Increase download limit near the poles?

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Increase download limit near the poles?

Petter Reinholdtsen

When trying to download a reasonable area in Northern Norway, I am
told that it is too large (>0.25).  I assume this is a good value in
England, but closer to the poles it become ridiculously small.  I draw
maps around 69 degrees north.  Can it be made to scale with the
position on the globe?

Happy hacking,
--
Petter Reinholdtsen


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Re: Increase download limit near the poles?

Tom Hughes-3
In message <[hidden email]>
          Petter Reinholdtsen <[hidden email]> wrote:

> When trying to download a reasonable area in Northern Norway, I am
> told that it is too large (>0.25).  I assume this is a good value in
> England, but closer to the poles it become ridiculously small.  I draw
> maps around 69 degrees north.  Can it be made to scale with the
> position on the globe?

Well if you can come up with a good algorithm then maybe we can
consider it ;-) For what it's worth the current test is:

  (max_lat - min_lat) * (max_lon - min_lon) < 0.25

Tom

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Tom Hughes ([hidden email])
http://www.compton.nu/

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Re: Increase download limit near the poles?

Petter Reinholdtsen

[Tom Hughes]
> Well if you can come up with a good algorithm then maybe we can
> consider it ;-) For what it's worth the current test is:
>
>   (max_lat - min_lat) * (max_lon - min_lon) < 0.25

What about something like this:

    (max_lat - min_lat) * (max_lon - min_lon) <
        0.1 + 0.2*sin( | max_lat - min_lat | )

The 0.1 is the minimum value used on equator, and 0.2 is a scaling
factor that is zero on equator and 0.2 on the poles, so in this case
it would scale between 0.1 and 0.3 from equator to the poles.  I'm not
sure if 0.1 and 0.2 are the best values to use, but the structure of
the formula should be clear.  I assume we want to tune it based on
what make most sense around the globe.

Happy hacking,
--
Petter Reinholdtsen


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Re: Increase download limit near the poles?

Frederik Ramm
Hi,

> What about something like this:
>
>     (max_lat - min_lat) * (max_lon - min_lon) <
>         0.1 + 0.2*sin( | max_lat - min_lat | )

Sounds reasonable.

The ideal formula would probably not depend on the actual earth surface
covered but on the actual amount of OSM data. As long as entire
contintents contain less data than Central London, let people download
entire contintents ;-)

But that would require a special index to be kept which would slow down
inserts - and the whole idea was to make the system faster not slower.

Bye
Frederik

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Frederik Ramm  ##  eMail [hidden email]  ##  N49°00.09' E008°23.33'

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Re: Increase download limit near the poles?

Dirk-Lüder Kreie
In reply to this post by Petter Reinholdtsen
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Hash: SHA1

Petter Reinholdtsen schrieb:

> [Tom Hughes]
>> Well if you can come up with a good algorithm then maybe we can
>> consider it ;-) For what it's worth the current test is:
>>
>>   (max_lat - min_lat) * (max_lon - min_lon) < 0.25
>
> What about something like this:
>
>     (max_lat - min_lat) * (max_lon - min_lon) <
>         0.1 + 0.2*sin( | max_lat - min_lat | )

shouldn't that be 0.2*(1-cos( | (max_lat + min_lat)/2 | )) or similar?

- --

Dirk-Lüder "Deelkar" Kreie
Bremen - 53.0952°N 8.8652°E

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