On 11/03/11 10:19, Steve Chilton wrote:
I have been asked by editor of the Cartographic Journal to write a short piece
on the effect of the release of OS OpenData on the OpenStreetMap project, and I
am just trying to gather my thoughts, and make sure I cover all bases.
I was present at Blackadder's Society of Cartographers talk on "Why OSM won't be
bulk importing OS OpenData" and am aware of the work Chris Hill has done on admin
boundaries etc.
Obviously also aware of the ITO work with OS Locator and what people have done
with that.
There was work on importing detailed water features, was that Chris as well
(goes off to read back through his blog).
Can anyone point me to others who have explored the possibilities that OS
OpenData provided - PARTICULARLY if they can evidence WHY it is NOT of value to
OSM?
OS Opendata gives us access to places we can't otherwise go, such as
docks, but so does aerial photography. It provides features such as
power lines and some water ways that cross land that we don't have
access to. It gives us access to the official, up-to-date boundary data
that is just not available in any other form that we can use. It is much
more up-to-date than some of the aerials and some of the various forms
of data have names on them (Streetview and Locator) though that does
have some small level of errors. There is also the postcode dataset
which is a valuable source of data that would be very difficult to
gather exhaustively otherwise.
On the down side the level of detail is low. The building outlines,
especially houses, are clearly crude and only indicative. I have been
adding buildings and, combined with a survey, addresses and it is useful
to use OS Streetview where the aerials are too old to see recent
developments or occasionally where buildings are hidden by tree cover,
but generally Streetview is not as good as aerials, which themselves are
not that detailed in some areas I'm interested in. The VectorMap is
(counter to its title) really taken from a render layer. Waterways have
annoying gaps where anything crosses them. Woods have somewhat chunky
outlines and annoying gaps. StreetView has hints of tracks where the
names remain but the track detail has been removed.
The alignment of Streetview (against multiple GPS traces) is
consistently off in the areas I've used, but that could be the way
someone in OSM has used it. Aerials are also off, but not as
consistently, which means always checking the alignment before use.
Some of the datasets are more useful than others. BoundaryLine is very
useful, VectorMap District Settlements by area seem to me to be total
rubbish - horribly crude, undefined as to what they show and badly
out-of-date.
I think OS Opendata has been useful, but it has also attracted the
armchair tracer. Much of North and North East Lincolnshire is only in
OSM because it has been traced from OS OpenData. All of the detail from
a ground survey is missing, yet the map looks quite complete at first
glance. According to Jerry's blog (
http://sk53-osm.blogspot.com/2011/02/updating-pub-density.html ) Grimsby
has no pubs, this because Grimsby has been traced not surveyed. OS
OpenData made this possible but it is not directly responsible.
--
Cheers, Chris
user: chillly
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