(Creating) Low Cost REAL GPR

[Funfinder]

Ground Penetration Radar means it works like a Radar - not as a metal-detector!


Real GPR works from ca. 10 MHz (large antennas, deep, low resolution) to 1,5 GHz (small antennas, shallow, high resolution).

It really measures the timing, shape, amplitude, energy, phase etc. of the transmitted wave which gets "reflected" if the ground or soil etc. changes.


Usually 2 dimensional slices of the ground get created (but those are combinable to 3D pictures):

The persons stands with the device at one place and receives a single depth-analysis of the penetrating spot up to 30 meters if he uses 10 MHz
and if the ground is OK for this - with higher frequencies and easier usable devices (small antennas) the depth is 5 meters to only ca. 50cm.

Next he moves on in a straight row or circle shaped form to other nearby spots and measures the ground there.
The final result is like a track with shown depth-anomaly values.
If the person walks close this track and creates more such nearby tracks he will get a 3D visualization of the ground if the software can render it.
Many times the graphic becames a better recognition-design with different colors for special high and special low "frequency-activity" spots.


I wonder what's needed to create such a "echo-timing-meter" much easier and just for around 1000 bucks compared with the real expensive stuff.
Almost anybody has a bluetooth smartphone or laptop anyway so all what is needed is the transmitter, the "receiving-timer" and
the analog-digital converter inclusive the smartphone or laptop software that records and shows the incoming signals on the screen.

[HiiiQ]

EM travels very fast so "slicing " the return signal into time intervals would require expensive hardware and lots of technical experience. What you are proposing could be more easily with generating sound waves and "reading" the reflected signal trough some free osciloscope or audio prosessing software.

[homefire]

Could a Fish Finder set up be incorporated? Convert the Radio waves to Ultrasonic and displayed? Problems I foresee would be the fish finder bases the return signal on the Tx signal. How to deal with the delays of converting one to the other?

Perhaps a Buffer could be used to correct for the Delays?

[Silver Dollar]

Well the earth is rather solid, to put sound into it you need a big hammer. Ultrasonic's won't penetrate very far.

A fishfinder is directly connected to the contiguous medium of water. Again you won't get any penetration in
earth (unless it is very saturated with water.

A real GPR isn't too hard to make the pulse can be similar to a PI type. The trick is in the post processing to get
a XY plotted view of the acquired data

[Davor]

And most nowadays radars are just quasi resonant devices that use antenna bandwidth as a pulse shaping method.
There are some "holographic" methods that are less broadband, but I'm too lazy to even start playing with those.

There are some 10GHz radar units mass marketed as Doppler sensors that work in CW and pulsed mode. Guess such radar unit (cheaper than 20$) can be attached to a rod and when swinging it you should hear Doppler responses by your bare ears. A little processing should give you a holographic display of the ground. With nowadays inertial sensors it should not be too difficult to achieve.

[Silver Dollar]

I worked on GPR's at one time. We used a transistor in avalanche to generate fast pulse.
The pulse was then filtered through different size antenna's to get different frequencies.
A DSP board then filtered the data and it was output on a color screen. Nowadays DSP
is much cheaper and easier to implement.

Caution Shameless Plug!

You could possibly make one using this bare board I have for sale;
http://www.geotech1.com/forums/showt...dec-Bare-PCB-s