Line Delta Filtering

This reduces detail by assessing the distance between points and removing one or more if the displacement is less than the given threshold. This technique is simple but rather crude, although sufficient in many cases. It fails to take into account the straightness of lines and may remove points without trying to correct other point positions to compensate.

Cannot be used in conjunction with Line Simplification or Angle Change Filtering, but can be used with Island Size Filtering

Parameters:

Line Delta and Delta Sum. Values are entered in Map Units.

Operation

Removes points whose distance from the previous point is less than Line Delta, unless the segment distance between this point and the last not-removed point is greater than Delta Sum in which case the point is kept. The Delta Sum therefore ensures that all points are not removed.

To apply Line Delta Filtering to a Layer:

• Select Layer | Filtering... to bring up the Filtering page
• Select the Line Delta Filter Apply checkbox
• Supply values for Line Delta and Delta Sum using one of the following methods:
• Enter a value directly into the edit box
• Press Evaluate to scan the currently loaded layer and suggest values for Line Delta and Delta Sum. Then press Transfer to transfer the suggested values into the parameter boxes
• Press Suggest to evaluate a value and Transfer it to the parameter box in one operation
• Press OK to accept the changes