This topic reminded me of some thoughts I had about time-based
tagging but did not pursue. I have a professional interest in planned
features but a leisure interest in historic features such as ancient
roads. The OSM database could include both these types of feature but
for general purposes the map should only show what is there now, not
what used to be there but has gone or what may be there in the
future. My thought was that there could be a time-based tag which
would show the time-span of a feature. It might be called 'epoch='
and could indicate when a feature existed/will exist. Anything with
an epoch which did not include today would not appear as standard,
but a time-based viewer might allow users to 'scroll through time'
seeing features appear/disappear as the viewer's epoch entered/left
that of the features.
A difficulty is that there will usually be some uncertainty about the
dates, so the tag grammar would need to take account of this.
Sometimes the beginning or the end date will be unknown or there will
be only the most approximate knowledge of a date, so the tag grammar
must allow for various levels of accuracy and for incomplete epochs.
One approach might be to use a grammar like from>to so a road due to
open in December this year could be tagged epoch=12/2008> or an
ancient track that fell out of use and disappeared in the 16th
century might be tagged epoch=>C16. A feature that was known to exist
for much of the 1700s but probably not before or after could be
tagged epoch=C18 (implying from/to dates of 1700 and 1799) whereas a
temporary path existing just for the duration of a construction
project might be tagged epoch=12/03/2006>23/12/2006.
Features with no epoch tag (like pretty much everything in the map
now) would default to 'now' and if the viewer left the present epoch
to look back at past features or forward to planned features would
show these against a dimmed backdrop of the present-day map. Such a
viewer could use the standard bitmap tiles for the present-day
background but would need to use vector data from the database for
past/future features.
elvin
From: "Andy Robinson \(blackadder-lists\)" <[EMAIL PROTECTED]>
Date: 4 June 2008 08:54:53 BDT
To: <[email protected]>
Subject: [OSM-talk] Enabling communities to use OSM as a planning tool
Lat night I attended a steering group meeting for my local Connect2
[1]
project in north east Birmingham [2]. One of the things that the
group could
benefit from is rapid response on mapping so that it can discuss route
options for the new cycle/walk routes to be built under the
project. OSM is
the logical tool to use for this process and I'm keen to show what
we can do
with the OSM data and the OSM platform to support the work. At the
moment
everything is done as overlays on Ordnance Survey 1:10,000 mapping,
not an
ideal way to integrate ideas into the existing infrastructure.
This brings me to the point though. Currently we map physical
features as
they exist and in some cases the alignment of known construction,
what we do
not do is use OSM as a planning tool. What are people's views on
this? It
seems that OSM is an ideal platform for enabling communities to
develop
their own planning, without having to rely wholly on the GIS
department of
their Local Authority, it also makes publishing ideas so much
easier without
the encumberment of the OS licence restrictions.
Anyway I'm going to give it a try here and come up with some
logical tags so
that the data does not get rendered by default unless a custom
style sheet
is deployed. But maybe the easiest was is to have the renders
ignore data
that carries a specific tag. planning= perhaps?
I'd welcome some feedback.
Cheers
Andy
[1] www.connect2.org.uk
[2] www.connect2birmingham.org
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