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History of GPS by One of its Founders
Old 01-24-2011, 11:59 AM   #1
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History of GPS by One of its Founders

For the Geeks among us (watch for the "Wow!" moments):



TeleNav is a key supplier of mobile phone based navigation and was founded by one of the original engineers on the US GPS satellite system. Bob Rennard is currently their CTO.
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Old 01-24-2011, 12:48 PM   #2
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Great interview. I worked on the predecessor of gps. The transit satellite system, built one of the first civilian decoder hardware. Punched tape programming on a PDP8 with a whopping 2K memory. Far too cumbersome in comparison even of the original gps.

Future use for the augmented system, where is grandpa? Who wondered off, does not know it, and can't find his way back. The cellphone with gps sewn into his underwear will tell when dialed and queried.
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Old 01-24-2011, 01:12 PM   #3
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......
Future use for the augmented system, where is grandpa? Who wondered off, does not know it, and can't find his way back. The cellphone with gps sewn into his underwear will tell when dialed and queried.
I currently have one of these on my dog. I can get her coordinates and nearest cross streets from my cell phone. With a smart phone, I could get a Google map with her location shown. TG I have not needed to use it.
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Old 01-24-2011, 01:14 PM   #4
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I currently have one of these on my dog. I can get her coordinates and nearest cross streets from my cell phone. With a smart phone, I could get a Google map with her location shown.
Once you can get her trained to "bomb" on target you'll really have something!
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Old 01-24-2011, 02:07 PM   #5
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Old 01-24-2011, 09:41 PM   #6
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Great interview. I worked on the predecessor of gps. The transit satellite system, built one of the first civilian decoder hardware. Punched tape programming on a PDP8 with a whopping 2K memory. Far too cumbersome in comparison even of the original gps.
We pretty much lived and died by that system in the 1980s submarine force... rockin' & rollin' at periscope depth for all the time necessary for the navigation electronics tech to lock into the signal and track it through its Doppler shift.

Woe betide the OOD who got the radio mast out of the water (high out of the water, and preferably bone dry to boot) a few seconds too late and was directed to wait for the next pass.

A few years later on a 1990s submarine navigation system, I was getting GPS fixes before I even got the scope out of the water.
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Old 01-25-2011, 10:57 AM   #7
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For those with a penchant for mental self flagellation a brief description of the Transit satellite system is at the following link:

Transit
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Old 01-25-2011, 11:55 AM   #8
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We pretty much lived and died by that system in the 1980s submarine force... rockin' & rollin' at periscope depth for all the time necessary for the navigation electronics tech to lock into the signal and track it through its Doppler shift.

Woe betide the OOD who got the radio mast out of the water (high out of the water, and preferably bone dry to boot) a few seconds too late and was directed to wait for the next pass.

A few years later on a 1990s submarine navigation system, I was getting GPS fixes before I even got the scope out of the water.
Why would nuclear subs have GPS, I thought the idea was NOT to be found or located??
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Old 01-25-2011, 11:58 AM   #9
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Why would nuclear subs have GPS, I thought the idea was NOT to be found or located??
That always works for me: The best way to not be found or located is to get lost.
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Old 01-25-2011, 01:26 PM   #10
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Nords would be better to answer but you have to know where you are exactly to program a missle flight as I understand it.
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Old 01-26-2011, 12:25 AM   #11
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Nords would be better to answer but you have to know where you are exactly to program a missle flight as I understand it.
IIRC (and I'm reaching way into the memory deep freeze here), a transit pass (as it was called over two decades ago) would let you fix your position to within a half mile. A GPS fix (of at least three satellites) would let you fix your position to a quarter-mile.

We used to joke that a fourth GPS satellite would also tell you how much antenna you had sticking out of the water.

Once you had that fix plotted on the chart (yeah, I know kiddies, we dinosaurs used paper charts back in them days) then you'd go deep and use your onboard inertial-navigation system to dead-reckon your movement. It was pretty accurate for 12-24 hours but depending on how fast you raced around you had to assume that it was degrading in accuracy by roughly a tenth of a mile every hour. On an attack submarine you'd be at PD twice a day (at least, hopefully several times a watch) and you'd pick up a fix as part of that routine so you were usually pretty close. On a 1980s boomer you'd come up once a month or so, but I'll get back to that in a few paragraphs.

So however you got it, once that fix was in the system you'd drive around underwater while the SINS (and the quartermaster) would dead-reckon your position. That position would start with an uncertainty circle around it of a quarter-mile (or half-mile) radius and would eventually grow to several miles. This was no problem in the middle of the Pacific Ocean but it could get a little hair-raising in certain areas near certain land masses with much shallower "charted" soundings where you would rather not be even going active on the fathometer, let alone waving your antenna around.

At some point you had to decide whether you'd rather run aground or risk the antenna exposure for a satellite fix. The transit pass would take agonizing minutes using a huge antenna (big radar cross-section) with much watchstander bickering and finger-pointing. The GPS fix (from a tiny receiver on top of the periscope) would be onboard before I'd even gotten enough scope high enough out of the water to make a safety sweep. Once or twice we'd get lucky a fix before I even had the scope out of the water.

It wasn't considered essential to have a tight GPS fix for a TOMAHAWK missile launch, but it sure helped you push the limits of the max-fuel range. Once the TLAM hit its initial waypoint enroute the target, it started getting its own fixes-- either from land contours or from GPS satellites. Those missiles have gotten way smarter over the years by at least two generations of technology from the ones I used, so that last sentence may no longer be relevant.

Ballistic missiles were another concern but the solution was to use bigger warheads and shorter ranges until the nav tech caught up. The early POLARIS model was named for its technology allowing it to get a celestial fix enroute the target. I don't remember how POSEIDONs fixed their position but we had a lot more fuel & warhead to work with and we stayed in the North Atlantic most of the time. The TRIDENT missiles use a much-more-accurate ring-laser inertial navigator, but a submarine position fix before launch could give it that much more fuel margin to guarantee a solid hit inside the error circle.

The real limiting factor on coming to PD wasn't navigation but communications. Back in the 1980s and early '90s (the "good ol' days") a hotshot UHF satellite transceiver could send/receive at 2400 bits per second. (Not bytes!) Using one of those with an antenna mast you'd come up to PD at least twice a day to pick up radio traffic so that the shore comms center could load you up with more, and radio traffic was the high point of the day because if you got ahead of the official traffic then the shore comms guys might slip in a few sports scores & familygrams.

Boomers could also stream a buoyant VLF communications wire (several thousand feet long) and a buoy with its own little HF wire. Then you'd poke around at 3-4 knots and 400 feet of depth, holding your breath and not making any sudden moves, while your radio techs would try to coax a decent signal out of the wires floating behind you on the surface. (You'd keep this up for 70 or 80 days, 24/7.) You don't get much of a bit rate at VLF frequencies but you could clear that same broadcast in an hour or two instead of a few seconds. That meant you didn't need to come up to PD, so you didn't. Boomer crews didn't get much practice at coming to PD so they sucked at it and didn't really want to do it anyway.

Luckily boomers are also able to use a couple of alternate methods to fix their position while submerged. I'm not sure whether or not those are still classified, but when you're poking around the ocean at 3-4 knots then one of those fixes will be "good enough" for a few weeks.
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Old 01-26-2011, 04:56 AM   #12
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Thanks for the post! GPS is the only part of my work - surveying, mapping, and asset inventories (nothing as exciting as nuclear subs) that carried into my personal life. I used to carry a handheld GPS while biking/hiking. Now its all on my cell phone.

I'm like Travelover's dog - DW sends a text asking where I am and I respond with:

I am here | free Mobile GPS Tracking Service
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