GSSI SIR 30, Manual

Page: 38 / 150

Geophysical Survey Systems, Inc. SIR® 30
Manual
MN 93-101 Rev E 32
RADAR CONFIG > SCAN > DIELECTRIC CONSTANT ( 𝜺𝜺
𝒓𝒓
)
This parameter is used in the time to depth calculation that is applied to the vertical depth scale of the Line
Scan and O-Scope display. Selecting a value which approximates the dielectric constant of the media
under study will result in approximate depth values displayed on the vertical scale. If you choose to use the
Migration filter in Signal Process\ Advanced filters, the SIR 30 will use this value to perform the migration
process. This value is stored in the file header and can be modified in RADAN-7 post-processing software.
The values of the dielectric constant can range from 1 (air) to 81 (water). A table of values for common
natural and man-made materials can be found in Appendix D.
Figure 47: Radar Config – Dielectric Constant.
RADAR CONFIG > SCAN > POSITION MODE
This parameter allows the User to change the signal position in the time range window. The parameter
options are Auto or Manual. The Automatic Signal Position Servo will move the radar signal so that the
direct coupling (DC) will be at the top of the time range window. The servo will position the signal such
that 10% of the total time range selected is set above the direct coupling and ninety percent (90%) of the
time range is below ‘zero time’ In Figure 33 below the position mode is set to Auto. The time range has
been set to 10 ns. The surface percentage is set to 10%. The total time displayed is 9 ns. The total time
recorded is 10 ns. If the position servo is set to Auto, the User can adjust the displayed Surface percentage
between 10% and 5%.
Note:
If data is to be collected with low frequency antennas (200 MHz center frequency and below) at
long time ranges (> 200 ns) GSSI recommends that the Signal Position initially be set to Auto mode, then
changed to Manual mode. This will speed up the antenna initialization process.