Zonge GDP-32 - Page 273

NATURAL SOURCE MAGNETOTELLURICS
Section 13, Page 5 May 2002
default and should be used for normal operation. The RECTANGULAR window can be used
when detecting synchronous signals (same frequency as the GDP time base).
Robust Processing: Turns on and off the robust processing mode with the
following parameters. This menu is displayed only for the vector mode of operation.
Note: Robust processing is turned off in the GDP-32
II
at this time, while software
modifications are being made.
Coherency Limit: .90. This is the coherency coefficient limit that can be manually
set from .00 to .99. This parameter is used in the real-time data acquisition mode to improve
the data quality. Default is 0.9. It is suggested that you do not lower the limit past 0.5 for
normal data acquisition.
Coherency for the E
x
H
y
component is defined as:
|E
x
H
y
*
|
2
——————
H
y
H
y
*
⋅
⋅⋅
⋅ E
x
E
x
*
where E
x
E
x
*
, H
y
H
y
*
, and E
x
H
y
*
are average auto-powers and cross-powers. The same
formula is used for the E
y
H
x
components.
Outlier Rejection: ON. Turns on/off the outlier rejection option.
Outlier rejection: 2 times median. Specifies the rejection limits for the
outlier rejection option.
Channel to monitor: 1. Specify the E-field channel to monitor for coherency
acceptance. This is valid only for Scalar data acquisition.
Gain Mode. The default mode is "Very Noisy", which limits the gains to obtain
a maximum voltage of 0.5 Volts, leaving adequate headroom for SP drift and random noise
spikes. The other option is "Noisy", which adjusts the gains for a maximum voltage of 1.0
Volts. See Section 6. Noisy gain mode should be used under normal circumstances to
provide sufficient margin for telluric drift.
Units. The operator can select meters or feet. The default is meters.
Save data on disk: ON. This indicates that the operator wants to save the raw time-
series data on disk for further processing. This data will be stored to disk prior to internal
GDP processing.