3
Cross-Section Analysis
The "Cross-Section Analysis" section of this report demonstrates the tools
associated with generating cross-section plots from imported ADCP data. This tool
allows the user to select data points from a plan view window to create the cross-
section plot. The data can be selected along the transect line where they were
collected or they can be selected at any angle to that line. Because the data is
spatially tagged, cross sections can be generated from any set of points. This is a
very powerful tool in that it allows the data to be viewed from any direction.
Generating Cross Sections
To generate a cross section from a transect, the desired data set should be
active. Click on the Generate Cross-Section tool (Figure 3-1). The user is prompted
to draw a polygon around the transect points (Figure
3-2). Define the polygon by clicking and double-click
when the polygon is completed. Data points can be
selected along the transect or across transects as
shown in Figure 3-3.
Figure 3-1. Generate
cross-section tool
Figure 3-2. Instruction message box
HyPAS asks the user whether to horizontally average the cross section (Figure
3-4). See the notes from the Plan View Vectors section of the previous chapter for
information about horizontal averaging. If user responds af firmatively, a distance
between points will need to be provided (Figure 3-5). A negative answer prompts
the user to enter the starting point after HyPAS has extracted the data. This prompt
is in the lower left corner. The user will know that HyPAS is ready for the starting
point when the cursor returns to a cross hair. Click on the starting point for the
cross sections. By defining the starting point, the user defines the orientation of the
cross section, thereby, establishing a point of reference determining the direction of
view. Therefore, the user can determine whether the user is looking into the
channel or into the bay.
3-1
Chapter 3 Cross-Section Analysis
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