[OSM-talk] The Fourth Dimension (temporary mapping)
frederik at remote.org
Tue Jul 24 12:54:38 BST 2007
reading about the floods in England prompted me to think about
whether we should make efforts to somehow include "temporary mapping"
There are many aspects of maps that change "temporarily". Some roads
are closed in winter, but they are not closed at a certain date -
they are closed "in wintry conditions". Some roads are closed long-
term (construction, bridge or tunnel refurbishing), some short-term
(cleanup after accident). Lakes dry up, and flooding creates "lakes"
where there should be villages.
Some of these changes are fixed in start and end date; some just
happen, and are gone after a certain time.
Now we can of course make "mashups" of any kind - "pins on maps"
being the most primitive, or the better way that OJW recently
presented where you can draw on top of maps, or other things maybe.
However, all these are based on having a fixed, raster data base map
and somehow marking stuff on top of that. Which is way inferior to
drawing proper maps from vector data.
If we are to enter time-limited data int our database, this will have
a lot of consequences. For example, we will need at least two types
of rendered maps - one "classic" map showing the "normative" state of
things, how things "usually are", maps that you would use as base
maps for drawing on. And another one showing the "current" state of
things, with lakes removed when dry, villages submerged, roads closed
and so on.
We also need to find proper tags or change the API to model these
things. We could just set "valid-from" and "valid-to" tags and have
renderers etc. deal with it, but (thinking that we might some day
also have ancient roman roads and stuff) it may be an option have a
query whereby you can say "give me this bounding box but only stuff
that's valid for August 2007" or so.
I don't think that our existing history mechanism is sufficient - I
can access the status quo for a certain date in the past, but there's
no way to enter information like "this road will be closed on 29th
July and subsequently demolished" (I'd either have to set up a cron
job or put a "note" in hoping that someone who sees the road after
29th July will then delete it.)
All this is not urgent stuff we need to solve but interesting to
think about. - Maybe historic and future data as well as short-term
changes are not even "our business" and we'd rather count on someone
else to use our data and modify it according to current developments.
Frederik Ramm ## eMail frederik at remote.org ## N49°00.09' E008°23.33'
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