In this section:
Introduction
This command will generate classificated points for the selected chart(s).
Input to the classification algorithms are the grids called Seafloor that are located under each "chart name" folder.
The Points Classification dialog
The content of the menu
The classification options are: Shoals, Deeps, Saddles, Ridges and Valleys
The points ar defined as:
- Shoal point: The shallowest point (node or sounding) in an area. All surrounding nodes are deeper.
- Deep point: The deepest point (node or sounding) in an area. All surrounding nodes are shallower.
- Saddle point: The shallowest point (node) in a fairway. The surrounding nodes are deeper on two sides and shallower on the two perpendicular sides.
- Ridge point: A break point (node) on a ridge. The surrounding nodes are deeper on three sides and shallower on the fourth side.
- Valley point: A break point (node) in a valley. The surrounding nodes are shallower on three sides and deeper on the fourth side.
Classification points
Set the correct parameters for the selected options and click Execute.
The result is a set of points that tells where the selected classification points are located. The classification points are saved under the <chart name> folder and a <classification>
folder with the name of the option and the parameters selected.
The parameters are set in the four tabs: Shoals/Deeps, Saddles, Ridges and Valleys
The Shoals/Deeps ta
Shoals
Will find those grids nodes that are the shallowest within the Minimum distance.
The option Mask width is a mask moving over the grid and checking the centre node with the nodes around.
A shoal is detected when the centre node is shallower than the rest of the nodes in the mask. After the detection the points are sorted on increasing depth values, and by starting with the first (and shallowest) point, all points with a distance smaller than the Minimum distance will be removed. Then the same test is performed for the next valid point, etc.
The shoals are saved in <chart name> classification shoals_<filter width>_<distance>.
Deeps
Will find those grids nodes that are the highest within the Minimum distance.
The option Mask width is a mask moving over the grid and checking the centre node with the nodes around.
A deep is detected when the centre node is deeper than the rest of the nodes in the mask. After the detection the points are sorted on decreasing depth values, and by starting with the first (and deepest) point, all points with a distance smaller than the Minimum distance will be removed. Then the same test is performed for the next valid point, etc.
The deeps are saved in <chart name> classification deeps_<filter width>_<distance>.
Ridges
Will find those grids nodes that define a ridge. The two parameters are the
maximum ridge angle towards the shallow area and the minimum ridge angle towards the deep area.
Saved in <chart name> classification ridges_<maxshallowangle>_<mindeepangle>.
To see all ridge points set maximum ridge angle towards the shallow area = 90, and
minimum ridge angle towards the deep area = 0. Default setting is 20 and 5.
Test and tune the parameters to get the proper ridge points.
Saddles
Will find those grids nodes that have two low and two high neighbour points.
If the search radius is greater than zero, the lowest saddle point within the search radius
will be selected.
Saved in <chart name> classification saddles_<searchradius>.
Valleys
Will find those grids nodes that define a valley (which is the opposite of a ridge).
The two parameters are the
maximum valley angle towards the deep area and the minimum valley angle towards the shallow area.
Saved in <chart name> classification valleys_<maxdeepangle>_<minshallowangle>.
To see all valley points set minimum valley angle towards the deep area = 0, and
maximum valley angle towards the shallow area = 90. Default setting is 5 and 20.
Test and tune the parameters to get the proper valley points.
Find corresponding points in Soundings
This option enables a search in the Soundings dataset for the nearest point that was found in the Seafloor grid. The corresponding points are saved in <chart name> classification <type>in_soundings<parameter>.