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5 beam snippet intensity – Triton Isis User Manual

Page 264

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June 2004 Isis® Sonar User's Manual, Volume 1

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Right-clicking in the Multibeam Intensity window summons the standard
Waterfall Display dialog box (Figure 10-2), where you can make certain
adjustments to change the look of the imagery.

10.4.5 Beam Snippet Intensity

This Multibeam Bathymetry function, accessible from Window

Multibeam

Bathymetry

Beam Snippet Intensity, can display and log Reson snippet

data.
Snippet data refers to time-series backscatter data that is acquired near the
bottom detection of each multibeam beam. By stitching together these small
views of the bottom, a pseudo-side-scan record can be created. There is
significant processing involved because the snippet fields overlap spatially,
and they’re taken at an irregular angular interval. As a result, careful
attention must be paid to the manner in which the backscatter samples are
displayed. Since the final image is produced from a lot of little beams
pointed down, rather from a wide beam formed for a dedicated side-scan
image, a cleaner image is possible.
The term “pseudo-side-scan” record is used here because true side scan
represents a continuous time-series of data from point of transmission to
farthest return, including water column. With this technique, the water
column isn’t present and must be inserted artificially because the snippet
data is taken near the first return of each beam as it strikes the seafloor.
Sea tests with the software show a cleaner image in the data. There are,
however, occasional data drop-outs where a beam doesn’t get good bottom
detection. Because snippet samples overlap from beam to beam, multiple
consecutive beams must lose bottom lock in order for the image to degrade.
For example, you might use the snippet feature this way:

1. Acquire the snippet data over, say, a dedicated IP port on an existing

LAN interface. Sidescan and bathymetry can come over simultaneously
on the same network connection.

2. Store the data in XTF.
3. Process the snippets into a sidescan-like record.
4. Display the data.
5. Mosaic the data.

This all happens simultaneously with the normal sidescan and multibeam
acquisition and processing, so there’s a lot going on at once.

Chapter 10: Using the Window Menu