Minimum thickness of observable beds in different geologic beddings with variety of GPR frequencies
GPR is able to resolve geologic bedding due to changes in the velocity of the radar wave associated with changes in rock properties and because radar waves are reflected back toward the surface by some geologic contacts. In a practical sense, the thinnest geologic bed that can be observed by GPR is proportional to the average velocity of the radar wave in the subsurface, and inversely proportional to the frequency of the radar wave that the GPR system transmits. The minimal thickness of a bed that can be resolved is, roughly:
T_m = 1/2 * ( v/f)
where T_m is the minimum thickness of an observable bed (m), v is the average velocity of the radar wave (m/s), and f is the frequency of the radar wave (1/s).
As we can see, higher frequencies/shorter pulse widths are required to observe smaller features. This means higher frequencies are used for higher resolution surveys. This explains vertical resolution which is the smallest distance in the direction perpendicular to the surface that two targets can be apart for us to see them and distinguish them as separate objects.
This interactivable code confirms that geological beddings with lower electrical permittivity (higher GPR velocity) require higher minimum thichness to be detectable by GPR waves.
Trying different frequencies using the slide bar shows that higher frequencies observe smaller features or thinner layers.
As we can see in this plot, minimum thickness for very high saturated layer (fresh water) with 100 MHz antenna is almost 30 cm. But for the real average soil (with almost 0.1 m/ns GPR velocity) minimum thickness is almost 50 cm with 100 MHZ antenna. And for the void (air) the minimum thickness is almost 120 cm. For 900 MHz antenna minimum thicknesses are really low around 20-30 cm.
This code is written in P5. You can find more information about P5 javascripts here: p5js.org
The link to this bellow P5 code