Infiltration

Finn location: Plano, TX Gender: Male \|	GPS Device for Draining < on 6/29/2005 6:48 AM >

	I've been exploring for 4 or 5 months now, and the question has long been asked by me and my crew, "Is there a GPS that can work 50 feet below ground?" Cell phones never work unless you just want to use them to see what time it is, and I'm pretty sure nearly all of them need a line of sight to the sky to work. The best we could come up with is pinpointing where we start and pinpoint the end. The only problem with that idea is that when you're draining, you rearly come to "an end", usually the tunnels get too small and you turn back. I don't really want a GPS so I can tell where I am, or I'm afraid I'll get lost. Mostly I'd just like to see how for I've gone and what I'm under at that precise moment. (As I'm sure some of you know, there are few things in life quite like going somewhere and saying, "I've been under here." I do it at the Mall all the time.) So, if anyone's found anything useful, please let me know. Rest in Peace, Ninjalicious. I know that wherever you are, you're finding the best sites for us already.

duck219 \|	Re: GPS Device for Draining <Reply # 1 on 6/29/2005 1:46 PM >

	I am a student here at Ohio University, and there are a lot of interesting GPS technologies being developed here, but they are a long way off right now from the marketplace. Most notably, GPS technology for mining is being developed so that you can calculate you position miles back into a mine! Also, there is development of using cellphone antennas and tv satellites to navigate off of as well... Us ue'rs are just too far ahead of our time!!!

MacGyver location: St Paul, Minnesota Gender: Male "Someone go find me a paperclip, a D-cell battery, and a cheese grater" \|	Re: GPS Device for Draining <Reply # 2 on 6/29/2005 6:22 PM >

	It is currently not possible to use any kind of consumer GPS beneath anything. GPS works by timing signals from multiple satellites in orbit around the earth. The radio transmitters on these satellites only produce something like 5 or 10 watts, which is very little power considering typical FM radio broadcast stations transmit with power outputs in the neighborhood of 50,000 watts, and it is difficult or impossible to receive even a local FM broadcast inside of a shallow freeway tunnel. Generally speaking, if you don't have a clear view of the sky, the radio signals from the GPS satellites will not be strong enough for your GPS receiver to receive them. If the power output ont hese satellites could be increased to a few thousand watts, GPS would probably be useable inside of buildings to about the same extent that cell phones are today, but there really is no way to be able to use GPS in drains or caves or tunnels. duck219 mentions some new technology that is being developed to fill this need. I don't personally know much about it, but I would theorize that it utilizes local transmitters at carefully located positions in lieu of orbiting satellites. If you had a few "satellites" located in carefully surveyed places around a cave (or drain), I imagine that a system could be built that would be able to resolve your position in the same way that GPS does. This would obviously not be anywhere feasable for exploring, since it would require lots of expensive equipment and careful surveying to provide coverage to even a relatively small area of a tunnel or cave (or drain). I have heard of people having luck with getting position fixes with GPS by poking the antenna through holes in grates and manhole covers. This obviously doesn't provide continuous location information like GPS does while walking around topside, but it will make it reasonably easy to connect the dots later on and figure out where you were in relation to topside topography. Just be careful not to get your antenna or fingers smashed by passing vehicles while huddling beneath a grate waiting for a position fix. Like a fiend with his dope / a drunkard his wine / a man will have lust for the lure of the mine "If you are not part of the solution, you are not dissolved in the solvent."

Finn location: Plano, TX Gender: Male \|	Re: GPS Device for Draining <Reply # 3 on 6/29/2005 9:07 PM >

	I was thinking about maybe using something like a pedometer to track how many steps we take and then use that to map it out on a street map. Anybody had any luck with that? Rest in Peace, Ninjalicious. I know that wherever you are, you're finding the best sites for us already.

NoSuchPerson Stop, or I'll ask you again! \|	Re: GPS Device for Draining <Reply # 4 on 6/29/2005 11:32 PM >

	You can get "dead reckoning" GPS units which will interpolate your direction...problem is, if you change direction without a satellite signal, the unit won't know this. As long as you walk at roughly the same speed, a pedometer would work, providing you have some way of knowing what direction you're going and when you make turns, etc... Then, when you're back above ground, figure out where you entered, set a waypoint on your GPS, then walk the exact steps you did underground, and turn exactly where you did. That'll give you "more or less" where you walked underground. You could try using a magnetic compass underground, but it might not work so hot, depending on the metal in the area, etc... But it's worth a try, I just wouldn't rely my life on it. -Ex Unit calling radio say again?

Finn location: Plano, TX Gender: Male \|	Re: GPS Device for Draining <Reply # 5 on 7/1/2005 4:44 AM >

	Yeah, compasses don't work so well down there. I think it has something to do with what the tunnels are made of. Maybe surveyer's equipment could get the job down as far as what angle the turns are. Rest in Peace, Ninjalicious. I know that wherever you are, you're finding the best sites for us already.

Chainsaw This member has been banned. See the banlist for more information. location: Underground, Colorado Gender: Male \| \|	Re: GPS Device for Draining <Reply # 6 on 7/1/2005 4:24 PM >

	I got a cheap laser/sonic measuring tape: http://store.yahoo...ol/st64latame.html The REAL laser measuring devices are quite pricey - this one just uses the laser for aiming and then uses sonar to measure distance to target. They aren't much good past 40-50 feet though. For around $500 you could get a real laser measuring device with a lot longer range (100's of meters) Quid latine dictum sit, altum sonatur.

lowkey Gender: Male \|	Re: GPS Device for Draining <Reply # 7 on 7/2/2005 6:58 AM >

	In the military during land navigation training, they teach you to determine distance by pace count. With a little practice you can get reasonably accurate. The trick is to use something like this to help keep count: http://www.actiong...og%2Fresults%2Etam Well that and lots of practice.

atomx

location:
Brighton, ON
Gender: Male

Re: GPS Device for Draining
<Reply # 8 on 7/2/2005 3:05 PM >

Posted by lowkey
In the military during land navigation training, they teach you to determine distance by pace count. With a little practice you can get reasonably accurate.

I learned how to do that back in Highschool doing my architectual/surveying class

"Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning." - Richard Cook

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