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[mkgmap-dev] is_in filter

From Felix Hartmann extremecarver at gmail.com on Wed Feb 8 10:12:23 GMT 2017

On 7 February 2017 at 23:52, Andrzej Popowski <popej at poczta.onet.pl> wrote:

> I like your ideas about is_in and urban areas. But I have doubts about
> practical results. IMO areas like landuse=residential or place=city/town
> aren't mapped well in OSM data. So even if you add some new features to
> mkgmap, it won't be useful, because input data is not precise.
> Some consideration about urban area. I think using buildings or house
> numbers as indication of urban area won't be reliable. Mostly because these
> are data from imports, so some cities get them while others still do
> without. Probably highway's junctions (crossroads) could be the best
> indication of urban area. Roads are usually mapped correctly and number of
> junctions shows complexity of road network.

You have a good point there - I also think residential and city/town are
not that well mapped. Housenumbers are pretty well mapped in many european
countries though - but not in the rest of the world. Buildings I would
guess are sufficiently mapped in most european countries in OSM.
Road junctions have one problem - actually residential areas (as in where
people are living) have most junctions, while city centers / commercial
areas feature much bigger buildings and less intersections.  Maybe the kind
of roads in such areas would help to better identify them. Urban areas
would be easy to find however - take the amount of crossings from
highway=track/path/cycleway vs
highway=residential/primary-secondary-tertiary-unclassified and the picture
should be very clear.

I think both methods will allow for an improvement in routing as well as an
improvement to exclude clutter from buildings in maps if we can derive a
classification level of urbanisation from it and feed it to mkgmap like
bounds and sea files.
My idea would be there should be an analysis of 400x400m patches - then
join them and find out how big the area becomes - any areas that have more
than 3-4 connected patches can then be classified as urban in the
"urban_bounds" file - if it's one or two of such patches - I'ld rather keep
the buildings in my maps and also still consider it rural (because for a
tiny mountain village - I'ld like to keep them - however for a mountain
town like Zermatt, Ischgl or their like - I'ld prefer to remove them -
while for big cities is essential to remove the buildings.

Felix Hartman - Openmtbmap.org & VeloMap.org
Schusterbergweg 32/8
6020 Innsbruck
Austria - Österreich
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