User's Manual

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18
Antenna Handles are used when profiling without the use of
Skid Box or Antenna Sledge. Use of the handles is
recommended mainly for the low frequency antennas where
the station separation is comparably great. For more
information see Chapter 10.
4.3 Operation modes
The unshielded antennas can be operated in a variety of
modes for different survey techniques. They are:
?? Reflection profiling: This is the most common type
of operation. The antennas are mounted at a fixed
separation and moved along a line. Measurements
are taken at even distance or time intervals.
?? Velocity profiling (common midpoint (CMP) or wide
angle reflection and refraction (WARR) type of
profiling): In order to calculate an accurate depth
scale the measured reflection times must be
converted to velocities of the radar signals. This
conversion can be made empirically by assuming a
velocity based on experience or existing data such as
the relative dielectric permittivity of the medium being
surveyed. Otherwise, the radar velocity can be
calculated by measuring time delays of the reflected
signals as various transmitting and receiving antenna
offsets.
?? Cross-scanning (tomographic type of profiling):
Cross-scanning is a technique used to investigate
e.g. the integrity of an area located scanning
between the antennas. This can be e.g. concrete
constructions or a rock mass between two tunnels.
RAMAC/GPR allows you to collect cross-scanning
data that needs to be processed in external software