[Talk-transit] Naptan import

Roger Slevin roger at slevin.plus.com
Mon Jul 27 22:08:12 BST 2009

You ask about the omissions from NPTG.  Perhaps it would be helpful if I described the history of creating NPTG and what the brief has been to local data editors in terms of what is or is not included in the database.

NPTG started life as a national statistical gazetteer based on a collation of different statistical areas (parishes, journey to work areas, towns, cities, etc).  A number of unwanted types of entity in that source data were marked as inactive (things like area parishes which cover several villages) - and local editors were briefed to remove other sources of duplication.

We then had the difficulty of determining what is, and what is not, a locality.  The guidance we have given has been that a locality is a place which locals would consider they lived in, worked in, were educated in etc ... and/or to which highway engineers would consider it appropriate to show on road direction signs.  Although NPTG was originally for public transport purposes, we stressed at all times that a locality should be listed even if it has no public transport - but we know that some local editors have probably erred towards marking some unserved rural hamlets as "inactive". 

All "inactive" localities should still be in the data - so hamlets which are missing may be in NPTG, but marked as "inactive".  However they may simply never have been in the source data - and no one to date has recognised the need to add them to NPTG.  It would be interesting to see what localities OSM holds in its data which are not included in NPTG (as well as the reverse of this) if that is possible.

I hope this helps your understanding of the background.


-----Original Message-----
From: talk-transit-bounces at openstreetmap.org [mailto:talk-transit-bounces at openstreetmap.org] On Behalf Of Christoph Böhme
Sent: 27 July 2009 21:50
To: Peter Miller
Cc: talk-transit at openstreetmap.org
Subject: Re: [Talk-transit] Naptan import

Good evening,

Peter Miller <peter.miller at itoworld.com> schrieb:
> On 26 Jul 2009, at 22:14, Christoph Böhme wrote:
> > I also created a copy of the NOVAM viewer and changed it to display
> > NTPG data instead of bus stops:
> >
> > http://www.mappa-mercia.org/cgi-bin/nptg.wsgi/viewer.html
> Great stuff, and clearly there are many additional place-names in
> NPTG that are not in OSM a present in many parts of the county. I
> checked North Norfolk and bits of Scotland and there are a good
> number of additional places.

I have now also added all nodes with place=* tags from OSM. The NPTG
import will really add a lot of additional places! OSM has only 25397
places in the UK at the moment. However, I was a bit suprised to see
some hamlets in the OSM data which are not in the NPTG data. Do you
know of any gaps in the NPTG data?

> The LocalityClassification field should be more useful and should  
> contain city, town, village, hamlet, suburb, urbancentre, place of  
> interest, other, or unrecorded. I am not sure how well this field is  
> populated - possibly it is not well populated at all. UrbanCentre
> can possibly be ignored.  

The LocalityClassification tag is used 856 times in the dataset. That is
about 2% of all localities.

> The field may be well populated in some parts of the country and not
> in other. I am not sure how much NPTG is used for Points of Interest.
> There is a POI model in NPTG but possibly we treat this separately or
> not at all or import the data as invisible to start with. My main
> interest is the locality names and the main technical job will
> probably be to spot duplicates with what is in OSM already.

Finding duplicates should not be too difficult. We basically just need
to check for each imported location if there are any places with the
same name within a reasonable distance. Except for typos and different
spellings that should work very well. The positions of locations in
both datasets also match nicely which should make it even easier to
find duplicates.

> Would it be worth creating a NPTG Import wiki page and an NPTG
> Import user to do the actual import - ie, keep the documentation and
> audit trail for the two imports separate?

I am in favour of keeping them separate. Both datasets are fairly
independent and we will probably use different methods to import them.
Having everything on one wiki page will be confusing to users, who might
be interested only in one of the imports.


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