Filter Points Command

Filters points from the data base by removing points within specified tolerances.

This feature is particularly useful if excessive amounts of points have been collected and the data set is too dense. This is generally a problem when importing DXF or DGN files as common end points of lines are duplicated

The Maintenance/Filter Points command is selected from the Plan View Utilities task.

Filter Points dialog box

Item	Used to
Index Region Size:	Select a region size which will be used in the filtering process to index the data into a number of regions. Selecting an appropriate region size maximises the speed of the filtering process. Typically, a region size between 500 and 1500 points will give the fastest results, but this will depend on the hardware being used and the amount of available memory.
Filter X & Y Tolerance:	Key in the East and North difference tolerance. Points which are within the specified distance of each other in both the East and North directions will be filtered, provided however that they are also within the Z tolerance (if specified). This field must contain a value if Filter X & Y is active.
Filter Z	Specify that points are to be filtered based on their proximity in elevation as well as their X & Y proximity.
Z Tolerance:	Key in the Elevation difference tolerance. Points which are within the specified elevation difference of each other will be filtered, provided however that they are also within the X & Y tolerance. This field must contain a value if Filter Z is active.
OK	Perform the filtering operation. The filtering operation may take a considerable period of time to complete, particularly for large data sets.
Cancel	Close the dialog box without filtering.

During the filtering process, each point in the data base is compared to all other points and those within the tolerances specified are deleted, with the exception of arc and circle points which are treated differently. Arc or circle points can only be filtered if the resulting arc or circle point position does not jeopardise the mathematical integrity of the arc or circle. Therefore points used in arcs or circles may not be filtered unless there are points in the exact same locations as the arc or circle points.
Lines associated with points deleted during the filtering process are automatically amended to the position of the appropriate point remaining in the data base.
The attributes of a point remaining in the data base may be automatically amended during the filtering process to assume certain attributes of deleted points.

The elevation of a deleted point will be transferred to the appropriate remaining point if the remaining point did not initially have an elevation.
If a deleted point is contourable, then the appropriate remaining point also becomes contourable, even though it may initially have been non contourable.