Am 24.01.2011 09:39, schrieb Roger Slevin:
I have not been able to follow the large number of posts on this group in
recent weeks - but I can confirm that stopareas are an important part of
NaPTAN data in the UK, and are an important aspect of the way that stops
data are used in journey planning applications.
This is true, but IMHO obsolete. They are used in situations where the
routing application does not possess the information on the location of
stops. OSM does have that information. Such places can be calculated,
instead of being entered by hand.
It would be a pity if OSM
decided they were not needed ... because they are needed by at least some
USERS of the data.
As far as I understand the issue, stop areas are used to tie different
stops into one "transferring area". This is a common concept, it exists
in both Google Transit and HAFAS. But it could be easily replaced by a
simple calculation of which stops are close enough to be considered "a
pair of stops where the user can transfer". This would have the
advantage over the existing approach by adding the ability to calculate
different costs of transfer - static transfer tables have fixed transfer
costs, often regardless of the distance.
In human language: present routing apps have a fixed table where they
will let you transfer between stops of different names, e.g. to transfer
from "City, Railway Station" bus stop, to the actual railway station. Or
between two bus stops which are common transfer points, but have
different names. Present-day software does allow the calculation of
alternative routes with a walk *to* the first stop and *from* the last
stop, but it have a problem with walk-bus-*walk between any two
stops*-bus-walk solutions. Those are normally (daytime, weekday) not
important, but often critical when bus service is less frequent: night
time, low density areas, etc. If I understand the problem correctly,
such approach comes from the times when routing apps did not have the
geographical location of bus stops, instead they created a virtual mesh,
where transfer nodes had to be defined separately. I understand stop
areas to be those nodes - but we are in 21st century, we have all the
necessary info to calculate what we need, instead of defining it by humans.
The definitions of stopareas need to be created by
those who have a functional need for them
Possibly without the regard of the human of teaching beginners how to do
it.
- they are not arbitrary -
And that's another point against them: how is a transfer place marked by
a user better than a calculated pair of bus stops? Do I really have to
transfer where *you* want me to?
Greetings,
--
Best regards, mit freundlichen Grüssen, meilleurs sentiments, Pozdrowienia,
Michał Borsuk
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