[Tagging] Straw pole Temperature=objective default unit?

Philip Barnes phil at trigpoint.me.uk
Thu Apr 9 17:24:44 UTC 2015

On Thu, 2015-04-09 at 14:39 +0200, Martin Koppenhoefer wrote:
> 2015-04-09 2:52 GMT+02:00 Warin <61sundowner at gmail.com>:
>         Say a mapper tags
>         temperature=42
>         The options are to interpret this as;
>         a) values would be interpreted as degrees Celsius. (Similar to
>         the width key default.)
>         b) values would interpreted by region. Most of the world would
>         be Celsius, USA would be Fahrenheit. (Similar to defaults for
>         speed on roads.)
>         c) No default unit. All entries would require a declaration of
>         the units used. Thus this would be an incorrect entry and
>         ignored.
> units should be preferred to remove ambiguity. In case of missing
> units, you will have to guess what unit was intended, typically
> considering 
> a) what you expect to be the right value for the particular feature /
> situation, and 
> b) according to the region this was entered, and
> c) according to the user that entered the number without unit
> etc.
>         Please indicate your preference a,b or c. (or d etc if they
>         are nominated?)
> why? Interpreting the data is something that dataconsumers have to do,
> everyone can decide to do this the way she likes (e.g. drop the value,
> assume a region default, etc.). For the sanity of our db it should be
> suggested to add the unit always and not to rely on any default.
I absolutely agree Martin, for data sanity and peer review adding the
units would help improve the quality of the map.

The UK is officially metric, although we retain miles and pints, but
usage is sparse. Despite being in my 50s and have never had a science
lesson taught in imperial units, they still remain in common usage.
Normal people do still ask for loose meat, cheese etc in imperial units
and the person serving then converts to metric in their head.

I am happy working with either, my GPS is set to metric as thats the
system I prefer in that context, beer belongs in pints. 

Whilst I am struggling to think of a mappable feature on which I can add
a temperature tag, speed limits mapped without mph are easy to spot. The
review issue/concern is elevations. OS maps have been metric since the
70s, however out-of-copyright OS maps are imperial and 300ish is valid
height in Shropshire, whether it be feet or metres. 

When mapping speed limits I find no issue with adding mph, josm
remembers anyway so why is entering kph such a hardship? It would
certainly make our data more robust and easier to check.

Phil (trigpoint)

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