[mkgmap-dev] Issues with --housenumbers

Thu Jan 8 11:40:18 GMT 2015

gerd
unshure why , but some messages from the list , are hitting my SPAM box ,
even though i say this list is ok

any ideas
stephen

On Thu, Jan 8, 2015 at 9:09 PM, Gerd Petermann <
gpetermann_muenchen at hotmail.com> wrote:

> Hi all,
>
> during the last weeks I tried to improve the --housenumber option.
>
> First of all: In most cases the existing code works quite well,
> but in many special cases it fails.
>
> I did not yet find a good solution, so I start to describe the problems
> with the existing code.
>
> 1) No support for random house numbers.
> In some areas there is no obvious order in house numbers.
> Nevertheless the current code in mkgmap always produces
> house number data that assumes that the numbers are either
> in ascending or descending order. We would need new data
> structures to support this, or at least ignore random housenumbers.
> The effect of the current code is that MapSource shows multiple
> possible places when you enter a road and a housenumber,
> and maybe none of the places is correct.
>
> 2) No plausibility check is done.
> The current code assigns a house (number element) to the closest road
> segment.
> It orders the houses by sorting these closest points.
> a) This doesn't work very well when multiple houses lie at the end of a
> road.
> As an effect, a house with number 12 maybe assigned to the left side of a
> road
> containing only odd numbers (or vice versa), or
> b) It also often fails when multiple houses are connected to the road
> with  an unnamed
> service road. In many areas you have a group with odd numbers 1-9 followed
> by another group
> with numbers 11-17. Depending on the position of the houses, the
> calculated order might be
> 5,7,9,1,17,15,13,11 which results in an interval 5..11 instead of 1..17.
> The result also depends on whether the service road is in the map or not .
> c) In some areas, different road objects are created with the same road
> name, e.g. when
> a p-shaped road is split or the road forms some kind of grid like this a
> #  sign.
> In such an area it is likely that some houses are assigned to the wrong
> (part of a )road.
> d) In some cases we might be able to detect wrong OSM data as such and
> print
> a corresponding message.
>
> Both points 1) and 2) are correlated. Without a plausibilty check we
> cannot detect
> the random house number case, so I think it is an interesting problem
> of pattern recognition. The human brain is very good with that, but it is
> difficult to find
> a quick and good algo for it.
>
> Gerd
>
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>
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