Has anyone developed NMEA type strings for other science data?

From: Dwight Arrants [dwight.arrants@duke.edu]

Sent: Friday, March 30, 2001 5:42 PM

To: RVTEC

Subject: NMEA and sci data

Hi All,

I am working on a system to provide NMEA data to science parties on the R/V
Cape Hatteras. I would like to make all of the underway data available in
real time, not just GPS data. NMEA handles a few things like wind speed and
direction, water temp etc. but the standard does not address any scientific
instruments salinity, PAR etc.

Is there any standard for transmitting this type of data?

Is anyone else interested in transmitting this type of data?

Should we develop a standard (with or without NMEA)?

Thanks
Dwight Arrants

Dwight Arrants
R/V Cape Hatteras
DSO / Marine Technician
email : dwight.arrants@duke.edu
phone : (252)504-7587
fax : (252)504-7651

Answers:

From: Barrie Walden [bwalden@whoi.edu]

Sent: Monday, April 02, 2001 10:15 AM

To: Dwight Arrants

CC: RVTEC

Subject: Re: NMEA and sci data

Dwight,

I am not aware of a standard used for transmitting all of the available
underway data. As you said, standard NMEA sentences do not cover the
ground but the basic format is well thought out and can be applied to
many data items provided you are planning on placing a computer in the
middle of the transmission process. The alternative is to route the
sensor output directly and eliminate concerns about your computer's
performance but then you're stuck with the existing data
format. One thing to consider - if you are interjecting your computer
into the data distribution process then you probably need to consider
data time stamping and this is not an NMEA format strong point.

No matter which route you chose you will need to provide the science
parties with the format definitions. You can either describe the
sensor's output as defined by the vendor or describe the format you have
devised.

On WHOI ships we are distributing NMEA position and heading information
directly from the sensors. The ship data loggers can distribute any
other available data in just about any reasonable format but we rarely
get requests for this. It seems that most scientists simply want an
ASCII file at the end of the day, preferably something which can be
easily imported into Excel.

Barrie
WHOI

From: Marc Willis [willis@oce.orst.edu]

Sent: Monday, April 02, 2001 10:36 AM

To: Dwight Arrants

Cc: rvtec@diu.cms.udel.edu

Subject: Re: NMEA and sci data

Dwight,
We have been using NMEA as a data exchange format on WECOMA for
several years. Since many of the sensors we use do not have standard NMEA
sentences, we have devised an implementation of the NMEA "Proprietary"
scheme. Basically, the sentence starts with $P and whatever you like as a
descriptor. You see this with some equipment (e.g. the Ashtech 3DF,
$PASHR,ATT sentence). Many of the manufacturers of oceanographic equipment
have signed on to NMEA, and have their own identifiers. You can make up
your own, as long as it starts with $P and conforms to the NMEA standard
for sentence structure. I'd be happy to share what we've done, if you're

Marc

From: Marc Willis [willis@oce.orst.edu]

Sent: Monday, April 02, 2001 11:34 AM

To: rvtec@diu.cms.udel.edu

Subject: WECOMA underway data record - NMEA

RVTEC'ers,
In response to John's suggestion, here is a typical WECOMA data
record in NMEA format. This is from the info given to scientists along
with the data files. This format is usually NOT used by the scientists, as
we have utilities to extract the data in real time and provide them with
"cooked" files of real values (not just voltages) in a comma-separated
format (ideal for Excel). We have chosen to use the $PXXX leader to
identify the "method" of measurement (voltage, frequency, whatever),
followed by a second identifier which gives the type (temperature,
conductivity, wind) and location of the measurement (flow-thru in lab,
engineroom, doghouse, etc), and which sensor is in use. It's not perfect,
but it works for us. If you're doing something better, let's hear about
it. No fair lobbing grenades unless you post your scheme too!


Marc

*****************************************************

WECOMA Data Acquisiton Record Explanation

$PSTA,2
$ZAZDA,081:23:14:06
$PASHR,ATT,170013.0,115.01,-000.05,+000.13,0.0026,0.0212,0*2D
$GPGGA,231312.257,4437.5449,N,12402.7015,W,3,08,1.0,010.1,M,021.8,M,,*70
$GPVTG,033.8,T,015.5,M,000.0,N,000.0,K*47
$PKEL99,22031999,231455.972,HF,19.61,1,LF,00.00,0,44 37.542697N,1242.698495W
$WIXDR,1010.55
$PVOLT,WSD001,702.2400,283.3600,465.2091,140,5.7034
$PVOLT,AOD001,3549.2800,3539.0400,3545.6309,140,10.1829
$PVOLT,AYD001,561.2800,560.0000,560.7863,140,10.3520
$PVOLT,HYD001,802.1600,798.7200,800.3937,140,80.0394
$PVOLT,DSD001,581.2800,566.8800,574.3737,140,1823.4086
$PVOLT,DPD001,0.4800,0.0000,0.0114,140,1213224143160.4487
$PVOLT,DLD001,0.6400,0.0000,0.1097,140,5.4857
$PVOLT,LCD001,3478.0800,3477.1200,3477.5863,140,9.3176
$PVOLT,LHD001,3492.6400,3488.9600,3490.7760,140,9.4627
$PVOLT,HEA001,0.4800,-0.1600,0.0731,140,179.9974
$PVOLT,WHS001,1.2308,0.7148,0.9390,140,-112.0000
$PVOLT,WSS001,1001.4400,496.4800,0.6979,140,13.9767
$PFREQ,TSF001,8889.6000,8887.5200,8888.8937,140,16.9589
$PFREQ,CSF001,2687.7600,2687.7600,2687.7600,140,0.0185
$PUNIT,SAF001,140,0.1057
$PFREQ,TSE001,7315.5200,7305.7600,7312.4046,140,10.3222
$PVOLT,FVB001,0.6400,-0.1600,0.1131,140,0.0000
$PVOLT,WHP001,3.3775,0.2847,0.9730,140,-110.0000
$PVOLT,WSP001,1047.8400,490.0800,0.7262,140,14.5408
$VDVBW,-00.05,00.08,V,-00.05,00.08,A*1
$PEND,2

The following is an explanation of the DAS, data acquisition system,
record format. The above is an excerpt from a trial run of the
DAS. The example file used is 032215.txt, indicating the file was
started on March 22 at 3:00pm. Each file contains an hour of data,
records being made each minute. See the proceeding page, which
indicates the line numbers used as a reference in the following
record structure explanation.

Line

1	Start of record and record number
2	True Time output string in the format DDD:HH:MM:SS
3	Ashtech GPS output string in NMEA format
4,5	P-Code GPS output string in NMEA format
6	Knudsen Echosounder output string, $PKEL99 Knudsen proprietary address, Date, Time hhmmss, HF, high frequency depth to surface, HF valid flag 1= valid,LF, low freqency to surface, LF valid flag, position (latitude and longitude)
7	Barometer output string in millibars
8-19	$PVOLT is a proprietary address indicating the input is a voltage, the code for the Meteorological instruments (see the WECOMA Meteorological Suite for code explanation), maximum sample value during a minute record, minimum and mean value for same period, number of loops (samples) made during that period, and the calculated engineering units using the mean value
17	Note this is the Gyro output which at this time is not operational
20-21	$PFREQ is a proprietary address indicating the input is a frequency, from the Sea-Bird Electronics sensors, for the Flo-Thru system. The values again are maximum, minimum, mean, number of loops, engineering units (see the M1000 Module DAQ Addressing).
22	$PUNIT is a proprietary address indicating the output is in dimensionless unit, SAF001 is the calculated salinity for the Flo-Thru system using the mean values (see lines 20 and 21)
23	$PFREQ is a proprietary address indicating the input is a frequency, from the Sea-Bird Electronics sensor, for the Sea Surface Temperature. The values again are maximum, minimum, mean, number of loops, engineering units (see the M1000 Module DAQ Addressing).
24	$PVOLT is a proprietary address indicating the input is a voltage, from the underway fluorometer. The values again are maximum, minimum, mean, number of loops, engineering units (see the M1000 Module DAQ Addressing).
25-26	$PVOLT is a proprietary address indicating the input is a voltage, the code for the Meteorological instruments (see the WECOMA Meteorological Suite for code explanation). The values again are maximum, minimum, mean, number of loops, engineering units (see the M1000 Module DAQ Addressing).
27	Speed Log output string in NMEA format.
28	End of record and record number.

A .pdf file of above information

A .pdf file of Wecoma MET Suite with calibration
coefficients and instrument identifiers.

Marc Willis Oceanic and Atmospheric Sciences
willis@oce.orst.edu Oregon State University
Ph: 541/737-4622 104 Ocean Admin. Building
Fax: 541/737-2470 Corvallis, OR 97331-5503 USA