## Filter Boundary Tool

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hernanitheias@netcabo.pt
MOHID Beginner
Posts: 19
Joined: Thu Jan 01, 1970 00:00

### Filter Boundary Tool

Hello Folks,

A small note about Filter Boundary Tool (in Mohid GIS tool menu).

WHAT IS IT FOR?

Sometimes boundary definition is too refined and you might need to coarsen it in order to generate a mesh or interpolate bathimetry.
Filter Boundary tool is a filter that averages the boundary line. It preforms nothing but a moving average on the line coordinates so small perturbations are eliminated. This average is weighted accordingly to the distances from the central point of the moving average.

HOW TO USE IT?

Select 'Tools->Filter Boundary...'
Now you select the polygon-that is, your boundary-you need to coarsen, give the values for the parameters and then click on 'Add Modified'.
Here, a description of the parameters:

i) Boundary definition (D) : all segments smaller than this length are removed from the polygon.
ii) Average order (N) : perform moving average over the number of points given here. The average distance between N consecutive points should be about D. Bellow a figure that illustrates an average order of 5.
iii) Central weigth (W) : in the average process a higher weight can be given to the central point of the moving average. As a result, he resulting filtered boundary will stick closer to the original contour line. This weight ranges from 0 to 1. If W = 1, the resulting polygon will follow exactly the boundary line. A recommended value is 1 / N.

Any complain on this should be addressed to me.
Now go to work.

CampuzanoFJ
MOHID User
Posts: 46
Joined: Thu Jan 01, 1970 00:00
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