[OSM-talk] Mapping canals

Andy Robinson (blackadder) blackadderajr at googlemail.com
Thu Jan 24 11:12:45 GMT 2008


Gervase Markham wrote:
>Sent: 24 January 2008 10:34 AM
>To: talk at openstreetmap.org
>Subject: Re: [OSM-talk] Mapping canals
>
>Sven Grüner wrote:
>> I don't know of any country using the metric system that is familiar
>> with the term "kph". The unit symbol is "km/h" and so everbody uses
>*kmh*.
>
>Google understands kph:
>http://www.google.com/search?ie=UTF-8&oe=UTF-
>8&sourceid=navclient&gfns=1&q=30mph+in+kph
>
>So this is just another example of why allowing people to use any unit
>"as long as they label it" is a bad idea :-)
>

Google and other data users are provided with their data in detailed and
specified formats by external contractors. They know at the outset what the
units for a given data set are. Thus it's relatively easy for them to
provide a response to users with any suitable conversion they wish.

You could decide on a strict set of tags for OSM and use these to define
certain attributes. That’s fine for making it easier to code and deliver
reliable data to users but absolutely useless if this precisely formatted
data doesn’t exist in the database, and that’s the reality we face.

Contributors of data to OSM are not professionals working to a strict code
of practice, so we can never guarantee that general contributions will be in
metric, imperial or wigets. If a group of OSMers wish to set up a strict
standard following process then that’s fine but of course it's going to be
limited to small amounts of data and small geographical areas.

The alternative is to accept the limitations of the model and work out ways
of using what data exists in a flexible way. If the units are given then
it’s a doddle (even if the form varies), if no units are given then it is
most likely the unit implied is the convention for the location (eg miles
for UK, USA or km for rest of Europe etc).

OSM will always need smart and sophisticated processing. 

Cheers

Andy





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