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Technology for Mapping the Underground?
Archon-X asks: "As an avid CaveClanner, I spend my spare time sloshing around underground in drains, and have more than once considered 'mapping' the drains. How would readers approach this problem? Mobile reception and presumably GPS is non-existent, and it's pretty dark and wet down there."
Pen, paper & flashlight.
Seriously though.. You track around the sewers for fun? You seriously need a new hobby.
We started exploring mines, caves and soon included stormwater drains. These days, the Cave Clan have explored just about every type of artificial tunnel or chamber there is: bridge rooms, gas pipeline tunnels, purification tanks, sewerage discharge tunnels (disused), optic fibre tunnels, train tunnels, and many unnameable tunnels and cavities under the City.
For most mines and caves and such, if the company which bore the caves is still in existance, they may have maps and such for the caves and so on. If not them, then national archives. National archives or local government agencies may also have maps for the stormwater drains, as well.
Informatus Technologicus
Use GPS to map the locations of any openings where you can get a signal, IE gutter drains, manholes, etc. Inside the drains, use traditional surveying techniques. I am not a civil engineering major so I can't help you much there. You might also build some kind of radio location system based on the troglophone. That would be a very interesting project, although one that I would have absolutely no interest in :)
-73, de n1ywb
www.n1ywb.com
Depends what you're after. lots of string and a compass will give you distances and directions, used correctly.
to measure the size of rooms, check with architect friends about measuring all dimensions of a space manually
For crazy insane measurements of large caves, try surveyors tools.
If you're posting this on
mug
It is pretty dark and wet in the small intestine as well and these seem to work there. Perhaps it would help you out if you flushed one of these down the toilet and picked it up at the waste treament plan several hours later where you can get pictures of it's journey.
With a mean DM and you'll figure out the right and wrong way to map underground passages. What was the old rule, keep going left.
Start by walking around aboveground with a GPS, marking the locations of manhole covers, and other features that you should be able to identify when underground. Maybe drop some brightly colored markers down storm drain gratings to ensure you will know which grating you are under.
This should give you some points of reference that you can build the rest of your map around.
You might also want to plot those locations on a topographic map, or an arial photo, and play "connect the dots" to try to figure out a simple overview of how the drain system is layed out. Once you have the overview, you can fill in more details as you explore.
You could try using inertial navigation.
.... sorry, it's confidential information. :-)
There are some highly sensitive solid-state accelerometers. I believe that they are manufactured by National Semiconductor. Microsoft uses them in their handheld Sidewinder FreeStyle Pro. They look like fat silicon chips and the interfaces are digital, so they are easily connected to microcontrollers.
If you need higher precission, you could add gyroscopes. Laser gyroscopes are popular this days and their prices have come down quite a bit.
When you combine accelerometers with gyroscopes and a fairly high sampling rate, you can obtain high degrees of accuracy and precision.
If you can use waypoints, then you can calculate drift rates and improve accuracy. If you think that the GPS signal may be usable then you can use a GPS receiver as a waypoint source.
From my experience, the most common source of errors is high frequency content, specially when walking. A damper would go a long way towards improving the accuracy.
You should have no problem integrating everything into a small backpack with a laptop (if you need a UI), or a small shoe box if all you want is data logging.
Hope this helps, if you want more information such as part numbers and suppliers, I could gather some. As for designs and software,
Hector
take a reading every time you change direction.
gps has made people very, very lazy. navigation isn't rocket science.
Conformity is the jailer of freedom and enemy of growth. -JFK
That's not a goatse.cx link, is it?
I always thought that you could go down to the city hall and get city drainage plans...these days...i doubt that's the case...or a smart thing to do.
You could use a compass for heading, and a string for distance. I don't know how you would easily measure the length of the string though. Perhaps put it on a wheel with a counter? For straight shots, you could probably use one of those laser range finders...this would require two people, one at each end, but it might work.
I highly doubt the ultrasonic range finders would work. Too many reflections.
From my explorations...gps would be a no go. There just weren't enough manholes or drains. we only saw a couple, and you would have to open the manhole to stick the antenna out.
Hmm, I guess re-inventing GPS technology would be very expensive. Never mind!
Actually, there is good money to be made mapping and surveying these underground systems. Frequently the exploration is unmanned, such as dragging a camera through a sewer pipe checking for roots and cracks. In the industry they call these dirty movies . :-)
Get yourself an inertial navigation system from a submarine.
You could get eaten by a grue...
To map a maze of twisty passages, all alike:
What you'll need: Pen and paper, and lots of objects (at least one for every room).
What to do: Drop an object in the first room, which we'll call room #1. Make a note of what object you dropped in room #1 (let's say it's a sword). Put a '1' on the paper, with eight lines coming out at the compass points. Pick one at random (let's say north) and go that way.
You'll be in another room, which we'll call room 2. Drop another object (say, a bell), and make a note. Put a '2' on the paper, with eight lines coming out at the compass points. Finally, put a little '2' next to the line from room 1 you used to get here (in this case, north). You now know that going north from room 1 leads to room 2. Pick another direction (say, north again), and continue.
If you end up in a room without an object, it's a new room, and you repeat the instructions above. If it's a room containing an object you dropped, then you just need to make a note on the appropriate line from the old room. Pretty soon, you'll have the whole maze mapped.
Unless the thief comes by and picks up some of your objects. That'll mess you up. I recommend killing him first.
I've mapped many a storm system, and here are a few quick tips.
1.A compass works well in older systems composed of brick or clay tiles. Concrete pipe and box culverts often have enough iron in them to really mess up your compass.
2.Most cities have "Atlas sheets" available for all city utilities. Water, storm, and sanitary are often listed on the same sheet. You can usually find these at the municipal utility complex - for free. Just tell the clerk at the counter you are doing a topographic survey for new development, and need to show such on your plot.
3.I have used a cordless drill, concrete bit, and concrete screws to set points in the ceiling of pipes, at angle points. Use string and a protractor to measure angles. The screw also provides a nice hook to pull tape distances with. There is no way I'm taking a 20 grand total station into the sewer!
4.Put the tip and straw from a can of WD-40 on a can of funky coloured spray paint. Use the straw to spray out of the manhole lid. This can help you tie your underground survey in with aboveground locations.
5.Always be thinking like water. Water flows downhill. (duh) You aren't going to find that 10 foot dia. pipe very far from the local river or stream, or whatever your natural drain is. Take a johnboat or raft or such on a slow paddle down the riverbanks, looking for the big outlet pipes, and start your adventure there.
6.Methane or carbon dioxide poisoning is NOT a major risk in STORM sewers. Watch it in older systems, though. Many of the older ones are combined - still. If there is organic debris on the floor of the pipes you are exploring, that is also a cause for alarm about gas. Clean bottom storm pipes are almost always safe.
Those who said they have used GPS anywhere underground, near a lid or not, are full of it.
Who wants to carry a 4' level in the drains? What will you do with it? If you want to measure slope - get a combo compass/inclinometer or fancy yourself one out of the protractor you are using to measure bends.
Only one way to map a storm system - old school two man. Measure the angle and chain the distance!
You could do it like a real caver (i.e. spelunker). Here are some links: Good summary of technique , Some relevant books, A cave surveying mailing list, Some software to reduce your raw data, Links of links to more of the above and cave equipment suppliers.
Logic is not Divine.
No, really, it is called survex. Given data it attempts to construct a map of the cave allowing for inaccuracy. At least, so the author told me. I've got better things to do with my weekend than crawl around wet caves...
Doesn't the Tube (London Underground) already have one?
Actually, this is a project I've been dreaming about for a number of years. I'm a big Lego Mindstorms tinkerer, and have a fondness for sensing/mapping devices.
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In short, what I would propose is a pair of optical/LIDAR mapping units, with a tripod or other stable mount. One would also be equipped with a GPS for initialization. The way they would work is:
Set up the GPS-equipped unit outside the entrance to the underground system. Allow it to acquire a GPS fix to reference the entire system to the real world. This is optional if you don't care about georeferencing.
Next, set up the other unit just inside the entrance, within line of sight of the first unit. Trigger the second unit. It communicates with the first unit over short range digital networking (IR, Bluetooth, WiFi, FM modem). They negotiate who will go first. The winner begins firing a low-power IR laser 360 degrees panoramically around itself, waiting for the other unit to signal via the network that "I've been hit". When the hit is detected, the firing unit records the direction (angle/elevation/azimuth) to the other unit. Now, the two trade off, and previously firing unit becomes inert waiting to be struck by its mate. When it is, it signals its mate and they once again communicate the angles and bearing between them. They both perform a laser rangefinding (LIDAR) measurement to record the distance between them.
Now the spatial relationship between the two is known, and if the original unit outside the cave had determined its position by GPS, the real-world position of the interior unit can also be determined. Now, the outside unit can be packed up and moved.
At this time, the interior unit could be commanded (from a short distance, by a WiFi-equipped Palm or PocketPC) to perform a LIDAR vicinity scan, perhaps waiting a few seconds to allow the intrepid spelunkers to get out of the picture.
A vicinity scan would fire the IR LIDAR panoramically again, but not looking to hit the original unit, rather seeking to map the distance to the first obstacle in all directions, low, and high. Optionally, a visible light emitter and color sensor could record the color of the surface in each direction, creating a sort of panoramic Quicktime VR.
The mapping unit would signal when the vicinity scan was complete. The other unit would then be transported to a new location deeper into the complex, still within line of sight of the currently-parked unit. Once the deeper unit was securely parked on its tripod, it would be switched on, and the process begins again.
The deeper third station (actually the same hardware as the first station) calculates its position relative to the second unit, which now knows its position courtesy of the (now removed) first unit. It scans its vicinity, and adds the data points to the shared map (stored onboard, or on the controlling mapping handheld computer).
Lather, rinse, repeat.
Mindstorms are not sophisticated enough to do this -- too few IO ports, not fast enough processing to do real LIDAR, poor internode communications network. However, all of the individual techniques used in the design are singly possible with Mindstorms. All of the technologies together would be possible using a slightly more powerful development system (advanced PIC or Dragonball) and dedicated hardware. Accurate LIDAR systems are available COTS (Commercial Off The Shelf) but are pricey. A number of hobbyists use ultrasound for rangefinding. A combination of IR laser (for directional beacon) and Ultrasound (rangefinding) could be used to cut costs.
http://www.greenwich-observatory.co.uk/leicalrf800
http://www.ascscientific.com/impulse.html
http://www.rieglusa.com/
http://www.circuitcellar.com/library
-- There is no truth. There is only Perception. To Percieve is to Exist.
There are a couple of approaches. Having built and used an underwater cave mapper (The Wakulla2 Project) I know of what I speak. One of the guys (not directly involved with the mapper or rebreather of which I am one of the designers) has a technique for locating underground beacons using the Van Allen belt nulls. I do not know the details, but the technique also works in air caves. He places a beacon underground (in this case 300 ft underground and underwater) that is timed to go off at roughly noon. Noon is important for the null locator. It releases a powerful pulse that allows you to locate it on top. Then you can use GPS to get the position. If the drains and such were full you could use the cave mapper we built for Wakulla2. (About 1.5 M to build) I would point you at the site, but unfortunately, the site is offline due to funding. We were able to generate really cool 3-D maps of the cave system. The mapper used sonar to get the shape of the cave, an inertial guidance system (from an F-15) and the aforementioned beacons for synchronozation. It is also a self propelled device (oversized scooter). The data was logged and post processed, on the surface. The mapper is overkill, the the beacons would be a way of allowing you to get GPS data. The devices were moderately inexpensive, but they were all hand made by the designer of the technique. If there is a serious interest in the technique I can chase down who the guy was and were he lives now. Wakulla2 project was in the mid 90s.