[mkgmap-dev] small issue with Way.getCofG()

Sun Jan 4 10:06:55 GMT 2015

Hi Steve,

Steve Ratcliffe wrote
> On 03/01/15 08:15, Gerd Petermann wrote:
>> @Steve:
>> The routine was initially created for the --check-roundabouts option.
>>
>> Later it was also used for --add-pois-to-areas and the --housenumbers
>> option.
>> I got the impression that it might be better to calculate the center
>> of the way bbox for those two, I am not so sure about the roundabout
>> code.
>> What do you think?
> 
> Seems like the current method would tend to place the point near the
> most complex part of the boundary.  This may not be bad, I would have
> to see lots of real examples to be sure.

Yes, correct. I compared these three algos:
1) the existing
2) my patched one
3) center of bbox
For complex shapes (many points), 1) and 2) produce almost equal
results, and in fact the point was more often within the shape.
For simple polygons like small parks, buildings, etc. 1) is worst,
2) is better and 3) is best.

My conclusion: the patch is a simple and good improvement,
for housenumber location calculation maybe it would be better to use
algo 3).

Steve Ratcliffe wrote
> Anyway there are no easy (or even any difficult!) methods that work in
> all cases, so I would just keep it as it is and perhaps should the 
> calculated point be outside the box, move it to the closest point
> inside.

I already looked at the link provided by Andrzej. 
If I got that right, we have two different problems regarding 
the generated POI:
We calculate it once for the whole polygon, before clipping
it to the bbox of the tile, and it might be outside of the polygon
as well as outside of the bbox.

This brought me back to the non-rectangular tile problem and I stop
searching for a solution for the POI problem.

Reg. non-rectangular tiles: I fear we can't use any of the existing
algos in mkgmap to implement this, I'll report details in a different post.

Gerd

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