Airmar PB100 WeatherStation User manual

AIRMAR®PB100 WeatherStation™ Technical Manual revision 1.009
PB100 WeatherStation™
Technical Manual
also covers model LB100
Revision 1.009
AIRMAR Technology Corporation
35 Meadowbrook Drive
Milford, NH 03055-4613
[phone]

AIRMAR®PB100 WeatherStation™ Technical Manual revision 1.009
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1. Introduction
This document is a supplement to the Airmar PB100 WeatherStation™ Owner's Guide.
This document provides a detailed description of the communications protocol for both
transmitted and received NMEA 0183 sentences used by the PB100 WeatherStation
instrument.
At this writing there are three models of the WeatherStation instrument: the WAAS1
capable PB100 and LB100, and the non-WAAS capable PB100. This document covers
all models.
For further information about the NMEA 0183 protocol, refer to the document, NMEA
0183 Standard for Interfacing Marine Electronic Devices, v3.01, available from the
National Marine Electronics Association (www.nmea.org).
2. NMEA 0183 Interfaces
The Airmar WeatherStation instrument has a single standard NMEA 0183-compliant
output channel, and a single standard NMEA 0183-compliant input channel. The unit
transmits standard NMEA 0183 sentences on its output channel. It also recognizes
standard and proprietary NMEA 0183 sentences received on its input channel. The
standard baud rate for both input and output channels is 4800 baud, though if desired this
may be increased to 38400 baud via a proprietary command.2
The transmitted NMEA 0183 sentences are described in section 2.1. Received NMEA
0183 sentences and proprietary commands are described in section 2.2.
2.1. Transmitted NMEA 0183 Sentences
By default, only certain NMEA sentences are enabled for transmission. Other sentences
may be enabled individually for transmission via commands sent to the input channel.3
The standard transmission interval for most of the transmitted sentences is once per
second. However, in models that include an integrated GPS, if every sentence were
enabled for transmission, there would not be enough bandwidth in the output channel at
1WAAS - Wide Area Augmentation System, an advanced feature of some GPS receivers.
2See the $PAMTC,BAUD command.
3See the $PAMTC,EN command.

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4800 baud to output all sentences within a one second timeframe. Therefore, one or more
of the following remedies should be employed:
•To conserve bandwidth, only enable for transmission those sentences required for
the given application, and disable all others.
•Reduce the frequency of transmission for less critical sentences.
•Increase the overall bandwidth eightfold by increasing the baud rate from the
standard 4800 baud to 38400 baud (though keep in mind that most NMEA 0183
instruments are not capable of operating at 38400 baud)
All NMEA sentences transmitted by the WeatherStation instrument include a checksum
at the end of the sentence, consisting of an asterisk (*) followed by two ASCII
hexadecimal characters. In the detailed specifications to follow, these hexadecimal
characters are designated by “hh”.
The standard NMEA 0183 sentences provided by the WeatherStation instrument are
summarized in Table 1. Each of the transmitted sentences in Table 1 is described in
detail on the subsequent pages.
The Maximum Length (chars) column in the table indicates an expected worst-case
scenario that can be used for bandwidth budgeting. The total time in seconds required to
transmit all enabled sentences in a single interval is
ratebaud charactersofnumberTotal
timeontransmissiTotal _10___ __
×
=

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Table 1: NMEA 0183 Regularly Transmitted Sentences1
Sentence Description PB100 LB100 Enabled
by Default Maximum
Length
(chars)
$GPGGA GPS Fix Data 33382
$GPGLL Geographic Position – Latitude/Longitude 33No 48
$GPGSA GNSS DOP and Active Satellites 33No 66
$GPGSV GNSS Satellites in View 33No 70
$HCHDG Heading, Deviation and Variation 33No 33
$WIMDA Meteorological Composite.
Barometric pressure, air temperature,
relative humidity, dew point, wind direction,
wind speed
33381
$WIMWD Wind Direction and Speed, with respect to
north
3232341
$WIMWV
(relative) Wind Speed and Angle, in relation to the vessel’s bow/centerline (relative)
33328
$WIMWV
(theoretical) Wind Speed and Angle, in relation to the vessel’s bow/centerline (theoretical)
3232328
$GPRMC Recommended Minimum Specific GNSS
Data
33No 74
$GPVTG Course Over Ground and Ground Speed 33342
$WIVWR Relative Wind Speed and Angle 33No 41
$WIVWT True Wind Speed and Angle 333341
$WIXDR Transducer Measurements: wind chill and
vessel attitude
33No 73
$YXXDR
(type A) Transducer Measurements: wind chill, heat index, and station pressure
33No 74
$YXXDR
(type B) Transducer Measurements: vessel attitude (pitch and roll)
33No 43
$GPZDA Time and Date 33338
1As of firmware version 2.000/2.000.
2True wind data is provided in the $WIMWD and $WIMWV (theoretical) sentences if SOG/COG,
heading, and magnetic variation data are available from an internal or external GPS and compass.
3$WIVWT True Wind Speed and Angle referenced to water is provided only if water referenced speed is
available via the NMEA 0183 input from an Airmar® Smart™ speed sensor.

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NMEA 0183 TRANSMITTED SENTENCE
$GPGGA
Summary
NMEA 0183 standard GPS Fix Data.
Syntax
$GPGGA,<1>,<2>,<3>,<4>,<5>,<6>,<7>,<8>,
<9>,<10>,<11>,<12>,<13>,<14>*hh<CR><LF>
Fields <1> UTC of position, in the form hhmmss
<2> Latitude, to the nearest .0001 minute
<3> N if field <2> is North Latitude
S if field <2> is South Latitude
<4> Longitude, to the nearest .0001 minute
<5> E if field <4> is East Longitude
W if field <4> is West Longitude
<6> GPS quality indicator:
0 = Fix not available or invalid
1 = GPS SPS Mode, fix valid
2 = Differential GPS, SPS Mode, fix valid
3 = GPS PPS Mode, fix valid
4 = Real Time Kinematic (RTK)
5 = Float RTK
6 = Estimated (dead reckoning) Mode
7 = Manual Input Mode
8 = Simulator Mode
When providing data from the WeatherStation instrument’s internal
GPS, the only valid values for the GPS quality indicator are 0, 1, and 2
(if WAAS enabled).
<7> Number of satellites in use, 0-12
<8> Horizontal dilution of precision (HDOP)
<9> Altitude relative to mean-sea-level (geoid), meters (to the nearest
whole meter)
<10> M

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<11> Geoidal separation, meters (to the nearest whole meter). This field is
not provided by the WeatherStation instrument, and appears as a null
field.
<12> M. This field is not provided by the WeatherStation instrument, and
appears as a null field.
<13> Age of Differential GPS data, seconds. This field is not provided by the
WeatherStation instrument, and appears as a null field.
<14> Differential reference station ID, 0000-1023. This field is not provided
by the WeatherStation instrument, and appears as a null field.
Default State
Enabled. Transmitted once per second.
Notes This sentence may be enabled or disabled via the $PAMTC,EN,GGA command.
However, if the WeatherStation instrument receives a VTG or RMC sentence
from an external GPS, then this sentence shall not be transmitted.

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NMEA 0183 TRANSMITTED SENTENCE
$WIMDA
Summary
NMEA 0183 standard Meteorological Composite.
Syntax
$WIMDA,<1>,<2>,<3>,<4>,<5>,<6>,<7>,<8>,<9>,<10>,<11>,
<12>,<13>,<14>,<15>,<16>,<17>,<18>,<19>,<20>*hh
<CR><LF>
Fields <1> Barometric pressure, inches of mercury, to the nearest 0.01 inch
<2> I = inches of mercury
<3> Barometric pressure, bars, to the nearest .001 bar
<4> B = bars
<5> Air temperature, degrees C, to the nearest 0.1 degree C
<6> C = degrees C
<7> Water temperature, degrees C (this field left blank by WeatherStation
instrument)
<8> C = degrees C (this field left blank by WeatherStation instrument)
<9> Relative humidity, percent, to the nearest 0.1 percent
<10> Absolute humidity, percent (this field left blank by WeatherStation
instrument)
<11> Dew point, degrees C, to the nearest 0.1 degree C
<12> C = degrees C
<13> Wind direction, degrees True, to the nearest 0.1 degree
<14> T = true
<15> Wind direction, degrees Magnetic, to the nearest 0.1 degree
<16> M = magnetic
<17> Wind speed, knots, to the nearest 0.1 knot
<18> N = knots
<19> Wind speed, meters per second, to the nearest 0.1 m/s
<20> M = meters per second

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Default State
Enabled. Transmitted once per second.
Notes This sentence may be enabled or disabled via the $PAMTC,EN,MDA command.
The barometric pressure provided in this sentence is the altimeter setting, which is
the barometric pressure corrected for altitude above sea level. See the transmitted
$YXXDR(A) sentence, and the received $PAMTC,ALT command, for further
information.

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NMEA 0183 TRANSMITTED SENTENCE
$GPZDA
Summary
NMEA 0183 standard Time and Date
Syntax
$GPZDA,<1>,<2>,<3>,<4>,<5>,<6>*hh<CR><LF>
Fields <1> UTC of position, in the form hhmmss
<2> Day, 01 to 31
<3> Month, 01 to 12
<4> Year, four digits (e.g. 2006)
<5> Local zone hours, always set to 00 in PB100
<6> Local zone minutes, always set to 00 in PB100
Default State
Enabled. Transmitted once per second.
Notes This sentence may be enabled or disabled via the $PAMTC,EN,ZDA command.
However, if the WeatherStation instrument receives a VTG or RMC sentence
from an external GPS, then this sentence shall not be transmitted.