On Feb 19, 2009, at 12:38, Paul Ortyl wrote:
I have noticed, that some ways, which are dead-straight, are not presented as such in MapSource and Garmin (etrex Vista HCx). It looks like the coordinates have lost its precision.
Take a look at http://openstreetmap.org/?lat=48.899634&lon=8.718964&zoom=18&layers=B000FTF
The "double" crossing of Blumenheckstraße and Körnerstraße makes the straight Blumenheckstraße being distorted on Garmin. These two points should be in line with the rest of the points on Blumenheckstraße, they are not in MapSource. Some other lines, which are supposed to be parallel (they are in josm and mapnik) look really weird in MapSource.
Without further evidence, I assume this is just the low resolution of Garmin maps: coordinates are stored in map units, which are 360/2**24 degrees -- a little over 2m at the equator, less here. Those two nodes may well round to the same latitude, hence appear to be on a horizontal line. To test this, you could pass the .osm-file through a conversion to map units and back, and see what it looks like in your editor: x -> y = int(x*2e24/360.0) -> y*360.0/2e24 You might be able to devise some algorithm which displaces nodes slightly to keep straight lines closer to straight... Cheers Robert