[mkgmap-dev] overview2 branch -- sea not rendered at resolution 12

Wed May 8 16:35:33 BST 2013

Hi Felix,

quite a few numbers, I am not srure how to handle your results.
The current processing in mkgmap is this:
the min-size-polygon value is multiplied by 2 ^(24-resolution), e.g. a value
of 8 will give 32 on resolution 22. This value is compared with the width
and height of the polygon in map units. If both values are smaller, the
object is dropped. 
I am not sure why one wants a rather large value, I guess it makes the img
size smaller. The default
value is 8. 
A possible solution could be to skip this filter for all polygons created by
the SeaGenerator. 

Gerd

Felix Hartmann-2 wrote
> No, they are already missing.
> ---Changing --min-size-polygon=12 to --min-size-polygon=1 and they 
> appear. I think the problem is the size of the sea tiles as they are cut 
> down into smaller polygons by mkgmap itself - because in the input data 
> they are big enough... However therefore I tried around all min-sizes 
> regarding the resolution to see what works!
> 
> So here is a list of the biggest min-size-polygon usable currently:
> 1=good for resolution 10...
> 2=good for resolution 11, variable output on resolution 10
> 3=good for resolution 12, variable output on resolution 11
> 4=good for resolution 12, nearly no output on resolution 11
> 5=good for resolution 13, variable output on resolution 12, no more 
> output on resolution 11.
> 6=good for resolution 13, variable output on resolution 12
> 7=good for resolution 13, variable output on resolution 12
> 8=good for resolution 13, nearly no output on resolution 12
> 9=good for resolution 14, variable output on resolution 13
> 10=good for resolution 14, variable output on resolution 13
> 11=good for resolution 14, variable output on resolution 13, no more 
> output on resolution 12..
> 12=good for resolution 14, variable output on resolution 13, no more 
> output on resolution 12..
> 
> 
> The strange thing about this is, that the sea in the input data is large 
> enough - I think the problem happens when splitting for subdivisions...
> 
> Overview2 branch - before multiple level overview map -- 
> min-size-polygon=12 was fine. GpsMapedit says the resolution is 13. I 
> assume the min-size was not respected because the input data just got 
> carried forward from the last level in the maps - (and 
> --min-size-polygon=12 worked fine for resolution 14!)?
> In that case mkgmap overview2 should take the following min-sizes - no 
> matter what is actually defined:
> 
> max min-size by resolution:
> 1- resolution 10 or lower (10 is working still in Mapsource, dunno about 
> 9 or lower - I think not)
> 2- resolution 11
> 3- resolution 12
> 6- resolution 13
> 12- resolution 14
> 24- resolution 15
> 48- resolution 16
> 96- resolution 17
> 192-resolution 18
> ..... don't think anything that high makes sense, but better continue 
> upwards so it causes no problems. As the results are not really 
> consistent - I would rather take 3 for resolution 12, and not 4 - as 
> maybe closer/further away from the equator results may differ a bit!
> Theese values above, are definitely safe - I never saw missing see 
> anywhere worldwide while using- min-size-polygon=12 at resolution 14...
> 
> 
> 
> On 08.05.2013 07:51, GerdP wrote:
>> Hi Felix,
>>
>> do you see the see in the ovm_*.img files? If yes, the problem is in the
>> part that reads back these files.
>>
>> Gerd
>>
>>
>> Felix Hartmann-2 wrote
>>> On 08.05.2013 02:15, Gerd Petermann wrote:
>>>> Hi all,
>>>>
>>>>> Well, I first thought it would be a Mapsource/Basecamp bug, but
>>>> actually
>>>>> mkgmap overview2 is not rendering the sea tiles down to resolution 12.
>>>>> The lowest resolution working is resolution 14... -- at 13 some sea is
>>>>> rendered, at 12 no sea at all is rendered. I think unlike in my
>>>>> earlier
>>>>> reply to Henning - that this is some internal bug (maybe related to
>>>> that
>>>>> before 13 was the resolution of the overview map)
>>>> I assume the polygons generated by SeaGenerator are too small, means,
>>>> they are all filtered
>>>> in the low resolution levels. Maybe we can implement a merge-polygons
>>>> function to solve this
>>>> problem. Anyway, this is probably not directly related to the overview
>>>> stuff.
>>> that's what I first thought too. But then I looked at a map created with
>>> the same settings using the old overview2 branch (before multiple
>>> levels) - which was done at resolution 13. And there no sea at all was
>>> missing - while now at 13 it is mostly gone. So I guessed that there
>>> must be some other problem...
>>>>> Else I really think that the branch can be merged. It is really
>>>>> working
>>>>> well now... - and I played around a lot with it.
>>>> :-)
>>>> Please post a diff for the default style (or a zip file containing all
>>>> files). I do not fully
>>>> understand the changes.
>>>>
>>>>> Only other thing is maybe to have an option to delete / not delete the
>>>>> ovm*.img files after creation.
>>>> Yes, I think an option is ok. I prefer to have the files as it helps
>>>> debugging.
>>>>
>>>>> Resolution 12 is great for continent maps like Europe (not fully
>>>>> needed
>>>>> - 14 could do), or Asia (13 is a must, 12 would be much better).
>>>> Please place that knowledge as a comment in the style options file.
>>>> Maybe you can also add something to the doc files?
>>>>
>>>> Gerd
>>>>
>>>>
>>>>
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>>
>>
>>
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