<div><font style="BACKGROUND-COLOR: #33ccff"></font>Hi all,</div>
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<div> Don't have time to go into it all, but this isn't the only GPS protocol, just the only one that is (mostly) standard. Yes it is a bear, but a modicum of perspective here. I had the fun (?) of hacking together a small MNEA ap for a marine GPS unit about a decade or more ago.</div>
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<div>1. It dates back to the days of the dumb terminals and slow RS-232 serial connections, 1980.</div>
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<div>2. At first, it was only intended to allow communication between Loran receivers and autopilots. A short while later, depth finders and some other equipment added to the same serial cable. The 1 second delay was so that these asynchronous "talker" units wouldn't step on each other's sentences and corrupt the data for the "listener" units. A pure hack as a standard, but fast enough and accurate enough is all you need to do is get close enough to a buoy to see it with binoculars.</div>
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<div>3. Having any GPS unit was unheard of until much later, so they were simply added in to the system. At the time they only put you to within 100 meters of the stated position, and boats don't go that fast.</div>
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<div>4. I use to be able to download the specs from the NMEA web site, but I guess they felt that they were loosing control, or needed money, or some BS.</div>
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<div>5. The "standard" includes sentence templates for the manufacturer's even more proprietary sentences. The company that manufactured our unit was open enough to just send me their sentences. The tech support person didn't seem to understand them and was sceptical about anyone working with them. The specs. did let me write code that would report its vendor, model, and firmware version; change the set of sentences it ships per cycle; change the baud rate at which it reports; and change the number of samples it reports per second. There were even proprietary sentences for downloading and uploading waypoints, tracks and doing other things that we were more interested in. This is much more like writing drivers for cards than writing web aps. This is still fairly typical of higher end units.</div>
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<div>6. There are better protocols, but they are even more proprietary and mostly much more expensive. Unless someone starts designing open source circuits to build the hardware, we are stuck with a trade-off. There are cheap hobby units or expensive pro units and even highly accurate specialty units that cost a good annual salary. WOW do they work well! They even get through light tree cover and put you to a centimeter or so without a long occupancy. I am luck enough to get to use them occasionally, but not on my own time.</div>
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<div>After everything else, as talkers to computers or equipment where you don't need built in maps, it is still hard to beat some of the cheaper Garman units. At the more power consuming augmentation settings, 3-4 meters is possible for only $150-$300. There is also a very big helpful hobbyist community to turn to. With other inexpensive units, you are pretty much on your own.</div>
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<div>So right now, if you only need to get within 3 or 4 paces on a tight budget, you pay for it by getting stuck with NMEA-0183 for a couple of hundred bucks or NMEA-2000 more $. To within a foot or so with fast response, proprietary aps and prices in the mid to upper 4 figures. Past that, its into 5 figures.</div>
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<div>However, if your are really rich, you can design an open protocol and a cheap receiver board that uses it. Then give it to the rest of us. I'l be glad to take one, or more. Open source software works out very well But NMEA-0183 and NMEA-2000 are the standards of a HARDWARE manufacturers' association and open hardware protocols and open source hardware designs are always a problem. Again, this is like writing drivers, slow standard hooks, and the fast access protocols belong to the manufacturer and differ widely.<br>
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<div>Enjoy!</div>
<div> Jim</div>
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<div class="gmail_quote">On Mon, Feb 23, 2009 at 8:24 AM, Justin Dearing <span dir="ltr"><<a href="mailto:zippy1981@gmail.com">zippy1981@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">An interesting read from RMSes blog.<br><br>Apologies for the html to the mutt crowd, its what google reader sends out.<br>
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<h3 style="MARGIN: 0px 3px; FONT-FAMILY: sans-serif">Sent to you by Justin Dearing via Google Reader:</h3></div>
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<p><font style="BACKGROUND-COLOR: #ffffff" size="4">Why GPSes suck, and what to do about it</font></p></blockquote>
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<p><span id=""></span>via Armed and Dangerous by esr on 2/23/09</p></blockquote>
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<p><span id=""></span><br> I'm the lead of the GPSD project, a service daemon that monitors GPS receivers on serial or USB ports and provides TPV (time-position-velocity) reports in a simple format on on a well-known Internet port. GPSD makes this job looks easy. But it's not — oh, it's decidedly not — and thereby hangs an entertaining tale of hacker ingenuity versus multiple layers of suck. </p>
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<div><snip></div>
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