Low points

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Low points

Low points

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Low points routine classifies single points or groups of points which are lower than other points in the surrounding. It is often used to search for possible error points which are clearly below the ground.

The routine compares the elevation of each point or point group with any other point within a given 2D radius. If the point or point group is clearly lower than any other point, it is classified.

lowPoints_single

Single low point classification

lowPoints_group

Group of low points classification

The routine finds the lowest point or point group in a data set when it runs once. If there are low points on several elevation levels below the ground, it should be executed several times with different settings. Typically, the routine is included in a macro for ground classification in an airborne laser data set and depending on the amount of error points below the ground, there are two or even more steps for low point classification.

lowPoints

SETTING

EFFECT

From class

Source class(es).

To class

Target class.

Search

Defines the target points: Single points or Groups of points.

Max count

Maximum amount of points in a group of low points. This is only active if Search is set to Groups of points.

Inside fence only

If on, points inside a fence or selected polygon(s) are classified.

More than

Minimum height difference between a single point or a group of points and a point in the surrounding. Normally a value between 0.3 - 1.0 m.

Within

Size of the 2D search radius. Normally values between 2.0 - 8.0 m.