[OSM-talk] OSM maps of Denmark for download to Garmin devices

[Lambertus]

Maarten Deen wrote:
> Lambertus wrote:
>> Maarten Deen wrote:
>>> Not to diminish your work on that front, but I find the tilelayout on 
>>> your site very strange. Of course it is a work of the splitter, but I 
>>> would opt for a manual layout, guided by an initial automated process.
>>>
>> Please forgive me for relying on the automated Splitter layout 
>> mechanism as I have no intention to manually divide the world into 500 
>> tiles (317 America + 182 Europe/Asia/Africa/Oceania currently). 
>> Optimizing the tiles would result in even more, so you'd be talking 
>> about e.g 750 tiles.
> 
> I'm certainly not complaining about your work. It's the reason why I 
> bought a Garmin Nüvi and not a TomTom.
> 
See Garmin...this is why you need to publicize your map format :-)

>> Needless to say: patches welcome ofcourse. The definition files for 
>> Splitter are:
>> - http://planetosm.oxilion.nl/~lambertus/america.list
>> - http://planetosm.oxilion.nl/~lambertus/eurasia.list
>>
>>> IMHO the strategy that the Mapsource tiles use is much more logical. 
>>> Take one big tile, if that has too many nodes, split it in half 
>>> horizontally, if that has too many nodes split it in half 
>>> vertically... repeat until you have a sufficient small amount of nodes.
>>>
>> This strategy is afaik exactly what Splitter does.
> 
> Then it does it in a strange way. I'm sure you've noticed that the edges 
> of the tiles don't line up by just a few 1/100th of a degree in a lot of 
> places. That is inconsistent with a strategy of dividing a tile in half 
> if it has too many nodes.
> E.g. tiles 63240113 and 63240116. One has a north border of 51.679688, 
> the other  51.635742. And then two tiles further east, 63240120 has a 
> north border of 52.679688 again.
> 
Well, maybe not exactly in half, but the idea is the same. Afaik, the 
reason why Splitter doesn't split exactly in half is that there is less 
chance that a polygon is present in too many tiles.

> BTW: have you seen that Mapsource draws the maps as overlapping? I've 
> attached a screenshot of how Mapsource displays maps 63240105 (yellow), 
> 63240175 (blue, continuing to the top) and 63240179 (green).
> They all overlap eachother. According to their definitions, they should 
> not overlap, but mapsource apparently disagrees.
> Any idea why that is?
> 
I've seen this with topo maps made with older versions of Mkgmap as 
well. This might be a bug in Mkgmap or a misunderstanding of the Garmin 
map format but I don't think it's harmful though.