[mkgmap-dev] location-autofill=bounds uses a boundary not surrounding the POI

Tue Aug 14 12:40:54 BST 2012

Hi

> I wonder if we should change the behaviour if no city name is found
> should be changed:
>
> 1. Is it possible to have an empty city name? I think mkgmap users do
> not expect that the nearest algorithm is used if city name could not be
> assigned and location-autofill=nearest is not set. If the city name
> could not be empty we could set a default city name.

I think that the autofill option should be completely separate to the
bounds option. If you want to use the pre-compiled bounds then use the
--bounds option, and to use the autofill feature, use the
--location-autofill option. To get both, give both options.

I don't much like the results of the autofill options from my
experience in the UK at least.  I think it is much better for the city
name to be empty than wrong.

I see two main problems with using nearest city.

1. If the tiles are split so that the correct city node is in another
tile then the nearest town will always be wrong.

2. If there is (for example) a large town and a small village 5 miles
apart then a node 2 miles from the small village will be allocated to
the village, whereas in reallity is much more likely to have an
address in the large town.

> 2. The nearest algorithm uses city POIs only. At the time the algorithm
> was implemented this was a reasonable choice. I would now change that to
> use all POIs so that neighboured POIs with a city information could be
> used to find the city name. In this case an addr:city tag of a
> neighboured POI could also be used to set the city name of surrounding
> POIs without city information. For backward compatibiilty we could add a
> new location-autofill option for this.
>
> What do you think?

Sounds good.

How about creating a fall back boundary file by drawing polygons
around POIS that have the same city, to be used only when the real
boundaries are not complete?

..Steve