The Create Seawall Feature tool, found on the LP360 Feature Edit tab, allows the user to create a contiguous polygon feature at the proper width/depth and height of a seawall (or any similar feature) contained in the point cloud. This function can be scaled to fit the specific scenario of the user: from simple walls with a well defined point cloud to long contiguous stretches where the point cloud height is somewhat ambiguous. This function creates a 3D polygon at the height of the seawall, based on: conflation, user defined elevation, and some intelligent averaging to keep the height correct. This article reviews the setup and usage of this function:

Creating a Polygon Feature Layer for the Seawall Feature

The user will need an existing active polygon feature layer to use the seawall function. This can easily be created by using the “Create Feature Layer” function on the Feature Edit toolbar. The feature layer needs to be a 3D polygon. This will automatically populate in the Feature Edit toolbar as a layer.

Creating Conflation Point Cloud Task and using Auto-Z

The user will typically want to utilize a Conflation point cloud task to get the elevation for the top of the seawall from the point cloud while digitizing. In many instances, it will be beneficial to have multiple conflation tasks setup to use for different classification scenarios. The user can easily switch between these while digitizing by CTRL+left-click on the auto-z button to open the Feature Edit Options to set the desired conflation task to use while creating the seawall feature. Keep in mind that the auto-z function (if active) dictates the conflation used while creating a 3D feature.

Creating a Seawall Feature

Follow these step-by-step instructions to create a seawall feature:

1. Left click on the “Create Seawall Feature” button to start the tool.

2. Left-click in the map view in the middle of the wall feature to create the origin point. Once this initial click is performed, the user will see the location chosen in the map and profile view as well. From here the user can choose to alter the seawall elevation in the profile view, or continue digitizing in the map view:

The user now has two options for continuing:

1. Hold down the CTRL key when creating additional nodes in the map view. This allows the user to continue to create and confirm additional sections of the wall, even sections that are rounded and not straight. This can be as long as the user desires.

2. When finished creating sections, the user can perform a left-click in the map view, without holding down CTRL, to finish the wall section for this feature. Same as every node, the user will confirm the horizontal and vertical placement. The user now has the option of setting the width/depth of the wall length that has been digitized. This can be set in the map view by choosing the width visually and left clicking to confirm or by right-clicking to enter the depth in map units, press enter to confirm.

Now the user should have a 3D polygon that accurately represents the top of the wall. This function was originally created to be used with seawalls but could be useful for other features as well.

To build a top of Seawall Tool do the following:

1. Draw a profile box similar to the draw profile tool current in LP360. Double click to end using the existing depth, right click to specify a depth in a context menu, or rubber band the depth and left click to end.

2. The obtained line will use auto z to get a z value for the from and to points. The user is allowed to adjust these z values in the profile view.

3. Using an epsilon value above and below the resulting 3d line, query all of the lidar points from the active las layer that is within a 3d box formed by the 3d line and depth. Collect the min , max, and average z values.

4. Use the plane fit class to fit a plane to the queried points within the box. Adjust the from and to points of the 3d line to lie on the plane.

5. Write a polygon to a 3d polygon layer that is formed using the 3d line fitted to the plane and the depth. The line does not have to have equal z values along the line, but must be flat across the depth of the resulting polygon.