On 31 Mar 2009, at 13:23, Andy Robinson (blackadder-lists) wrote:
I've already started correcting data like this. I too have noted
that some
stops are not correctly positioned in relation to the road they are
on.
Where we only have a single trace along a road they could be correct
but the
ones I looked at last night where we have plenty of traces (main
road) were
in some cases either too far back or too close to the centreline of
the
road. I also fond some possible referencing errors for bus stop
pairs on
either side of the road but need to resurvey as a double check.
As of my mapping session this morning I'm taking my bike right up to
the
stop and taking the photo from directly under the sign. That should
help see
what sort of positional errors exist in the data. The only problem
is that
I'm mapping Walsall and so need more imported data before I'll
know ;-)
Import looks good. A few points:
1) The bearing is useful to ensure that the stop is put on the correct
side of the street) . Normally the stop will already be on the correct
side using the lat-long, but if the stop in misplaced by poor GPS then
we could place it on the wrong side. I did find one that was on the
wrong side of the street in the OSM environment using the bearing from
the official data.
2) Some Naptan records seem to be missing in OSM. In the case where
there is already a bus stop in the right place is the Naptan record
just being deleted in the review pass? If so then important data for
maintenance is being lost. I would suggest that the two records are
merged to ensure that there are NaPTAN codes for every stop.
3) I find it interesting that in some places OSM has bus stops that
are not in NaPTAN, that might be because they have been removed
recently or be an omission in NaPTAN.
4) I notice that sometimes the NaPTAN stop and the OSM one are some
significant distance apart which begs the question about which one is
right.
Anyway, it looks like the detective work is now starts! Great work.
Regards,
Cheers
Andy
-Original Message-
From: talk-gb-westmidlands-boun...@openstreetmap.org [mailto:talk-gb-
westmidlands-boun...@openstreetmap.org] On Behalf Of Brian Prangle
Sent: 31 March 2009 9:46 AM
To: talk-gb-westmidla...@openstreetmap.org; talk-transit@openstreetmap.org
;
Thomas Wood
Subject: [Talk-gb-westmidlands] Naptan alignment
Thomas
I've also looked at Google maps and their alignment is off too in
exactly
the same way ours is in areas I know well and have surveyed, so I
guess
it's down to the NaPTAN data. There are examples where I know the
bus stops
are in a row along the street (Corporation Street and Acocks Green
Village
for example) but NapTAN has one or two skewed from the line by
several
metres. Currently I favour correcting the NapTAN data to what we
know on
the ground, but until a consensus emerges I'm laying off the urge to
correct it.
Regards
Brian
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