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<body class='hmmessage'><div dir='ltr'>Hi all,<br><br>during the last weeks I tried to improve the --housenumber option.<br><br>First of all: In most cases the existing code works quite well,<br>but in many special cases it fails.<br><br>I did not yet find a good solution, so I start to describe the problems<br>with the existing code.<br><br>1) No support for random house numbers. <br>In some areas there is no obvious order in house numbers.<br>Nevertheless the current code in mkgmap always produces<br>house number data that assumes that the numbers are either<br>in ascending or descending order. We would need new data<br>structures to support this, or at least ignore random housenumbers.<br>The effect of the current code is that MapSource shows multiple <br>possible places when you enter a road and a housenumber,<br>and maybe none of the places is correct.<br><br>2) No plausibility check is done.<br>The current code assigns a house (number element) to the closest road segment.<br>It orders the houses by sorting these closest points.<br>a) This doesn't work very well when multiple houses lie at the end of a road.<br>As an effect, a house with number 12 maybe assigned to the left side of a road<br>containing only odd numbers (or vice versa), or <br>b) It also often fails when multiple houses are connected to the road with an unnamed<br>service road. In many areas you have a group with odd numbers 1-9 followed by another group<br>with numbers 11-17. Depending on the position of the houses, the calculated order might be <br>5,7,9,1,17,15,13,11 which results in an interval 5..11 instead of 1..17.<br>The result also depends on whether the service road is in the map or not .<br>c) In some areas, different road objects are created with the same road name, e.g. when <br>a p-shaped road is split or the road forms some kind of grid like this a # sign.<br>In such an area it is likely that some houses are assigned to the wrong (part of a )road.<br>d) In some cases we might be able to detect wrong OSM data as such and print<br>a corresponding message.<br><br>Both points 1) and 2) are correlated. Without a plausibilty check we cannot detect<br>the random house number case, so I think it is an interesting problem<br>of pattern recognition. The human brain is very good with that, but it is difficult to find<br>a quick and good algo for it.<br><br>Gerd<br> </div></body>
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