[mkgmap-dev] RFC: naming unnamed roads

Thu Apr 30 15:31:45 BST 2015

Hi all,

thanks for the input.
Please don't mix up the routing part and the address search.
I don't want to discuss here if you are allowed to get to that point,
but yes, I'd prefer that address search returns a point on a public road
if that point is close. 

We recently found out that we can use address search in Garmin software
without even storing any routing information in the map, because all
address information is stored in the NET sub file, while routing requires the NOD
sub file.
The big limit in the Garmin format is that address data is stored with roads.
In other words, the result of Garmins address search is a point next to a road,
and can only be next to a road, this also means that it requires quite a lot 
of bytes to store a single road for each address which would allow 
very precise address search (presuming that the OSM data is precise
and not itself an approximation like the addr:interpolation ways).

I think I have made up my mind now how to handle the special cases.

I think mkgmap should only use the closest road if that is much closer than the road 
with the matching name. 
I have to find out how to calculate what "much closer" is ;-)

Gerd

From: gdt at ir.bbn.com
To: marko.makela at iki.fi
Date: Thu, 30 Apr 2015 09:57:04 -0400
CC: mkgmap-dev at lists.mkgmap.org.uk
Subject: Re: [mkgmap-dev] RFC: naming unnamed roads

Marko Mäkelä <marko.makela at iki.fi> writes:

> The general assumption would seem to be that the street names attached
> to house addresses belong to roads that are reachable by car, or that
> each residence is reachable by car. Maybe in some rare case there is
> some access restriction on the road associated with the address, such
> as access=destination. There could be named cycleways or footways
> between the road and the address node, but no named public roads with
> a different name, unless there is an error in the map data.

That's an interesting point.  In the US, around me, there really aren't
such assumptions.  Instead, a lot (area of land that can be bought and
sold as a unit) has an address, generally taken from a public or private
way that borders the lot.  Some lots don't really have addresses that
are useful, if they aren't near roads.  Then a building on the lot,
certainly if there's only one, inherits the address of the lot.  ANd if
there's going to be a building, then the lot needs to have a proper
address (for emergency services purposes) and one will get assigned.  So
it definitely tends to work out 99.99% of the time that a building's
address is near the named road, and that one drives to that road to
access the building, but it's not strictly by design.  In confusing
cases new addresses tend to get made up, usually by granting the (new)
access road a proper legal name, so it that sense what you said
describes how we do it.    That's a long way of saying that it's messy
and that general rules don't always hold (in mass.us; not saying that
applies to .fi).

This is quite separate from access.  There are addresses on military
cases, and very often in residential complexes with gates that you need
a code/etc. to get through.   So it's not just access=destination but
access=private, and yet they are real addresses on named roads inside
the gate.

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