[OSM-talk] Mapping canals

[Nick Dyer]

Gervase Markham wrote:
> So this is just another example of why allowing people to use any unit 
> "as long as they label it" is a bad idea :-)

I am afraid that is a bit of a straw man argument.

The canals in the UK are specified in feet (for example, maximum width a 
boat can be, the length of locks, or the depth). If you translate these 
values to metres as they enter the database you are throwing away data. 
In addition, it goes against the idea that the database should represent 
the actual situation on the ground rather than something that makes it 
easy to process.

And as has been mentioned, this isn't a new problem for OSM: the 
maxspeed tag already carries values in mph - see 
http://wiki.openstreetmap.org/index.php/Talk:Map_data_Structure_Modelling 
for a subset of the discussion we are having here.

In case you're worried about all these units making the database bigger, 
it's worth noting that the string "72ft" is still shorter than "21.9456".

Nick