Hello TBC’ers! Feature extraction is one of my favorite tool sets within TBC, and there are so many ways to incorporate it into your workflow. This week’s tip is focused on one type of point feature extraction, specifically manhole, which was released in TBC version 5.80. Read the release notes here to learn more, or check out this video walkthrough!
1. To start this workflow, select the “Point Clouds” tab (1A) and click on the “Extract Point Feature” (1B) in the extraction section.
2. This will open up the “Extract Point Feature” pane where you can select which type of extraction you want (2A). There are two different options for manhole extraction (photogrammetry and laser scanner) which were included to help ensure accurate results based upon how the dataset was collected. In case of photogrammetric point clouds, use the “Photogrammetry” option, as long as the flying height is adequate enough to create clearly distinguishable features. All other types of data collection, such as terrestrial scanners and mobile mapping data should use the “Laser Scanner” option. For this example, we are using “Manhole - Photogrammetry”.
3. From here, there are two options for proceeding. The user can either manually identify each manhole, or use an automatic extraction method (3A). First we will cover manual extraction, then in steps 6-7 we will cover automated extraction. It is important to note that the point cloud of interest must be activated in the “View Filter Manager”, and it may help to disable point cloud regions that do not contain manholes.
4. With manual extraction selected, click in the “Pick a point…” (4A) box and select a manhole you want extracted from the plan or 3D view. When using the manual extraction method, the user is able to click anywhere within the feature and both the center and perimeter of the manhole will be identified. This will populate the “pick a point” box with the newly identified manhole, and the next step is to press “enter” or click on the “Extract Manholes” button (4B).
5. Next, edit the new features point ID, layer, and feature code in the “Create Point” section (5A) to your desired settings. Underneath is the “Coordinates” section, which automatically populates but is editable if necessary. Lastly, if feature definitions have been imported, the user is able to map selected attributes to the manhole. With these steps complete, click on “add” at the bottom of the pane to generate the newly extracted manhole feature!
6. For automatic manhole extraction, the workflow now requires user input. This tool was built using a two dimensional deep learning method and therefore extracts anything the model believes might be a manhole.This means that the model is very precise in measuring the center and diameter of every manhole within the dataset. In the “Settings” section, users can move the slider to change the confidence threshold to either include or exclude potential outliers (6A). With this complete, click on the “Extract Manholes” button above the slider and all the manholes in the dataset will be automatically extracted.
7. All of the extracted manholes will be visualized in the plan view, and a new pop up bar will appear. This allows the user to verify each manhole individually as they move one by one in a “traveling salesperson” path. Users can choose to ignore, mark, isolate, extract, and connect each extracted manhole using a polyline (7A). If the user is happy with their result, the workflow returns to the same process as manual extraction. Edit the point settings, coordinates, and attributes for each extracted manhole and then click “Add” at the bottom of the pane.
8. That is it! Using this workflow any user can quickly locate, define, and extract manholes in any aerial or terrestrial point cloud dataset.
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