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'[OT] UT-41 USB GPS receiver'
2010\11\08@014710 by Joshua Shriver

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I bought this years ago and never had any luck. Dug it up today and
tried it out and finally able to poll it for GPS nmea data. However
the gps location it gives when put in google earth is somewhere in
mainland china. Anyone come across something like this? I'm not
entirely sure it's actually getting a signal or a lock even though
it's supposed to have 12 channels. Receiving is at least partially
working because I am getting a correct time.

OT for my own post :) I bought this just to learn more about GPS's
back before they were reasonably cheap. Does anyone recommend a nice
serial based GPS module that could be used in projects?  I'm working
with PIC and the MSP-EXP430 board.


-Jos

2010\11\08@021225 by Richard Prosser

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Josh,

It sounds like the unit is returning its last valid position. How long
did you leave it running for? It can take 15mins to obtain an almanac
and it could be a little "confused". Older units also can take a while
to get things sorted out & perform the calculations etc. The time is
transmitted as GMT so doesn't require the location to be calculated.
In fact I think you only need one satellite for time.

If you haven't already, I'd let it run for an hoyr or so in a good
location and see what happens then.

Re the serial module I can't be of much help although I'd be
interested in what you decide on & how it works out.


Richard

On 8 November 2010 18:47, Joshua Shriver <spam_OUTjshriverTakeThisOuTspamgmail.com> wrote:
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>

2010\11\08@021547 by Joe McCauley

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How long did you leave it running for? A GPS can take quite a bit of time to give a sensible output if moved a long distance while powered off (which happened in your case).

Assuming you have an antenna (many OEM modules don't), leave it running with a clear view of the sky for an hour or so. I'd be surprised if you don't get a valid fix.

Joe

________________________________________
From: .....piclist-bouncesKILLspamspam@spam@mit.edu [piclist-bouncesspamKILLspammit.edu] On Behalf Of Joshua Shriver [.....jshriverKILLspamspam.....gmail.com]
Sent: 08 November 2010 06:47
To: Microcontroller discussion list - Public.
Subject: [OT] UT-41 USB GPS receiver

I bought this years ago and never had any luck. Dug it up today and
tried it out and finally able to poll it for GPS nmea data. However
the gps location it gives when put in google earth is somewhere in
mainland china. Anyone come across something like this? I'm not
entirely sure it's actually getting a signal or a lock even though
it's supposed to have 12 channels. Receiving is at least partially
working because I am getting a correct time.

OT for my own post :) I bought this just to learn more about GPS's
back before they were reasonably cheap. Does anyone recommend a nice
serial based GPS module that could be used in projects?  I'm working
with PIC and the MSP-EXP430 board.


-Jos

2010\11\08@083807 by Matt Bennett

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On Mon, November 8, 2010 12:47 am, Joshua Shriver wrote:
> OT for my own post :) I bought this just to learn more about GPS's
> back before they were reasonably cheap. Does anyone recommend a nice
> serial based GPS module that could be used in projects?  I'm working
> with PIC and the MSP-EXP430 board.

Sparkfun has a bunch of decent serial GPS modules.  Almost everything you
will find will put out a NMEA 0183 sentence, which are pretty well
documented in multiple places on the net. Sticking with NMEA sentences is
the best bet, as you can have good portability between receivers. If you
want to go into greater depth (pseudo-ranges, for example, which are used
in differential GPS)... if you find anything, I'd like to know. Pseudo-range output is not part of the NMEA standard and does not appear
to be a priority among module makers, and only appears to be a well
documented feature on high end surveying GPS devices.


The views I express are my own, not that of my employer, a large
multinational corporation that you are familiar with

2010\11\08@084924 by Carl Denk

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Some of the GPS's require input of present position (roughly), and time to establish a position. I never understood this, since the time is broadcast frequently, and the data needed to calculate a position. But the current ephemeris (satellite position  and position corrections) needs to be received and processed by the receiver before a position can be established.

Also there are periods at locations where GPS is not available due a satellite being down, possibly due to a repositioning action, a blackout of an area, or other interference. Many time this is published. One source is FAA notams (Notice to Airmen) that include airport and radio navigation equipment conditions.

If you have access to another GPS unit, check if it works near the questionable unit.

For a new unit you might consider a handheld like used for hiking/boating. Many of them have RS-232 in some standard format outputs. These are very handy, not like a dedicated driving GPS. I have a Lowrance I-finder C (color). With the data base loaded it has both barometric and GPS altitude, topo contour lines, creeks, small roads, and can take you to a street address. We use it for driving by entering the route ahead of time, and then as estimated time enroute and arrival, plus actual instantaneous speed to 1/10 MPH. We also use it for hiking to know where the vehicle is.

On 11/8/2010 1:47 AM, Joshua Shriver wrote:
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>

2010\11\08@100125 by John Ferrell

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A long while back a friend of mine bought a unit to interface to an airborne ( model airplane) experiment and it took over 24 hours to find itself!

I have heard there are GPS modules available for about $50 for amateur radio APRS use. Try searching ham aprs gps?

John Ferrell W8CCW

"The same prudence which in private life would forbid our paying our own money for unexplained projects, forbids it in the dispensation of the public moneys." --Thomas Jefferson


On 11/8/2010 1:47 AM, Joshua Shriver wrote:
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> -Jos

2010\11\08@102457 by Marcel Duchamp

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My 2 cents:

Throw it away unless you love a challenge of spending countless hours waiting for a fix that never comes or is subject to enormous variation of location data.

Gps technology has come leaps and bounds since "years ago".  I have a ublox LEA 5H that rarely takes over a minute to get a fix from a cold start..

Need help deciding which one? Sparkfun has a great tutorial on the subject.  See it here:

http://www.sparkfun.com/commerce/tutorial_info.php?tutorials_id=127



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>> -Josh

2010\11\08@103000 by Marcel Duchamp

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One more resource from Sparkfun:

http://www.sparkfun.com/commerce/tutorial_info.php?tutorials_id=169

This is a comparison of tracking abilities of various modules.

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>> -Josh

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