GROUND  PENETRATING RADAR

             GPR technology is suitable for detecting large cavities such as caves, rooms, tombs and tunnels in high resistivity environment as massive rocks,  soils without clay and very dry sand.  Usually GPR does not penetrate into ordinary soil(farm soil, garden soil), because soils almost always have good electro conductivity, and radio waves do not penetrate into an electrically conductive environment.  There are soils in which GPR technology penetrates, but they are rare, in Bulgaria they are extremely rare. That's why I recommend GPR only for high resistivity environment as massive rocks and very dry sand, for survey in soil click on Earth resistivity meter .    The obtained information immediately appears on the laptop display. The GPR can find good, subsurface cavities larges than 1metre x 1m x 1m, with an almost flat ceiling. Smaller objects will be  found with difficulty and not so deeply. The laptop can be any , with Windows 10, and USB port , 1.4GHz or more.The GPR can to be carried by a single operator. In the sounding process, the operator is getting real-time information as a radiolocation profile (radargram) on a display (on a notebook). The GPR draw the radargram for 60 seconds (in this time operator can see the received part of the radargram) , after that operator can record it on a hard disc with any name for further use, or/and start new.  The GPR can scanning with the time window(time that gpr receive after transmit pulse) 50nS, 100nS or 200nS.Wen the operator carry the GPR, antennas must be from 5 to 20 centimetres over the ground surface. Distance between antennas can  be from 0.5 to 1.5 metеr

The antenna system is dipole, unshielded, air coupled.

Antennas:

75MHz - length-1,5m,  depth-10m                      

100MHz - length-1m,    depth-8m                                

200MHz - length-0,5m,  depth-4m  

350MHz - length-0,3m,  depth-3m

 Current consumed - 0.3A from 12V battery

Weight - kg 4 with battery

Depth - detection depth - Distance between ceiling of a cave in rock(limestone) and ground surface . If a ceiling is flat or oval and cavity is large .  Depth is dependent on the parameters of the rock or soil.

With the GPR you will be able to detect cavities in rock or sands with dimensions width Xm,  length Xm,  height Xm at a depths 2*Xm. As an example if a cave have width 2m,  length 2m,  height 2m and flat or oval ceiling, the GPR will can detect the cavities on depth 4m in rock.

m=metrе

If the ceiling is not  flat or oval, or is acute, the depth is smaller.

When the soil is wet, the depth is smaller. In practice it is very  difficult or impossible to predict how deep GPR can see in soil because it is depend from soils characteristics. 

In the "WORLD ATLAS OF GROUND CONDUCTIVITIES"

http://hamwaves.com/antennas/gnd-sigma/vlf_mf_ground_conductivity_atlas.pdf

you can to see if your region is suitable for GPR survey, if a GPR will have good depth.

      If ground conductivity is less than 1mS/m the conditions are  perfect.

      If ground conductivity is more than 10mS/m , GPR will be useless in this region , you can to use a GPR only  in  rocks in this region.

      Unshielded antennas 

Shielded antennas

1600 MHz GPR antenna

3D visualisation

Examples

       Earth resistivity meter                    https://sites.google.com/site/resmeter/home

      Transient Electromagnetic system https://sites.google.com/view/tdtem