[OSM-talk] Micromapping [was RFC: Scout Camp]
Robert (Jamie) Munro
rjmunro at arjam.net
Tue Jun 12 12:01:03 BST 2007
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Mike Collinson wrote:
> There is an interesting general issue partially raised here.
> We are currently missing tags and possibly structure to deal
> with "micromapping" - mapping of facilities and features at
> high zoom levels, broadly in the 1:1,000 to 1:5,000 range of
> traditional printed maps.
> OSM was originally envisioned to be just that, a street map.
> This implicitly assumes a base map at around 1:10,000 -
> 1:25,0000 and then zooming out by selectively dropping features.
> Micromapping needs its own support and probably debate on
> whether it should be supported in OSM at all. I certainly think
> it should. The opportunity for the general public, NGOs and
> other organisations to create highly detailed maps of local
> communities and facilities such as camps, sports, theme parks,
> resorts, shopping centres ( ... ) and offer them in a global
> framework to all is just too good to miss. But there are
> questions to be looked at.
> One issue that has risen in the past is implicit scale - a gate
> is dot / node on today's OSM map but may need to be a line/way
> on a micromap.
At micromapping scales, nearly all of our features don't exist. E.g. a
road is no longer simply "a road", it's an area of tarmac, with areas of
pavement (sidewalk) on either side. Buildings like pubs become areas. At
the most extreme, even a postbox or a lamp-post becomes an area feature.
Basically the whole map becomes lines separating area features, rather
than lines representing features. I think this requires an entirely
different data structure, where the areas between lines are tagged, not
the lines themselves. I guess we already have similar problems with
large features like borders between counties / countries / postcodes
etc. The lines themselves are meaningless - it's the things either side
that are the data. We can't use clockwise / anti-clockwise to signal
which area is which because where 3 meet, at least one of the three
needs to point in the wrong direction.
It may be possible to convert micro-maps to lower-detail street maps
automatically, but I don't think it's useful to keep them both in the
Robert (Jamie) Munro
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