On 05.05.2011 23:01, WanMil wrote:
>>> The locator branch is in an early alpha status. Such small
>>> optimizations can be added later on when the main problems are solved.
>>>
>> Do you consider this as small optimization?
>
> Yes. If you have other numbers please post them.
>
> As long as splitter/mkgmap handles rect tiles only and not polygon
> shaped tiles it won't help (for most cases) to define a region which
> is assigned to all objects. So you save the country assignment only.
>
> And the processing time for this is neglegable compared to the other
> assignements of region and city.
> The reasons for this are very easy.
> 1. Counts
> A common tile contains data of a bit more than one country on average.
> But it contains up to some 1000 boundaries of other admin levels.
> So you have a lot of more queries to do for non country information.
>
> 2. Size of countries
> Most rectangular tiles cover one country only. Using the precompiled
> boundaries of the locator branch you get exactly one rectangular
> polygon for the single country and that's very low cost for retrieving
> all containing elements: it's just all.
>
>>
>> I think most people use / create maps from country extracts by geofabrik
>> anyhow, so this is the first important step and save a lot of processing
>> time / maybe even be enough for many people to find street addresses.
>
> Solve the main problems first (what to do with streets crossing from
> one city to another - cut them?, find a fast rtree like structure to
> perform the queries etc.)
> Then you can start to measure the performance and to think about
> optimizations. At least you can think about fine optimizations. And
> then you need someone who implements them: kind inviation for you to
> do so.
>
> WanMil
okay, thanks for the clarification, I thought the country selection
takes more.
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