How does the Remove Vegetation tool work?

The Remove Vegetation tool in TerraScan removes points deemed to be in low vegetation from points classified as ground. It functions well within a limited area defined by a MicroStation fence or selected polygon.

Fig. 1: Remove Vegetation settings

The tool works by fitting a plane or multiple planes to the points in the defined area, determining the fit to the plane, and reclassifying any points that fall outside the limit. It works best if you limit the area to not cross other features, such as a road or berm. It can be useful for “cutting” though heavy vegetation around waterways or crop fields. Remove Vegetation can also help one interactively clean low vegetation from hillsides which otherwise cause rough contours on those slopes.

Setting Effect
From Ground  Source class, usually a ground class; only points from the selected class is effected. The list contains the active classes in TerraScan.
To Class Target class into which points are classified. The list contains the active classes in TerraScan.
Only visible points If on, only points that are visible in the fence are effected, even if their display is switched off.
Limit Distance up to which points above a surface defined by the lowest ground points are classified. Given in the master unit of the design file. The amount of effected points is shown next to  the input field.

It’s a good practice to use the Test function to sample and revise your limit setting on a smaller portion of the area you’re trying to correct before attempting to run the tool on a larger fenced area. It will take longer to run on the larger area and will show a “Computing Vegetation Removal” box while processing.

When determining the Limit value, the default is 0.10 (given in the master unit of the design file), and can be adjusted in relation to the level of accuracy you are trying to achieve (1/2 of the contour interval is a good place to start).

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