[Talk-GB] 10 fascinating facts about OSM & OSGB
osm at raggedred.net
Thu Apr 18 14:02:46 UTC 2013
On 18/04/13 14:14, Shaun McDonald wrote:
> On 18 Apr 2013, at 13:01, "Dave F." <davefox at madasafish.com> wrote:
>> On 18/04/2013 12:52, Shaun McDonald wrote:
>>> Updates are a lot harder to do as you have to deal with differences
>> When you say differences, do you mean within the tags? Does it need to do that, could it not do a simpler find & replace?
> If someone has modified the item in OSM and in NaPTAN then it needs manual intervention as to which is more correct - the one in OSM or the one in NaPTAN.
There are various errors in NaPTAN data. The data was created by
different means in different local authorities and to varying standards
of quality. The position is not always very accurate, but sometimes the
accompanying information can be poor too. Some data are very good, but
until you survey it you just don't know. As someone who has manually
validated every stop in in a city (~1300) and about a third (~900) of
the stops in a large Unitary Authority I can vouch for the differences
and the wide variation in quality. It became clear that in the city the
quality varied from area to area. I suspect that some areas were
surveyed or recorded or checked more diligently than others possibly
because a more diligent or competent person did the work there.
As with almost all imports or external data sources, they were created
by people. These people were being paid to do a job come rain or shine,
however they felt , whatever their own personal circumstances, all of
which affects the quality of their work. OSM surveys are done because
the surveyor wants to do it and so I think we should accept that
sometimes OSM surveys are better than imports. In the case of NaPTAN
that certainly can be true. That's not to say the external data is
useless - finding every bus stop in a city without a list to work from
would have been hard and easy to miss one.
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