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[arne anka]

> If you already have the vector data you doesn't need the bitmap data
> anymore because you can render the displayed map directly from these
> data. That is what navit already does and therefor a combination of
> vector and bitmap data makes no sense. It would make the data redundant
> and more complicated.

it would decrease cpu usage for those areas already in png.
i don't know how exactly navit renders, but i got the impression, reading  
and displaying vector data answers for a good deal of delay.

of course one could take the already rendered map and store it as tiles in  
a cache, with an intelligent caching policy one may be able to limit the  
space necessary.
but then again: how many people need these tiles again? and is the  
rendering really the culprit for the notable delay?

but that's only a theoretical question -- the immense need of space make  
tangogpos more ore less useless for me. i don't like the idea of  
downloading a mass of tiles for  arther limited area.
with navit's maps i get all of europe in less than tangogps needs for the  
greater hamburg area ...