Morgan

Does anyone know of a GPS unit that will work with a laptop that outputs live positional information (lat/long) into a file that one can work with??? Please help!

dav

I would expect all of the marine and aviation units to do that. They are used to talking to external equipment.

Consumer handheld GPS units do it on demand, but I would not expect any of them to provide streaming data.

I do not know any specific units to recommend, sorry.

Max

Yes, lookup "NMEA output" it's exactly what you're after.

Most units have this as an option.

ninja279

I use photo tagging software with my Ipaq 5915 (PDA GPS) it gives lat, long, height, slope and GPS real time stored at time intervals of my choosing.
I can then upload information into Google earth.

gpsnetwerx

max, i just got a nuvi 260w to test with an odometer based measurement instrument for highway inventory. i deal with dual freq gps on a high level and have dabbled with the navigation grade gps for a while.

i cannot find the settings on the nuvi that will allow me to poll the nmea. i assume the nmea is a standard gga message like the 76s, but be damned if i can find it on the nuvi. garmin tech support was useless.

any ideas?

cheers
scott

Max

hey Scott, sorry - I don't think the Nuvi is happy doing nmea out. I've tried it with Garmin mapping products in dynamic mode and it just sits there.

But...it is a good thing to add to my bucket list

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bjthom

I'm also interested in a GPS device with NMEA output. The reason for this is that I need accurate timestamps. GPS satellites' standardized time is exactly what I need for a project of mine. That said, does anyone have any advice on a basic gps unit that can handle this sort of thing? Furthermore, when parsing the NMEA output, does anyone know how many digits are shown? For example does it show anything beyond the standard hh:mm:ss and into fractions of seconds? Thanks.

dav

bjthom, wouldn't the atomic clock signal be easier to access?

Using a GPS for "not intended use" seems like the long way around the block...

Max

Hey BJ, what sort of project if you don't mind me asking?

(welcome to the site btw .)

The Garmin handheld 60series offers a serial out, but you can probably get straight NMEA out from any of the lesser expensive usb 'puck style' antenna's. I know the Microsoft Streets and Trips typically uses a Pharos unit (varies by year) but that is essentially a USB-to-serial device with a NMEA gps on the other end. I have the 2007 S&T and have used this for NMEA in on a couple different applications.

I guess the question is are you trying to use a GPS with nmea out, or a laptop/other perihpheral that is a data terminal and needs a sensor in?



To backtrack a bit...the timing signals you'd be pulling out of the nmea would be off by a short amount of time. What accuracy time are you requiring? S1? S3?

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Max

Thats what you'd think right? but GPS is viewed as S0 source...

Here is some more info:
Using a Garmin GPS 18 LVC as NTP stratum-0 on Linux 2.6

Better yet:
USNO NETWORK TIME SERVERS



This might be cheaper, as a DIY project of course
NIST-F1 - Cesium Fountain Atomic Clock

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dav

Max, I was just assuming that with the small processor in handheld GPS units, and the fact that they use a serial connection, that by the time the signal is received, processed and transferred to another device that milliseconds will have elapsed.

Whereas if you have a time server that is intended for that function, it will not delay the signal like a consumer grade handheld GPS unit might.

That's all. I didn't intend to slight the time signal from GPS.

Max

Oh, in that case you'd be absolutely correct
The device you're syncing to has to understand that the source is offset by N msec or you're as good as nothing

However, the timing will be consistent...so the drift characteristics will still be static I guess

gpsnetwerx needs to chime in here....

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Max

It's ok, you can talk bad about it here, we won't tell your Nuvi

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Max

are you asking me , or bj about his project?

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gpsnetwerx

timing depends on the project. on our reference stations we have the ability to obtain the timing from a port on the sensor (PPS). it sends 1 "pulse per second" to what ever device or application that requires a timing pulse. the timing is extremely accurate.

as far as a garrmin is concerned, getting a time stamp is not difficult via NMEA. it seems that max and crew have the right approach. typically the timing on a consumer grade gps is .1 mili sec over short term.