Duilio,

What you describe sounds practical but rather difficult to make. If a plan
of the route would be enough (at least to start with) then another option
may exist.

Drain cleaning machines can usually push a long "rod" down a drain. If you
placed a signal generator at the end of the "rod" which produced a short
range RF signal you should be able to locate its position quite accurately
with an above ground search coil. I believe that very low frequencies are
better at ground penetration - essentially a high frequency audio oscillator
driving a suitable coil.

I imagine that GPS would be totally unsuitable for underground use.

The device that you described is a full "inertial platform" - such devices
are available pre-built from companies such as -

i    Systron Donner
        www.systron.com

ii    Crossbow (no URL sorry)

iii    Also possibly suitable equipment from -

    www.primenet.com/~watgyro/Ramenskoye/products/gvk-10.html

    www.fibersense.com/index.html

    www.microsensors.com/products.html

Tokin ceramic gyros

 www.tokin.com/Tokin_America_Products/p46/p46.html

Murata piezo gyros

     www.murata.com/develop/index.htm
     www.iijnet.or.jp/murata/index.html


www.murata.co.jp/Ceramy/owa/CATALOG.showcatalog?sHinnmTmp=ENC-03J&sLang=2

     www.nerorockets.org/haarlem/hegyro.htm






      Russell McMahon
_____________________________

>From other worlds - www.easttimor.com
                                www.sudan.com

What can one man* do?
Help the hungry at no cost to yourself!
at  http://www.thehungersite.com/

(* - or woman, child or internet enabled intelligent entity :-))


-----Original Message-----
From: Duilio Foschi <foschid@SHUTTLE.ETRURIA.NET>

>I live in Italy in an old apartment building (once a barn) built about 400
>yrs ago.
>Nobody knows the exact route of the sewer pipe. We only know the location
>of the last drain well.
>Due to a court litigation, we need to ascertain the route of the sewer
pipe.
>The only way known here is to begin digging from the drain well and follow
>the sewer pipe up to the main sewer pipe (the one owned by the city) buried
>somewhere under the street level.
>
>This would be very expensive, as it means breaking the floors of the shops
>located at ground level and stopping their activity for several days.
>
>I guess that someone must have built a simple device fitted with a
>gyroscope and an inclinometer that can be inserted in the drain well and
>follow the sewer pipe.
>
>The device will transmitting back infos by wire and a PC will be able to
>draw the route of the device, i.e. of the pipe.
>
>A jet of compressed air could be the chosen locomotion system.
>
>I heard that oil companies use this mousetrap, so someone out there must
>build and sell it.