### Filtering at map levels

The general representation that is built up in the mkgmap.general package is at the full level of detail that is available in the OSM file. The map however is in different layers at different levels of detail. There are also limitations of the format or the devices that need to be taken care of.

So when we are building up the garmin layers, we send the general representation through a series of filters to fix things up before being placed into a layer. This can involve spliting up lines and shapes, removing points from lines to produce a lower resolution versions and droping elements altogether.