask indicating other statuses

16-bit bitmap

12

Percent Engine Load

Current power output as a percentage of max

%

8-bit unsigned

13

Percent Engine Torque

Current torque output as a percentage of max

%

8-bit signed

Note

Aerial INS uses fields 1 through 13 from this PGN. Fields 10 and 11 are logged as raw bitmaps.

Logged topic: NMEA2000_ENGINE_DYN

2.2.3 PGN 128259: Speed, Water Referenced

Provides a single transmission describing the motion of a vessel relative to the water.

#

Field

Description

Unit

Type

1

SID

Sequence Identifier

8-bit unsigned

2

Speed Water Referenced

Vessel’s speed relative to the water

m/s

16-bit signed

3

Speed Ground Referenced

Vessel’s speed relative to the ground (SOG)

m/s

16-bit signed

4

Speed Water Referenced Type

Method of measurement (e.g., Paddle wheel)

8-bit lookup

5

Speed Direction

Direction of water-referenced speed

4-bit unsigned

Note

Aerial INS uses fields 1 through 5 from this PGN. Fields 4 and 5 are used without remapping.

Logged topic: NMEA2000_SPEED

2.2.4 PGN 128275: Distance Log

Cumulative voyage distance traveled since last reset, tagged with time and date.

#

Field

Description

Unit

Type

1

Date

Days since January 1, 1970

d

16-bit unsigned

2

Time

Seconds since midnight

s

32-bit unsigned

3

Total Cumulative Distance

Total distance traveled through water

m

32-bit unsigned

4

Distance Since Last Reset

Distance traveled since last reset

m

32-bit unsigned

Note

Aerial INS uses fields 1 through 4 from this PGN.

Logged topic: NMEA2000_DISTANCE

2.2.5 PGN 130311: Environmental Parameters

These values provide weather and ambient condition data, often used for sensor calibration, navigation adjustments, and environmental awareness.

#

Field

Description

Unit

Type

1

SID

Sequence Identifier

8-bit unsigned

2

Temperature Source

Source of the temperature reading

6-bit lookup

3

Humidity Source

Source of the humidity reading

2-bit lookup

4

Temperature

Actual temperature reading

K

16-bit signed

5

Humidity

Relative humidity

%

16-bit signed

6

Atmospheric Pressure

Barometric pressure

Pa

16-bit unsigned

Note

Aerial INS uses fields 1 through 6 from this PGN. Fields 2 and 3 are used without remapping.

Logged topic: NMEA2000_ENVIRONMENT

2.2.6 PGN 130578: Vessel Speed Components

Accurately describes the speed of a vessel by component vectors.

#

Field

Description

Unit

Type

1

Longitudinal Speed, Water-referenced

Forward/aft speed relative to water (surge)

m/s

16-bit signed

2

Transverse Speed, Water-referenced

Port/starboard speed relative to water (sway)

m/s

16-bit signed

3

Longitudinal Speed, Ground-referenced

Forward/aft speed relative to ground

m/s

16-bit signed

4

Transverse Speed, Ground-referenced

Port/starboard speed relative to ground

m/s

16-bit signed

5

Stern Speed, Water-referenced

Transverse speed of the stern relative to water

m/s

16-bit signed

6

Stern Speed, Ground-referenced

Transverse speed of the stern relative to ground

m/s

16-bit signed

Note

Aerial INS uses fields 1 through 6 from this PGN.

Logged topic: NMEA2000_VESSEL_SPEED

2.2.7 PGN 61184: GPS Control

ANELLO proprietary message used to enable or disable the GPS through the NMEA2000 interface. CAN ID format: 0x18EF<dest><src>

#

Field

Description

Unit

Type

1

GPS Control

GPS enable/disable command: 0 = Disable GPS, 1 = Enable GPS

8-bit unsigned

Note

Maritime INS uses field 1 from this PGN.

Logged topic: NMEA2000_GPSCTRL

2.2.8 PGN 126720: Speed Sensor Auto-Calibration Control (ANELLO Proprietary)

ANELLO proprietary NMEA 2000 message used to start/stop the speed sensor auto-calibration routine. The default state is 0 (not in auto-calibration mode). CAN ID format: 0x19EF<dest><src>

Field

Name

Description

Unit

Type

1

Auto-calibration Control

0 = Off (default), 1 = On (enter auto-calibration mode)

8-bit unsigned

Recommended data collection procedure (while Auto-calibration Control = 1)

  • Operate in calm waters with minimal currents/wind/wake.

  • Run out-and-back legs on reciprocal headings.

  • Use ≥ 5 steady speeds spanning your full speed range.

  • Hold each leg ≥ 30 seconds at steady speed.

  • Exit auto-calibration by transmitting Auto-calibration Control = 0.

Note

Aerial INS uses field 1 from this PGN.

Logged topic: NMEA2000_AUTOCAL_WATERSPEED

2.2.9 PGN 127493: Transmission Parameters, Dynamic

Provides real-time operational data and status for a specific transmission, typically broadcast periodically for monitoring and instrumentation.

#

Field

Description

Unit

Type

1

Transmission Instance

Identifies the specific transmission instance

8-bit unsigned

2

Gear*

Current transmission gear state

2-bit unsigned

3

Reserved

Reserved for future use

6-bit unsigned

4

Oil Pressure

Transmission oil pressure

kPa

16-bit unsigned

5

Oil Temperature

Transmission oil temperature

K

16-bit unsigned

6

Transmission Status

Bitmask indicating transmission status

8-bit bitmap

7

Reserved

Reserved for future use

8-bit unsigned

Gear Status (2-bit value)

Value

Description

0

Forward

1

Neutral

2

Reverse

3

Reserved

Note

Aerial INS uses fields 1, 2, 4, 5, and 6 from this PGN. Field 6 is logged as a raw bitmap.

Logged topic: NMEA2000_TRANSMISSION

2.2.10 PGN 130816: Auxiliary Position (ANELLO Proprietary)

Auxiliary GPS / GNSS position information input

#

Field

Description

Unit

Type

1

lat

Latitude

deg

32-bit signed

2

lon

Longitude

deg

32-bit signed

3

alt

Altitude above mean sea level

m

32-bit signed

4

hacc

Horizontal accuracy / uncertainty

m

32-bit signed

5

vacc

Vertical accuracy / uncertainty

m

32-bit signed

Note

Aerial INS uses fields 1 through 5 from this PGN. Latitude and longitude are encoded as 1e-7 deg/count. Altitude is encoded as 1e-3 m/count. Horizontal accuracy and vertical accuracy are encoded as 1e-7 m/count.

Logged topic: NMEA2000_POS

2.2.11 PGN 130817: Auxiliary Attitude (ANELLO Proprietary)

Auxiliary roll, pitch, and heading information along with accuracy estimates

#

Field

Description

Unit

Type

1

roll

Roll angle

deg

32-bit signed

2

pitch

Pitch angle

deg

32-bit signed

3

heading

Heading / yaw

deg

32-bit signed

4

roll_acc

Roll accuracy / uncertainty

deg

32-bit signed

5

pitch_acc

Pitch accuracy / uncertainty

deg

32-bit signed

6

head_acc

Heading accuracy / uncertainty

deg

32-bit signed

Note

Aerial INS uses fields 1 through 6 from this PGN. All fields are encoded as 1e-7 deg/count.

Logged topic: NMEA2000_RPH

3. Output Messages

3.1 NMEA 0183 Output Messages

To configure NMEA 0183 over a serial port, update the following configs (see Configure ANELLO Aerial INS for instructions on changing settings):

  • NM0183_CFG = 1 (RS232-1) or 2 (RS232-2)

  • NM0183_ODR_GGA = 5 (output data rate; e.g. 5 = 5 Hz, 0 is no output)

  • NM0183_ODR_RMC = 5 (output data rate; e.g. 5 = 5 Hz, 0 is no output)

  • NM0183_ODR_VTG = 5 (output data rate; e.g. 5 = 5 Hz, 0 is no output)

  • NM0183_ODR_GSA = 5 (output data rate; e.g. 5 = 5 Hz, 0 is no output)

  • NM0183_ODR_GSV = 5 (output data rate; e.g. 5 = 5 Hz, 0 is no output)

  • NM0183_ODR_APIMU = 5 (output data rate; e.g. 5 = 5 Hz, 0 is no output)

  • NM0183_ODR_APINS = 5 (output data rate; e.g. 5 = 5 Hz, 0 is no output)

The default baud rate is 57600 for RS232-1 and 921600 for RS232-2. Units shipped prior to 2/19/2026 have a default baud rate of 57600 on both ports. To change the baud rate use SER_TEL1_BAUD for RS232-1 or SER_TEL2_BAUD for RS232-2.

To configure NMEA 0183 over UDP, update the following configs (see Configure ANELLO Aerial INS for instructions on changing settings):

  • NMUDP_EN = 1

  • NMUDP_ODR_GGA = 5 (output data rate; e.g. 5 = 5 Hz, 0 is no output)

  • NMUDP_ODR_RMC = 5 (output data rate; e.g. 5 = 5 Hz, 0 is no output)

  • NMUDP_ODR_VTG = 5 (output data rate; e.g. 5 = 5 Hz, 0 is no output)

  • NMUDP_ODR_GSA = 5 (output data rate; e.g. 5 = 5 Hz, 0 is no output)

  • NMUDP_ODR_GSV = 5 (output data rate; e.g. 5 = 5 Hz, 0 is no output)

  • NMUDP_ODR_APIMU = 5 (output data rate; e.g. 5 = 5 Hz, 0 is no output)

  • NMUDP_ODR_APINS = 5 (output data rate; e.g. 5 = 5 Hz, 0 is no output)

UDP output uses port 19550 and UDP input uses port 19551. External UDP output only occurs when NMUDP_MC_IP0 through NMUDP_MC_IP3 define a valid multicast group. Setting NMUDP_EN to 1 alone does not produce external UDP output.

See NMEA0183 over UDP Parameters for how to set the multicast IP.

3.1.1. RMC: Recommended Minimum Navigation Information

Message Format:

$--RMC,hhmmss.ss,A,ddmm.mmmmmm,a,dddmm.mmmmmm,a,x.x,x.x,xxxx,x.x,a*hh

Index

Part

Description

1

hhmmss.ss

Time (UTC)

2

A

Status, A = solution initialized, V = Void, solution (position and/or heading) not initialized

3

ddmm.mmmmmm

Latitude

4

a

N or S

5

dddmm.mmmmmm

Longitude

6

a

E or W

7

x.x

Speed over ground, knots

8

x.x

Course over ground, degrees (range from 0 to 360)

9

xxxx

Date, ddmmyy

10

x.x

Magnetic Variation, degrees

11

a

E or W

12

hh

Checksum

Note

Fields 10 and 11 are left blank in current Aerial INS output.

3.1.2. GGA: Global Positioning System Fix Data

Message Format:

$--GGA,hhmmss.ss,ddmm.mmmmmm,a,dddmm.mmmmmm,a,x,xx,x.x,x.x,M,x.x,M,x.x,xxxx*hh

Index

Part

Description

1

hhmmss.ss

Time (UTC)

2

ddmm.mmmmmm

Latitude

3

a

N or S

4

dddmm.mmmmmm

Longitude

5

a

E or W

6

x

GPS Quality Indicator (see table below)

7

xx

Number of satellites in use (00-12)

8

x.x

Horizontal Dilution of Precision (HDOP)

9

x.x

Altitude (MSL)

10

M

Units of altitude (M=Meters)

11

x.x

Geoidal separation

12

M

Units of geoidal separation (M=Meters)

13

x.x

Age of differential data (seconds)

14

xxxx

Differential Reference Station ID (0000-1023)

15

hh

Checksum

GPS Quality Indicator

Value

Description

0

Fix not available or invalid

1

GPS fix (no corrections)

2

Differential GPS fix

4

RTK Fixed

5

RTK Float

6

Dead reckoning mode (GPS is determined to be jammed or spoofed)

3.1.3. VTG: Course Over Ground and Ground Speed

Message Format:

$--VTG,x.x,T,x.x,M,x.x,N,x.x,K,a*hh

Index

Part

Description

1

x.x

Course over ground, degrees true

2

T

True course indicator

3

x.x

Course over ground, degrees magnetic

4

M

Magnetic course indicator

5

x.x

Speed over ground, knots

6

N

Knots speed indicator

7

x.x

Speed over ground, kilometers per hour

8

K

Kilometers-per-hour speed indicator

9

a

Mode indicator

10

hh

Checksum

3.1.4. GSA: GNSS DOP and Active Satellites

Message Format:

$--GSA,a,x,xx,xx,xx,xx,xx,xx,xx,xx,xx,xx,xx,xx,xx,x.x,x.x,x.x*hh

Index

Part

Description

1

a

Mode 1: M = Manual, A = Automatic

2

x

Mode 2: Fix Type (1 = No Fix, 2 = 2D Fix, 3 = 3D Fix)

3

xx

Satellite ID used for fix (PRN #1)

4

xx

Satellite ID used for fix (PRN #2)

5

xx

Satellite ID used for fix (PRN #3)

6

xx

Satellite ID used for fix (PRN #4)

7

xx

Satellite ID used for fix (PRN #5)

8

xx

Satellite ID used for fix (PRN #6)

9

xx

Satellite ID used for fix (PRN #7)

10

xx

Satellite ID used for fix (PRN #8)

11

xx

Satellite ID used for fix (PRN #9)

12

xx

Satellite ID used for fix (PRN #10)

13

xx

Satellite ID used for fix (PRN #11)

14

xx

Satellite ID used for fix (PRN #12)

15

x.x

PDOP (Position Dilution of Precision)

16

x.x

HDOP (Horizontal Dilution of Precision)

17

x.x

VDOP (Vertical Dilution of Precision)

18

hh

Checksum

3.1.5. GSV: GNSS Satellites in View

Message Format:

$--GSV,x,x,xx,xx,xx,xxx,xx,xx,xx,xxx,xx,xx,xx,xxx,xx,xx,xx,xxx,xx*hh

Index

Part

Description

1

x

Total number of GSV messages for this epoch

2

x

Message number

3

xx

Total number of satellites in view

4

xx

Satellite ID (PRN #1 in this message)

5

xx

Elevation, degrees (satellite #1)

6

xxx

Azimuth, degrees true (satellite #1)

7

xx

Signal-to-noise ratio, dB-Hz (satellite #1)

8-11

xx

Satellite ID, elevation, azimuth, and SNR for satellite #2

12-15

xx

Satellite ID, elevation, azimuth, and SNR for satellite #3

16-19

xx

Satellite ID, elevation, azimuth, and SNR for satellite #4

20

hh

Checksum

3.1.6 IMU: Proprietary IMU Output

Message Format:

$PAPIMU,Time,T_Sync,AX,AY,AZ,WX,WY,WZ,OG_WX,OG_WY,OG_WZ,MAG_X,MAG_Y,MAG_Z,TempC,Status_X,Status_Y,Status_Z*hh

Index

Field

Units

Description

1

Time

ms

Time since power on

2

T_Sync

ms

IMU synchronization timestamp

3

AX

g

X-Axis Acceleration

4

AY

g

Y-Axis Acceleration

5

AZ

g

Z-Axis Acceleration

6

WX

deg/s

X-Axis Angular Rate (MEMS)

7

WY

deg/s

Y-Axis Angular Rate (MEMS)

8

WZ

deg/s

Z-Axis Angular Rate (MEMS)

9

OG_WX

deg/s

High Precision X-Axis Angular Rate (ANELLO Optical Gyro)

10

OG_WY

deg/s

High Precision Y-Axis Angular Rate (ANELLO Optical Gyro)

11

OG_WZ

deg/s

High Precision Z-Axis Angular Rate (ANELLO Optical Gyro)

12

MAG_X

Gauss

X-Axis Magnetic Field Measurement

13

MAG_Y

Gauss

Y-Axis Magnetic Field Measurement

14

MAG_Z

Gauss

Z-Axis Magnetic Field Measurement

15

TempC

°C

Temperature

16

Status_X

Status bitfield for X-axis SiPhOG (see table below)

17

Status_Y

Status bitfield for Y-axis SiPhOG (see table below)

18

Status_Z

Status bitfield for Z-axis SiPhOG (see table below)

APIMU Status Bits

Bit

Meaning

0

Reserved in current Aerial INS output and always 0

1

Temperature uncontrolled

2

Over-current error

3

SiPhOG supply-voltage error

4-7

Unused and always 0

3.1.7 INS: Proprietary Navigation Output

Message Format:

$PAPINS,Time,PPS_Time,Status,Lat,Long,Height,VN,VE,VD,Roll,Pitch,Heading,Reserved*hh

Index

Field

Units

Description

1

Time

ms

Time since power on

2

PPS Time

ns

Currently always 0.000

3

Status

Navigation status code (see table below)

4

Lat

deg

Latitude, + = North, - = South

5

Long

deg

Longitude, + = East, - = West

6

Height

m

Height above ellipsoid

7

VN

m/s

North velocity in NED frame

8

VE

m/s

East velocity in NED frame

9

VD

m/s

Down velocity in NED frame

10

Roll

deg

Roll angle about body X

11

Pitch

deg

Pitch angle about body Y

12

Heading

deg

Heading angle about body Z

13

Reserved

Currently emitted empty

APINS Status Values

Value

Meaning

0

Attitude only using internal GNSS selection

1

Position and attitude using internal GNSS selection

2

Position, attitude, and heading using internal GNSS selection

8

Attitude only with GPS commanded off by the user

9

Position and attitude with GPS commanded off by the user

10

Position, attitude, and heading with GPS commanded off by the user

15

Position and attitude while external GNSS is selected

16

Position, attitude, and heading while external GNSS is selected

20

Dead reckoning after GNSS loss following prior GNSS fusion

3.2 NMEA 2000 Output Messages

Ensure NM2K_CFG is set to 1 before using the NMEA 2000 driver on the CAN port. This enables the driver and allows the system to publish and receive NMEA 2000 messages.

Each published PGN has an associated output data rate parameter (for example, NM2K_129025_RATE, NM2K_129026_RATE, NM2K_129029_RATE) within the NMEA2000 parameter group. Rates are specified in Hertz, clamped to the range 0–100; setting a rate to 0 disables that PGN.

3.2.1 PGN 129025: Position, Rapid Update

High-speed update of vessel latitude/longitude position.

#

Field

Description

Unit

Type

1

Latitude

Position latitude

deg

32-bit signed

2

Longitude

Position longitude

deg

32-bit signed

Note

Current Aerial INS output encodes latitude and longitude as 1e-7 deg/count.

3.2.2 PGN 129026: COG & SOG, Rapid Update

Rapid update of Course Over Ground (COG) and Speed Over Ground (SOG).

#

Field

Description

Unit

Type

1

SID

Sequence Identifier

8-bit unsigned

2

COG Reference

True/Magnetic reference

2-bit lookup

3

COG

Course over ground

rad

16-bit unsigned

4

SOG

Speed over ground

m/s

16-bit unsigned

Note

Current Aerial INS output sets field 2 to 0.

3.2.3 PGN 129029: GNSS Position Data

Complete GNSS navigation solution including position, quality, and DOP.

#

Field

Description

Unit

Type

1

SID

Sequence Identifier

8-bit unsigned

2

Date

Days since 1970-01-01

days

16-bit unsigned

3

Time

Seconds since midnight

s

32-bit unsigned

4

Latitude

GNSS latitude (WGS-84)

deg

64-bit signed

5

Longitude

GNSS longitude (WGS-84)

deg

64-bit signed

6

Altitude

Altitude referenced to WGS-84

m

64-bit signed

7

GNSS Type

GPS, GLONASS, Galileo, BeiDou, etc.

4-bit lookup

8

Method

No fix, RTK, etc. (see table below)

4-bit lookup

9

Integrity

Integrity flag

2-bit lookup

10

Reserved

Reserved (transmit as 0)

6 bits reserved

11

Number of SVs

Number of satellites used in solution

8-bit unsigned

12

HDOP

Horizontal dilution of precision

16-bit signed

13

PDOP

Positional dilution of precision

16-bit signed

14

Geoidal Separation

Geoid–ellipsoid separation

m

32-bit signed

15

Reference Stations

Number of reference stations

8-bit unsigned

16

Reference Station Type

Type for reference station #1

4-bit lookup

17

Reference Station ID

ID for reference station #1

12-bit unsigned

18

Age of DGNSS Corrections

Age of corrections for station #1

s

16-bit signed

Note

Current Aerial INS output sets field 7 to 0, field 9 to 0, field 15 to 1, and field 16 to 6. Field 17 comes from the GNSS reference ID. Latitude and longitude are encoded as 1e-16 deg/count. Altitude is encoded as 1e-6 m/count.

Method Field Values (4-bit lookup):

Value

Meaning

0

No GNSS (no valid fix)

1

GNSS Fix (standard 2D/3D)

2

DGNSS (differential fix)

3

Precise GNSS

4

RTK Fixed Integer

5

RTK Float

6

Estimated (dead reckoning)

7

Manual Input

8

Simulation Mode

15

Invalid

Note

Current Aerial INS output uses field 8 for the reported GNSS method.

3.2.4 PGN 127250: Vessel Heading

Provides vessel heading and related status.

#

Field

Description

Unit

Type

1

SID

Sequence Identifier

8-bit unsigned

2

Heading

Vessel heading

rad

16-bit unsigned

3

Deviation

Magnetic deviation

rad

16-bit signed

4

Variation

Magnetic variation

rad

16-bit signed

5

Reference

True/Magnetic

2-bit lookup

Note

Current Aerial INS output sets field 5 to 0.

3.2.5 PGN 127251: Rate of Turn

Provides vessel rate of turn information.

#

Field

Description

Unit

Type

1

SID

Sequence Identifier

8-bit unsigned

2

Rate of Turn

Positive = turn to starboard

rad/s

32-bit signed

3.2.6 PGN 127257: Attitude

Provides vessel orientation (roll, pitch, yaw).

#

Field

Description

Unit

Type

1

SID

Sequence Identifier

8-bit unsigned

2

Yaw

Vessel yaw angle

rad

16-bit signed

3

Pitch

Vessel pitch angle

rad

16-bit signed

4

Roll

Vessel roll angle

rad

16-bit signed

Note

Current Aerial INS output encodes yaw, pitch, and roll as 1e-4 rad/count.

3.2.7 PGN 126992: System Time

Provides system time for network synchronization.

#

Field

Description

Unit

Type

1

SID

Sequence Identifier

8-bit unsigned

2

Source

Time source (GPS, RTC, etc.)

8-bit lookup

3

Date

Days since 1970-01-01

16-bit unsigned

4

Time

Seconds since midnight

s

32-bit unsigned

Note

Current Aerial INS output sets field 2 to 0.