GSSI SIR 20, User Manual

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Geophysical Survey Systems, Inc. SIR® 20
Manual
MN92-078 Rev F 23
4
Even though the Configuration Window will show options for Scans/Ft, that parameter has no affect
on time-based data collection. The most important collection parameter is Scans/Sec. This is the
number of scans that your SIR 20 will record every second. The most common method for
determining the correct number is to figure out how many scans per unit distance you want and
compare that to a comfortable walking pace. For example, 12 scans per foot is desired and the
operator will walk at 3 feet per second. The Scans/sec should then be set at 36.
5
Once you have made changes to the collection parameters, follow Steps 8 and 9 of the Survey Wheel
Controlled Collection setup.
During Collection
•
During time-based collection, you can stop moving at any time, but the
SIR 20 will continue to collect data. You can interrupt data collection by
clicking the pause button on the collection toolbar, or by holding down the
marker button on the antenna tow handle for at least 3, but no more than 5
seconds.
•
Clicking the marker button on your antenna tow handle or the down arrow
on the laptop keyboard will put a mark (dashed line) in the data. This is
useful for noting features of interest at your survey site and for marking the
linear distance surveyed.
•
You can end the survey by clicking the appropriate button on the collection toolbar. You can also
close and save the file by holding down the antenna tow handle marker button for 5 seconds.
•
To collect another profile with the same settings, click the Run Project button (green square).
Point Mode Data Collection
This data collection mode is very similar to survey wheel and time-based collection. Point data mode
collection is usually performed with large, low frequency antennas or with two similar antennas in a bi-
static configuration. When two antennas are used, one acts as a transmitter and one as a receiver.
Typically point data is collected at discrete stations spaced at a constant separation which will produce a
file with a linear horizontal scale. Care must be taken when selecting the scan spacing. If too small a
number of traces per unit distance are collected, the profile will be under-sampled and you could miss
targets of interest. If too large a number of
traces are selected, the data file will be over-sampled. This will
generate a very large file and can significantly increase in the time to collect the file.
1
Create a new collection project by going to File > New or clicking the New Project button on the
collection controls bar. This will open a window with the heading Create New Data Collection
Project (Figure 21).