[mkgmap-dev] Empty rectangles in map

Sun Apr 25 08:31:32 BST 2021

Hi Experts,

while working on the faster-mp branch I experimented with the monster relation r9488835. I added tag landuse=forest to it so that it is actually rendered and found huge (wrong) empty rectangles in the forest.
The original file is very complex but the same problem also occurs with a simplified file, see 
http://files.mkgmap.org.uk/download/505/bad-map-split.osm.pbf
Just use e.g.
java -jar mkgmap.jar --gmapi bad-map-split.osm.pbf 
Problem: Basecamp and Mapsource don't show this map, GpsMapEdit shows a large white rectangle near 54.97743 -58.30292

I assume that we hit some unknown limit , possibly in LinePreparer or MapSplitter. 
I've also tried some older versions, so far they all show the problem.
Any idea where to look? 

RgnDisplay shows this data for the problemat area:
--------- Level 0, Subdiv 279 --------------------------------------------------
         |        |                         | final at 265f, (end 25e2)
         |        |                         | polygon start 2634 to 265f
00002634 | 000000 | 4b                      | Polygon 1
         |        |                         | Type 0x4b
00002635 | 000001 | 00 00 00                | Label offset: 0x000000 ()
00002638 | 000004 | d0 3b                   | Long delta 15312
0000263a | 000006 | 2a 3a                   | Lat delta 14890
         |        |                         | Start point 55.24913,-61.91139 2574796/-2885280
0000263c | 000008 | 0c                      | Bitstream length 12
0000263d | 000009 | bb                      | Base bb
0000263e | 00000a | 06 43 04 00 00 00 4c d1 | Bitstream (len: 12, 0xc)
00002646 | 000012 | 41 ef 00 00             | 
         |        |                         | xsame false, xneg false
         |        |                         | ysame true, yneg true
         |        |                         | xbase 16, ybase 15
         |        |                         | Coord 55.24913,-62.56851 2574796/-2915904 [-30624,+0]
         |        |                         | Coord 54.61014,-62.56851 2545017/-2915904 [+0,-29779]
         |        |                         | Coord 54.61014,-61.91139 2545017/-2885280 [+30624,+0]
         |        |                         | 0 bits left, 0
         |        |                         |  
0000264a | 000016 | 50                      | Polygon 2
         |        |                         | Type 0x50
0000264b | 000017 | 00 00 00                | Label offset: 0x000000 ()
0000264e | 00001a | d0 3b                   | Long delta 15312
00002650 | 00001c | b4 08                   | Lat delta 2228
         |        |                         | Start point 54.97743,-61.91139 2562134/-2885280
00002652 | 00001e | 0b                      | Bitstream length 11
00002653 | 00001f | 9b                      | Base 9b
00002654 | 000020 | f2 8d 04 40 a7 fe d0 4b | Bitstream (len: 11, 0xb)
0000265c | 000028 | e7 00 00                | 
         |        |                         | xsame false, xneg false
         |        |                         | ysame true, yneg false
         |        |                         | xbase 16, ybase 11
         |        |                         | Coord 54.97743,-62.51706 2562134/-2913506 [-28226,+0]
         |        |                         | Coord 55.01732,-62.54665 2563993/-2914885 [-1379,+1859]
         |        |                         | Coord 55.01732,-61.91139 2563993/-2885280 [+29605,+0]
         |        |                         | 4 bits left, 0
         |        |                         |  

Gerd