[mkgmap-dev] The 0x4b background polygon in the overview map

Fri Jan 12 13:31:59 GMT 2018

So your idea was basically:

User has splitted a data file covering city A in the upper part and city
B in the lower part. Now user wants to ask mkgmap creating a map with
that data file for city A only by giving mkgmap a polygon only covering
upper part of that data tile.

Ok, I haven't thought about it. So I would agree with you, that both
maps should follow that given poly-file. That would also make handling
of overlapping map areas, which are splitted in one step more easy. But
will require some changes in splitter too. Following the above example,
if I give splitter an osm-file with rectangle of city A and another
rectangle of city B, splitter will create 2 data tiles. In case A and B
are overlapping, 3 tiles will be created. But finally the tiles will be
much better with that additional polygon, as splitter just can use one
big tile instead of 2 or 3 smaller ones. At the moment some tiles of my
maps are pretty small, because of that overlapping areas.

Henning.

On 12.01.2018 20:23, Gerd Petermann wrote:
> Hi Henning,
>
> reg. Bremen:
> I thought the other way around. Say you split and compile Niedersachsen as 15 rectangular tiles.
> Next you compile Bremen using some of these tiles and an polygon for Bremen that is
> only used for the overview map. I guess that would look very strange.
> I also don't know yet if Garmin software complains when an overview map doesn't fully
> cover the tiles.
>
> Gerd
>
> ________________________________________
> Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Henning Scholland <osm at hscholland.de>
> Gesendet: Freitag, 12. Januar 2018 13:16:19
> An: mkgmap-dev at lists.mkgmap.org.uk
> Betreff: Re: [mkgmap-dev] The 0x4b background polygon in the overview map
>
> Hi Gerd,
>
> I probably didn't got your issue.
>
> So far I understand I gave mkgmap a list of data tiles or already
> compiled map tiles. based on this mkgmap creates a complete map. At the
> moment the overview map is rectangle of maxlat,maxlon,minlat,minlon.
> Based on my suggestion user in future would be able to gave a different
> polygon for overview map. If I let mkgmap use the tiles of Bremen, I
> should use a matching bounding polygon. Of course if overview map is
> larger than detailed map, the exceeding area will only have rough
> sea/land area and DEM. In your example, if I use Germany.poly for Bremen
> map, I will see rough DEM of Germany and North Sea and Baltic Sea cost
> line (based on polygon). I wouldn't see an issue unless it's fine for
> Garmin. Are you talking about generating a partial map with
> BaseCamp/MapSource? I haven't checked how Garmin handle overview map in
> that case.
>
> I'm not sure, if Garmin supports smaller/larger overview maps then
> detailed map area is available. That's why I was thinking about if we
> need to gave some limits, like overview map shouldn't be larger than
> actual rectangle or not covering all the detailed map area.
>
> Henning
>
> On 12.01.2018 19:43, Gerd Petermann wrote:
>> Hi Henning,
>>
>> I don't think that we should apply a bounding polygon only to the overview map.
>> If you compile tiles for whole Germany and produce a map for Bremen using
>> some of these tiles and an overview map that was created with a proper polygon
>> I would assume that this looks strange when you zoom in/out.
>>
>> I don't understand what you mean with maximizing/minimizing the polygon.
>> Please explain.
>>
>> Gerd
>>
>> ________________________________________
>> Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Henning Scholland <osm at hscholland.de>
>> Gesendet: Freitag, 12. Januar 2018 12:35:04
>> An: mkgmap-dev at lists.mkgmap.org.uk
>> Betreff: Re: [mkgmap-dev] The 0x4b background polygon in the overview map
>>
>> Hi Gerd,
>>
>> I think this would be best and additionally I would suggest to make the
>> polygon defined by user (as suggested in DEM-poly and precomp-sea
>> thread). As default I would limit overview map to the map tiles. Maybe
>> then we should name the parameter --overview-map-polygon=filename
>>
>> I'm not sure, if the actual rectangle should be maximizing the polygon
>> and the map tile area minimizing it or if Garmin doesn't care at all
>> about it. If no external sea-data is given I would keep map tile area as
>> background polygon. Otherwise it will look strange.
>>
>> Henning
>>
>> On 12.01.2018 19:19, Gerd Petermann wrote:
>>> Hi all,
>>>
>>> up to now mkgmap always creates a rectangular 0x4b polygon for the overview map. I wonder
>>> if I should change that so that the 0x4b polygons of the sub tiles are used.
>>> This seems to be the better way if we start using non-rectangular 0x4b polygons?
>>>
>>> Gerd
>>> _______________________________________________
>>> mkgmap-dev mailing list
>>> mkgmap-dev at lists.mkgmap.org.uk
>>> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
>>>
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