[OSM-talk] near longitude 180

Robert Vollmert rvollmert-lists at gmx.net
Thu Feb 19 14:48:04 GMT 2009


On Feb 19, 2009, at 15:38, andrzej zaborowski wrote:

> 2009/2/19 Robert (Jamie) Munro <rjmunro at arjam.net>:
>> The right solution here is to map 0-360 degrees to the unsigned  
>> integers
>> 0-2^32. When you get an overflow, the right thing happens. It also  
>> makes
>> the most efficient use of the resolution available.

Yes, that sounds good.

> It doesn't really solve the main problem which is likely that a way
> segment connecting two nodes on the opposite sides of 180 deg can be
> interpreted as either crossing the meridian 180 or not.  And there
> doesn't seem to be a solution to that, other than "duplicating" part
> of surface, i.e. allowing nodes so be stored as having longitude of
> 181 deg or -179 deg.

No, the interpretation of that segment not crossing the meridian is  
wrong. Viewing the earth as a sphere, the segment from node 1 to node  
2 is the shorter part of the great circle going through node 1 and  
node 2.

Cheers
Robert





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