[OHM] Historical Helsinki map published

[SK53]

Hi Chris,

I would encourage you to add it to OHM rather than OSM.

You could use the "City Stripping" technique: take the current road layout
of Helsinki & progressively remove roads which are newer than your target
date. I learnt last week that Prof. Richard Rodger's group at Edinburgh
have done this with their MESH
<http://gtr.rcuk.ac.uk/project/8A5E20E4-ACD2-4248-97A0-5D6F10AA74FC>project,
for at least 7 snapshots of the city's history. (They also make extensive
use of current geocoders largely because Edinburgh addresses have been
remarkably constant over the past 200 or so years; the ability to geocode
historical data such as street directories is a use case which had passed
me by).

The idea of "City Stripping" is that one is correcting for artefacts of the
rectification and of the original printed map by using a more accurate
alignment. Of course changes still need to be made where the current roads
have been realigned.

If creating a snapshot my current approach is to tag *ALL *tagged elements
with a start_date and end_date which adequately cover the period to which
the source map refers. With multiple snapshots the choice of end_date will
be affected by the dates of the next newer snapshot.

I was going to do this with Tartu, but at present
<http://www.openhistoricalmap.org/go/0w8AFiU1-?layers=H&relation=2153396>
this has been entirely re-done manually (the level of detail in OSM for
Tartu was a bit too much to pare down to what I wanted quickly).

It is clear we need some moderate to large scale examples within OHM to
both establish ways of doing things and have something concrete to show
others.

Jerry


On 28 June 2014 20:59, Chris Helenius <chris.helenius at gmail.com> wrote:

> The National Archives of Finland just published a map, from 1823, with the
> old winding streets of Helsinki, overlayed on the then-planned and now
> current street grid. http://digi.narc.fi/digi/slistaus.ka?ay=222866
>
> Here is my rectification which can be used in JOSM:
> http://mapwarper.net/maps/3371#Preview_Map_tab
>
> It most likely displays the largest extent of the historical Helsinki at
> its current position, before the straightening of the roads.
>
> It doesn't display all of the buildings, mostly plots on the centre area
> and some outlying buildings at the wharf in south.
>
> Mapping the historical city has been a desire of mine for several years,
> but is it OK to just map currently nonexistent features on an already very
> crowded district?
>
> Wouldn't that make the map view, when editing and downloading data, even
> more messy?
>
> It also raises the question of correct tags. Should they be
> was:landuse=residential; end_date:1823?
>
> /Chris Helenius
>
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