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TerraScan User Guide

Navigation: Tool Reference > TerraScan Window > Tools pulldown menu

Smoothen points

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Smoothen points

Smoothen points command can be used to smooth attributes of laser points. The points are modified according to their closest neighbours. This results in a more homogeneous appearance of the point cloud. The following methods can be applied:

Xyz - 3D smoothing process, 25-30 neighboring points are used to fit a 2nd degree surface, points are moved in XYZ closer to this fitted surface, points on vertical surfaces are smoothed in XY direction, point on horizontal surfaces in Z direction.

Elevation - adjusts elevation values of laser points iteratively. A best fit plane equation is derived for this group of points and the elevation of the center point is adjusted to better match the plane equation. Then, the application tries to decide what areas became smooth and what areas did not result in a smooth surface. Only the smooth areas are finally adjusted. Areas which still have significant elevation variation are restored to the original state.

Intensity - averages intensity values of each point with its closest neighbors.

Color - averages color values of each point with its closest neighbors.

Distance - averages distance value of each point with a given amount of neighbor points. This may be useful to reduce the noise of vegetation index values derived from color information. Thus, the result represents more the real vegetation pattern of an area with less noise. This may also improve the classification of ground in photogrammetric point clouds, as it can be supported by the distance value.

You would normally run elevation smoothing on ground point class in order to:

remove random variation in laser point elevations and produce a more accurate model.

produce a smoother surface so that contours look nicer.

produce a smoother surface so that profile drawings look nicer.

You should not use elevation smoothing if:

the terrain is covered with low vegetation and there are no smooth surfaces.

you intend to extract features which have only a small elevation change such as road curb stone lines. Those would be completely smoothed out.

You can include a point class into the smoothing process which is used in the smoothing process but not modified. You can use this capability, for example, if you have classified points close to breakline features into a separate class (elevation smoothing) or if points on paint markings are classified into a separate class (intensity smoothing for points on road surfaces).

To smoothen points:

1. Select Smoothen points command from the Tools pulldown menu.

This opens the Smoothen Points dialog:

smoothen_points

smoothen_points_intensity

smoothen_points_color

2. Define values and click OK.

This starts smoothing process.

SETTING

EFFECT

Smoothen

Smoothing method: Xyz, Elevation, Intensity, or Color values.

Modify class

Point class(es) included in and modified by the smoothing process.

_select_classes

Opens the Select classes dialog which contains the list of active classes in TerraScan. You can select multiple source classes from the list that are then used in the Modify class field.

Fixed class

Point class(es) included in the smoothing process but points in these classes are not modified.

_select_classes

Opens the Select classes dialog which contains the list of active classes in TerraScan. You can select multiple source classes from the list that are then used in the Fixed class field.

Max fix | up | down

Maximum horizontal/vertical up/down change to apply to a point. This is only active if Smoothen is set to Xyz or Elevation.

Use reliability as weight factor

If on, the reliability value stored for points is considered when smoothing points. This is only active if Smoothen is set to Xyz.

Radius

3D distance from a point which defines the sample area from which the average intensity or distance values is derived. This is only active if Smoothen is set to Intensity or Distance.

Limit

Defines the maximum intensity value of points that are effected by the smoothing process. Given as factor of the standard deviation of intensity values in the sample area defined by the Radius. If a point differs more in intensity from its neighbours than the computed limit, it is not effected by the smoothing process.

This is only active if Smoothen is set to Intensity.

Average max

Maximum amount of points that are included in the average distance computation. This is only active if Smoothen is set to Distance.

Modify hue

If on, the hue component of the HSV value of a point is modified. This is only active if Smoothen is set to Color.

Modify saturation

If on, the saturation component of the HSV value of a point is modified. This is only active if Smoothen is set to Color.

Modify value

If on, the value component of the HSV value of a point is modified. This is only active if Smoothen is set to Color.

Inside fence only

If on, only points inside a fence or selected polygon are effected by the process. Requires a fence or a selected polygon in the CAD file.

TerraScan User Guide   26.07.2021   © 2021 Terrasolid Ltd