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<body class='hmmessage'><div dir='ltr'>Hi Steve,<br><br>I don't think that the current algo is completely wrong.<br>I think it is better to start with the complete data and divide it into <br>smaller parts as that algo keeps the information of <br>the location of elements, while your approach is likely<br>to compare many bboxes which are (too) far away from each other.<br><br>I think my last patch (mapsplit-mini-v2.patch) does not work because<br>of probems with high precision coordinates, but it also is too simple.<br>I am now working on a more complex one.<br><br>Gerd<br><br><div>> Date: Fri, 14 Nov 2014 12:05:08 +0000<br>> From: steve@parabola.me.uk<br>> To: mkgmap-dev@lists.mkgmap.org.uk<br>> Subject: Re: [mkgmap-dev] Optimizing MapSplitter<br>> <br>> <br>> Hi<br>> <br>> > I think I'll try to change this:<br>> > 1) Put large objects (large bbox, maybe only few points as with 0x4b<br>> > background polygon)<br>> > into there own sub divs and don't add small objects to those sub divs<br>> > 2) Create smaller sub divisions in dense areas<br>> <br>> I've been thinking of this way<br>> 1. Start with everything in its own subdivision.<br>> 2. For each subdivision:<br>> Find other subdivisions that completely contain it.<br>> ...but ignore subdivisions that are "too big".<br>> Combine the subdivision into the smallest of those found<br>> that still have room.<br>> 3. Repeat "enough" times.<br>> <br>> - "too big": a desktop zoomed to just the level covers less than<br>> 1000000 square units. My etrex 30 covers about 40000 square units<br>> if I measured it correctly. So I would guess that divs can be<br>> freely combined up to those kinds of sizes.<br>> <br>> But for larger containing divs, you would probably want to make<br>> sure that all elements are at least 50% of the size of the division.<br>> <br>> - "enough": I've no idea what that would mean or even if this would<br>> work at all!<br>> <br>> > I don't know yet how to do that, so I'll sleep about about again ;-)<br>> <br>> Yes that is the problem!<br>> <br>> ..Steve<br>> _______________________________________________<br>> mkgmap-dev mailing list<br>> mkgmap-dev@lists.mkgmap.org.uk<br>> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev<br></div> </div></body>
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