Magellan DirectRoute 3.0 Bedienungsanleitung PDF herunterladen (Seite 93)

Chapter 4. Data Filters

GPSBabel supports data filtering. Data filters are invoked from the command line via the '-x' option. It

should be noted that data filters are invoked in the internal pipeline at the point that corresponds to their po-

sition on the command. This implies that specifying a filter before reading any data ('-x <filter> -f <file>'),

despite being legal, will not have any effect. The advantage is that filters can be used intermittently between

several variations of input and output functions. It should also be noted that filtering data from different

input types can sometimes produce undesirable results due to differences in the native data formats.

Beware that most filters only apply to a certain kind of data. This is usually indicated below by referring

to points, tracks or routes in the first sentence which describes each filter or in the table at gpsbabel.org

[http://www.gpsbabel.org/capabilities.html] .

Include Only Points Inside Polygon (polygon)

The polygon filter includes points if they are inside of a polygon. A polygon file looks like an arc file,

except that the arc it describes must be a closed cycle. That is, for a simple polygon, the first and last points

must be the same. Here's a square:

# A square (not really) polygon

41.0000 -85.0000

41.0000 -86.0000

42.0000 -86.0000

42.0000 -85.0000

41.0000 -85.0000

Polygons may include islands and holes. To include an island or a hole, just append it to the main polygon.

# A square polygon with a triangular hole

41.0000 -85.0000

41.0000 -86.0000

42.0000 -86.0000

42.0000 -85.0000

41.0000 -85.0000

# The hole begins here

41.5000 -85.5000

41.6000 -85.5000

41.6000 -85.6000

41.5000 -85.5000

As with the arc filter, you define a polygon by giving the name of the file that contains it, using the file

option.

Note that this filter currently will not work properly if your polygon contains one or both poles or if it

spans the line of 180 degrees east or west longitude.

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Magellan DirectRoute 3.0 Bedienungsanleitung Seite 93