[OSM-talk] negative sea tiles

Lars Aronsson lars at aronsson.se
Thu Apr 26 11:52:37 BST 2007


I have seen the coastline tiles where a bunch of diagonals cut 
through and make everything a mess, apparently caused by the 400 
node limit in Frollo.  The following is a different problem.

In three places, where a piece of land (island or peninsula) cuts 
through the right hand side of a tile, but the rest of the tile is 
water, the tile becomes negative.  I'll try to draw an ASCII 
picture:

   +---------+
   |         |
   |    ......
   |   :     |
   |    ......
   |         |
   +---------+

Here, the coastline segments enter top right, go 
counter-clockwise, and exit bottom right.  The water should be on 
the outside (the right side), but instead is drawn on the inside.

I only checked close-areas.pl on one example, and the graph was 
closed with a single segment on the right of the tile.

I think I've seen all kinds of combinations of islands being cut 
in two by a tile border, but this is the only one where I've seen 
this negation happen.

My three examples are:

1. The tile http://dev.openstreetmap.org/~ojw/Tiles/tile.php/12/2190/1266.png
http://informationfreeway.org/?lat=7646904.2239&lon=1395892.708&zoom=12&layers=B000

2. The tile http://dev.openstreetmap.org/~ojw/Tiles/tile.php/12/2189/1269.png
http://informationfreeway.org/?lat=7616721.1589&lon=1385153.30785&zoom=12&layers=B000

3. The tile http://dev.openstreetmap.org/~ojw/Tiles/tile.php/12/1848/1878.png
http://informationfreeway.org/?lat=1659296.90255&lon=-1951169.37965&zoom=12&layers=B000


-- 
  Lars Aronsson (lars at aronsson.se)
  Aronsson Datateknik - http://aronsson.se




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