Length of NMEA transmission intervals / measuring rates?

[Falkensegler]

Hello,
I would like to know what typical time intervals between two consecutive NMEA sentences are.

For GPS, there are typically 1-2 measurements per second, and several NMEA sentences for each.
But for other devices, the manuals do not say anything about measuring rates.

So, does anybody know, what typical measuring rates / transmission intervals of
-depth sensor
-wind sensor
-speed sensor
-...
are?

[Paul Elliott]

With NMEA-0183 gear it's typically one measurement per second. Some compasses, especially rate-compensated or "gyro" types will send outputs more often, but for this faster reporting rate they may require an NMEA interface speed of 38400 bps rather than the standard 4800 bps.

I don't have reporting rate information for NMEA-2000 interfaces, but it's probably similar.

[smac999]

hook them up to a serial port and run HyperTerminal. you'll see all the data real time. and can see / measure whatever you want.

[GordMay]

Greetings and welcome aboard the CF, Falkensegler.

Does this help?

3.1 "Simple" data format
The simple format consists of a single data byte transmitted at
intervals of 0.8 to 5 seconds ...

3.2 "Complex" data format
The complex format consists of a data block of 37 bytes of
(mostly) readable ASCII text giving cross-track error, bearing
to waypoint, present Lat/Long, and a binary status byte. The
data block shall be sent at intervals of 2 to 8 seconds ...

From ➥ http://www.kh-gps.de/nmea.faq

[reed1v]

Great answer. To the point.

[tanglewood]

Things I know that are faster than once per second are:

- Heading, sometimes know as Fast Heading, can be 10hz or even 20hz. Most autopilots want 10hz or faster heading.

- Position, rapid update. GPS position info at 10 hz

- Rudder position. Typically 10hz

- I'm pretty sure I've seen weather info come at 10hz, but am not certain.

There probably are more, but that's what I can thing of now.

[Emouchet]

On my Raymarine ST50 Multi, the NMEA output is every 2 seconds for wind speed and direction, depth and water temp.

Speed is every second.

[Falkensegler]

The NMEA 0183 specification states that between two sentences of the same type there should be a 0.8 - 5 second time interval. Of course, if a device transmits sentences of different types, the delay between two consecutive sentences can be shorter.

[Emouchet]

Modern GPS devices have now an output rate of 10 position fix per second.

More advance positioning devices that combine GPS, GLONASS and inertial computing are even faster, up to 50 position fix per second.

They still use NMEA ascii string output, but as stated, using a faster baud rate, such as 38400 or even higher, up to 115200 bds.

Probably not really useful for boater though moving 5-10 knots.

[Davidasailor]

Navico's GoFree system provides NMEA data over wifi. They show the data rates for each NMEA sentence at http://www.bandg.com/documents/produ...epslanguage=it. For the most part refreshes are 1 per second.


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