Detect Shoals

The Detect Shoals command is used to identify shoals in the currently selected surface. A shoal is an area where sedimentation and/or deposited objects cause bathymetry to no longer conform to the expected reference model. This excess material is a hazard and must be addressed to allow normal usage of the waterway. In the mean time, however, mariners must be informed about these exceptions to the model.

Shoals should only be detected on bathymetry with true depths. You should not detect shoals on a difference surface or other files that do not contain true depths.

• A CSAR file (.csar) containing the bathymetry around the shoal areas as it was at the time of detection

The shoal boxes are created parallel to the alignment in the station catalogue based on the shoal areas grouping and the splitting interval. There can be multiple area groups in a single survey. The groups can be changed manually if necessary. See Group Areas for more information.

• Calculate Clearances	• Group Areas
• Change Status	• Import from Database
• Classify Boxes	• Merge Boxes
• Determine Reference Features	• Register in Database
• Display Depth Annotations	• Reorient Boxes
• Edit Record Association File

Option	Description
Station catalogue	You must select a station catalogue in order to associate the shoals with the current reference model. The station catalogue contains: • the alignment that is used to determine shoal orientation, • the template that is used to determine the reference depth and shoal clearances, • the reach that is used to identify the area in which the shoal was found, and • the partitions used to determine shoal severity classifications. This selection will be remembered in other shoal-related dialog boxes used in future procedures. Only station catalogues with a single alignment-template pairing are available to be selected in this dialog box.
Automatic shoal merging and subdividing	During detection you can have shoals automatically grouped, split and/or merged based on the size and location of each shoal. Select this option to turn on automatic merging and subdividing.
Group areas within	Grouping causes shoal areas to be assigned to the same group of boxes if the areas are within a user-specified distance of each other. 1. Enter a distance value in the text-entry box.
Split boxes at each	Splitting causes shoal areas to be created at each multiple of a user-specified interval value. This allows the shoal areas that are more critical to be displayed separately from the areas that are less shallow. 1. Enter an interval value in the text-entry box.
Merge boxes thinner than	Merging causes shoal boxes to be combined if they are smaller than a specified value. 1. Enter a size value in the text-entry box.
Output file	The name and location for the resulting shoal layers and files. Click the browse button (...) to launch a standard Windows Save dialog box and define a name and location.
Minimum depth precision	The number of decimal places to include in the Minimum depth value of shoal boxes. The default value is 2.

1. In the Layers window, select a layer with depth values from the surface for which you want to identify shoals.

The shoals are detected and saved. Layers are added to the Layers window for each of the shoal feature types.

Menu	Tools > Engineering Analysis > Shoals > Detect Shoals
Tool