Step-Frequency Tecnology

Conventional GPR antennas emit a quasi-monochromatic electromagnetic pulse around a certain frequency. As a consequence, the bandwith (difference between the maximum and minimum radiated frequencies) is very narrow, thus limiting resolution (minimum size of a detectable object).

The Step-Frequency technology is based on emitting a continuous radiation with a time-increasing frequency. This produces a broader frequency spectrum than the one obtained with traditional antennas. Current GPR equipment allow to record data from 100 MHz to 3 GHz. If a similar bandwith dataset was to be achieved using conventional monochromatic antennas, the survey would have to be repeated several times using each time a different antenna, with the associated increase in economical costs.

3D Models

For the construction of a three-dimensional GPR model it is necessary to acquire several profiles sufficiently close to each other. 3D-Radar antennas are composed by several sensors that record data simultaneously, reducing significantly acquisition time. Three-dimensional models improve our understanding of the subsurface making interpretation simpler and achiving consistent and robust results.

3D-Radar antennas are composed by up to 29 channels, separated 7.5 cm, covering a swath of 2.1 meters wide with every run.

The use of this equipment has three advantages:

1. Absence of paralleling errors between channels.
2. Significant reduction of field acquisition time.
3. More reliable interpretations.

CMP

The CMP (Common Mid Point) is a well known method to calculate the propagation velocity of an electromagnetic wave. The method has been widely used in seismic applications for decades and it is based on recording signals with an increasing distance between transmitters and receivers.

GPR wavespeed calculation is very important for two reasons:

1. It allows a precise conversion from two-way-traveltime to depth. Thus, the depth estimate at which anomalies are located beneath the ground is very accurate.
2. It provides information about composition, humidity, etc.

Our 3D-Radar equipment allows us to record continuous CMP data therefore producing a continuous profile of the GPR wavespeed.