NATURAL SOURCE MAGNETOTELLURICS
Section 13, Page 27 May 2002
The first line contains various non-channel specific parameters for the data block. On the first
line, the first value (5) is the number of channels of data that was gathered, next is the number of
data points (4141) in the time series for one channel. Next, is the sample rate log base 2 (12) and
the following value is the field data cache block number. If there are more than 4 channels of
data then a 0 will be written in those columns on this line.
The sample rate value determines which of the four frequency bands this time series file
represents: very high (384 - 8192 Hz), high (48 - 1024 Hz), medium (3 - 64 Hz), or low which
ranges from 4 Hz to a possible low frequency of 0.0007 Hz. Sample rate for the low band is 16
Hz (log base 2 is 4), medium band's sample rate is 256 Hz (8), high band is 4096 (12), and the
very high band has a sample rate of 32768 Hz (15).
The second line contains the GDP-32
II
actual channel number minus 1 that this column of data
represents.
The channel designator is on the third line, where 1, 2, 4, 5, 6 represent Ex, Ey, Hx, Hy, and Hz,
respectively.
Station number for Ex and Ey channels or antenna identifier for Hx, Hy, and Hz channels are on
the fourth line.
Line number 5 has the A-spacing used for Ex and Ey or the channel number used as the remote
reference for Hx, Hy, and Hz channels. In this example, remote reference was not used so
default values were written.
The last header line contains the conversion factor from time series data to volts.
Then, line 7 to the end of the file contains the raw time series data for each channel. In this
example, there are 4141 data points so there will be 4138 more lines of time series data.
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