[OSM-dev] Free mapping software

[lars]

bvh wrote:

> It seems there has been talk about using bezier segments.
> What's the status on that?

Many of us here are new to GIS, but have a general computing and 
graphics background.  It is natural to think of bezier curves, but 
it appears nobody in GIS use them, and probably for a good reason. 
It gets only too complicated when mixed with map projections.

The solution we in OpenStreetMap (and apparently everybody else in 
GIS) use is to use only linear (straight) line segments and to 
make them so short that any change in map projection cannot 
introduce any significant errors.  That is, the segments are 
drawn as straight lines both before and after any change in 
projection.

Since our data is based on GPS positions from consumer-level 
products, the error margin is always larger than 1 meter but 
hopefully less than 10 meters.  So any change in map projection 
should never be allowed to move the center of a line segment more 
than 1 meter to the side.  I haven't done the math, but I guess 
this means line segments should be kept shorter than 200 or 300 
meters.

We don't really enforce this, but you can download the latest dump 
from http://planet.openstreetmap.org/ and analyze if we have any 
overly long segments.  If you identify any very long segments, you 
can make a list of areas where we need to improve.  Please post 
your findings.


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