News Item: Ground Penetrating Radar
(Category: Other news)
Posted by imperio
Sunday 13 June 2010 - 19:09:01

Home-made, Ultra-Wideband, Short-Pulse GROUND PENETRATING RADAR made by bulgarian engineer Petar Valchev

This ground penetrating radar (GPR) has been designed specially for treasure hunting. The GPR can find subsurface heterogeneities, such a cavities, tunnels and other objects. All GPR are excellent to survey in rocks and sands, good in rather dry soils without clay, and useless in soil with clay and wet soils .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 XP or Vista, 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. When 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 metre.



GPR tested by Aemilivs



The antenna system is dipole, unshielded, air coupled.


Antennas:
75MHz - length-1,5m, depth-6m, resolution-1.5m Current consumed - 0.3A from 12V battery
100MHz - length-1m, depth-5m, resolution-1m Weight - kg 4 with battery
150MHz - length-0,75m, depth-4m, resolution-0.8m More suitable is antenna 100MHz
250MHz - length-0,5m, depth-2m, resolution-0.5m
350MHz - length-0,3m, depth-1.5m, resolution-0.3m




Depth - detection depth - Distance between ceiling of a cave in rock(limestone) and ground surface . If a ceiling is flat and cave=4x(Antenna resolution) . Depth is dependent on the parameters of the rock or soil.

Manufacturers advertise for similar antennas 150Mhz depth from 7m to 10m, but with a small letters write 'Depth of investigation is understood to be detection depth of a flat boundary with reflectance equal to 1'. But reflectance equal to 1, have only metal flatness 4m X 4m, or a lake bottom. A cave in limestone or dry Soil, have reflectance equal to 0.4 and then 10m x 0.4=4m, but it is true if the cave is big and have a flat ceiling.



Front panel







Bulgarian engineer Petar Valchev


The GPR can detect cavities in rather dry soil without clay with dimensions width Xm, length Xm, height Xm on depth Xm. As an example if the cave have width 2m, length 2m, height 2m and flat or oval ceiling, GPR will be able to detect the cave on depth 2m in soil. m=metrРµ 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.
Since 04-20-2009 the depth is increased 20% for big objects and 50% for small objects.
Since 01-06-2010 the software is upgraded , added the gray scale mode, time window 25nS and speed control.

Read more in forum: [link]


This news item is from METALDETECTING PORTAL
( http://mail.metaldetectings.com/news.php?extend.34 )