Gemini Software Operation
Gemini Profiling System
0695-SOM-00001, Issue: 03
49
© Tritech International Ltd.
The above example shows the fixed sound velocity selected, and a value of
1499.2m·s
-1
will be sent to the Gemini Sonar. The software will round the value
entered and the actual value used will be displayed on the
Sound Velocity
display on the
User
screen.
When using a fixed sound velocity, the software will check the value entered and if it
falls outside the range 1400m·s
-1
to 1588m·s
-1
, it will give a warning to the user and
use a default value of 1499.2m·s
-1
.
12.4.4. Compression
Run Length Encoding (RLE) is a technique that is used to compress the image data
as it is transferred between the Gemini head and the software, thus reducing the
bandwidth required on the connection between the two. RLE in Gemini is a lossy
compression technique, a level can be applied which means that all data below that
level is set to zero and then the compression is applied. Increasing the RLE level will
increase the efficiency of the compression (and hence reduce the bandwidth required
to transmit the image data) but will remove more and more of the lower levels from
the data (initially reducing the noise but quickly removing smaller objects/weaker
targets from the image).
Enable Compression
toggles the compression when clicked (black background
to the button means compression is off, blue background means compression is on).
The
Compression
control sets the level applied by the run length encoding; this is
the value below which the data is treated as zero rather than the actual data value.
The live image displayed by the Gemini software shows the effect of the compression
immediately.
Note
The compression is applied in the link from the Gemini head to the
software, therefore compression cannot be applied to data that has already
been recorded, and if data has been recorded with compression applied,
the compression cannot be removed from the data.
Note
RLE applies to the image data only and has no effect on the digitised
targets.
