Hello Piper and List
I used GPR before, and yes it has limitations.
1. It can't see past the water table, blocks the signal, or reflex
signal completely, and you see nothing past it.
2 Wet and dry clay soils weaken and/or block the signal completely, you
send out a signal and it doesn't come back.
3. Depending on the frequency, Units can see small objects close to the
surface, deeper you go, the large frequency you need, and only large items
can be seen at great depths, the unit I used range between 1 to 45 foot
depths, It's seen 3' dia. manhole covers buried 25' deep, but not 8" valve
covers at that depth.
4. Metal objects vibrate, they stand out great, stony meteorites don't
stand out well, I tested it on some, But you can see the changes in the
layer of bedding, the bedrock and the disturbance of the impact on them,
5. Most GPR units only work looking straight down, so the area needs to
be flat and level for best results.
Hope this helps, good night all.
Thanks for your time
Keith
Chandler AZ
----- Original Message -----
From: "Piper R.W. Hollier" <[EMAIL PROTECTED]>
To: <meteorite-list@meteoritecentral.com>
Sent: Friday, October 05, 2007 11:30 PM
Subject: [meteorite-list] Ground penetrating radar at Carancas?
Hello again list,
Ground penetrating radar (GPR) is commonly used for non-destructive
investigation of archaeological sites. GPR "can detect objects, changes in
material, and voids and cracks." (Wikipedia) Has anyone thought of mapping
the crater with GPR before sending in a backhoe to rip it open? This could
be one way to have some idea whether there are meteorite masses under the
ground, how large, and where, before starting to dig. It could also yield
valuable information about the morphology of the crater, with potentially
more precision and detail than digging would allow.
Can someone on the list comment on the state of the art of GPR? How deep
can it penetrate nowadays? (Wikipedia says 15 meters, best case.) Would a
high water table be a problem? (Wikipedia says that range would be greatly
reduced in "moist and/or clay laden soils.") Are there new designs or
techniques that could get around such limitations?
In any case, there would be some thorny practical problems to be dealt
with. Ordinarily the antennas need to be nearly in direct contact with the
ground, which would seemingly make it very difficult, if not impossible,
to do a scan of an area where the ground surface is anything but flat. Or
has someone come up with a "workaround" for this issue in a similar
situation?
Best wishes to all,
Piper
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