Garmin GNX 21, Owner'S Manual

NMEA 0183 Data Type Information

Each NMEA certified sensor provides unique information to the 

NMEA certified display device, such as the GNX 20/21. The 

data you can view on your display depends on the sensors you 

have installed and configured. See the General NMEA Data 

Type Requirements topic in the 

Technical Reference for 

Garmin® NMEA Products

 manual at 

www.garmin.com/support

.

Registering Your Device

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Appendix

Data Fields

ABS

: Absolute, relative to another data field. For example, 

absolute humidity.

AIR

: The air temperature.

AVG

: The average amount.

AWA

: The wind angle measured relative to the bow of the 

vessel.

AWS

: The measured speed of the wind.

BAR

: The calibrated current pressure.

BAT

: The battery voltage.

BTW

: The direction from your current location to a destination. 

You must be navigating for this data to appear.

COG

: The actual direction of travel, regardless of the course 

steered and temporary variations in heading.

CTS

: The direction in which you must steer to return to the 

course set at the start of navigation.

DIS

: The distance traveled for the current track or activity.

DPT

: The depth of the water. Your device must be connected to 

a NMEA 0183 or NMEA 2000 device capable of acquiring 

the water depth.

DRF

: The speed of the current.

DTW

: The distance to the waypoint.

ELV

: The altitude of your current location above or below sea 

level.

ERR

: The precision of the current position, when used with 

GPS.

GWD

: The direction of the wind relative to the ground, 

referenced from the north. 

GWS

: The speed of the wind relative to the ground.

HDG

: The direction the boat is pointing.

HUM

: The level of humidity.

MAX

: The maximum in relation to another data field. For 

example, maximum speed.

MIN

: The minimum in relation to another data field. For 

example, minimum speed.

ODO

: A running tally of distance traveled for all trips. This total 

does not clear when resetting the trip data.

OTH

: The opposite tack direction of the vessel based on the 

current tack direction.

POS

: The vessel's current position.

RACE

: The timer for vessel racing.

REF

: A steer pilot reference.

REL

: Relative to another data field. For example, relative 

humidity.

RUD

: The rudder relative to another data field. For example, 

rudder angle.

SEA

: The temperature of the water.

SOG

: The actual speed of travel, regardless of the course 

steered and temporary variations in heading.

STR

: The steer pilot.

STW

: The speed of the boat relative to the water.

TRP

: A running tally of the distance traveled since the last reset.

TWA

: The angle of the wind relative to the water, referenced 

from the bow of the boat with a port or starboard angle up to 

180 degrees.

TWD

: The true direction of the wind relative to north.

TWS

: The true speed of the wind relative to the vessel.

UTC

: The Coordinated Universal Time.

VMG

: The speed at which you are closing on a destination 

along a route. You must be navigating for this data to 

appear.

WND

: The velocity made good upwind.

XTE

: A cross track error.

Appendix

3