[mkgmap-dev] echo improvements for elements with fake ids

Tue Jan 20 22:23:54 GMT 2015

Hi Mike,

that's a good idea to tackle the fake id problem.

I didn't have time to test it but after a short look over the committed 
patch I think there are a few things to be improved:

First of all small stylistic things: fields should start with lower case 
letters. So OriginalId in Element should be originalId.
It would be good if you add (javadoc) comments to your source code :-)

It seems that the ways created by Multipolygon relations use the 
relation id as original id. I am not sure if that's the best choice. 
It's not easy to decide which id should be chosen when ways are merged. 
When using the relation id it should be clear in the output that this id 
is the relation id and not a way id. Otherwise users will search for 
completely wrong ways.

WanMil

> HI Gerd, thanks for that – I was scratching my head trying to think of a
> way that would use less memory. If using the tags, each tag would have
> used more than 8 bytes, although they would have only been on faked
> elements. The tag iterators would also have processed them (unless
> special code was included to exclude them). I did wonder whether we
> could store both the original Id and the fake Id in the 64 bit number
> with perhaps 40 bits for the OSM Id and 24 bits for the fake Id, but
> this might not be enough space (taking into account the future).
>
> Mike
>
> *From:*Gerd Petermann [mailto:gpetermann_muenchen at hotmail.com]
> *Sent:* 19 January 2015 20:29
> *To:* mkgmap-dev at lists.mkgmap.org.uk
> *Subject:* Re: [mkgmap-dev] echo improvements for elements with fake ids
>
> Hi Mike,
>
> I've committed the patch as is. The memory impact is not that big as
> we have typically less than 500.000 instances of Element in one tile,
> so 8 more bytes * 500.000  ~ 4MB more heap.
>
> Gerd
>
> From: mike at tvage.co.uk <mailto:mike at tvage.co.uk>
> To: mkgmap-dev at lists.mkgmap.org.uk <mailto:mkgmap-dev at lists.mkgmap.org.uk>
> Date: Mon, 19 Jan 2015 11:55:00 +0000
> Subject: [mkgmap-dev] echo improvements for elements with fake ids
>
> The attached patch improves the echo and echotags messages by including the
> id of the original element when a fake id is generated by mkgmap, thus
> enabling you to find it in OSM.
>
> Please try, and commit if you are happy with the change.
>
> Regards,
> Mike
>
>
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