[OSM-newbies] R: R: Road Maximum speed in UK units

[Mike Harris]

... d'accord!

My only puzzle now is to wonder why I am e-mailing an Italian about speed
limits - didn't think you had them in "la bella Italia" - strange thing is
the only ticket I have ever had was in the USA ...

... And don't you just love those crazy speed limit pictures that got posted
in this thread!

Ciao!

Mike Harris

-----Original Message-----
From: Fabrizio Carrai [mailto:fabrizio.carrai at gmail.com] 
Sent: 08 May 2009 13:46
To: newbies at openstreetmap.org
Subject: [OSM-newbies] R: R: Road Maximum speed in UK units

Because you forget ""When in Rome, do as the Romans" (you teached!! ;-) )
While we are having fun, we also addressed a more serious subject:

Render max speed limits, according to WHERE you are and if and what speed
reference you need or you have.

On the contrary of you, when I'm in USA I want that my navigator alert me in
mph (and not in unuseful km/h).
In UK, I have no problem: I avoid to drive on the "wrong" side of the road
;-) !

Ciao!
	Fabrizio

> -----Messaggio originale-----
> Da: newbies-bounces at openstreetmap.org
> [mailto:newbies-bounces at openstreetmap.org]Per conto di Mike Harris
> Inviato: venerdi 8 maggio 2009 13.56
> A: newbies at openstreetmap.org
> Oggetto: Re: [OSM-newbies] R: Road Maximum speed in UK units
>
>
> Personally, when stopped for speeding on the Continent, I pretend to 
> speak
> (only) English and claim that I thought the sign meant mph - this does 
> not usually work - I can't understand why not (;>) ...
>
> Mike Harris
>
> -----Original Message-----
> From: Fabrizio Carrai [mailto:fabrizio.carrai at gmail.com]
> Sent: 07 May 2009 16:19
> To: newbies at openstreetmap.org
> Subject: [OSM-newbies] R: Road Maximum speed in UK units
>
>
>
> > -----Messaggio originale-----
> > Da: newbies-bounces at openstreetmap.org 
> > [mailto:newbies-bounces at openstreetmap.org]Per conto di Thomas König
> > Inviato: giovedi 7 maggio 2009 11.12
> > A: newbies at openstreetmap.org
> > Oggetto: Re: [OSM-newbies] Road Maximum speed in UK units
> >
> >
> > 1) Only for clarification: hour is NOT an SI-unit. So when measuring 
> > in km/h we can't complain about the ridiculous unit system in the US/UK.
>
> You  are right, but just to give a rationale to what we are
> doing: [1] says:
>
> "The SI base unit for time is the SI second. From the second, larger 
> units such as the minute, hour and day are defined, though they are 
> "non-SI" units because they do not use the decimal system, and also 
> because of the occasional need for a leap second. They are, however, 
> officially accepted for use with the International System"
>
> More info in [2]. I think that this should support the continuation of 
> the use of "hours" as time unit.
>
> >
> > 2) I think it shouldn't be too hard for a computer to convert units!
> > (Regardless of the fact if someone uses kph, kmh, k.p.h. or whatever
> > abreviation.) Isn't that what computers are made for - calculations?
> > Regarding the loss of accuracy: As speed limits are always integers 
> > (and I guess all over the world they should be divisible by 5) the 
> > computer
> > (renderer) should be able to perform the conversion without loss of 
> > accuracy!
> >
>
> Computer are built to compute, but we cannot abuse of it!
> Computing power is
> a limited resource and we shoudn't waste it doing extra calculations.
>
> Things change day-by-day, but mobile devices are still less powerful 
> than the desktop PCs.
> I think that all of you agree that we (as OSM mappers) often act as 
> "Data designer". Although the "Data Designer" objectives are different 
> than the "Application Designers" we cannot avoid to think to the use 
> of our product.
> That means that our "product" must be "usable" in the best efficent way.
>
> The reason of the discussion is to find the best way to tag the speed 
> limits avoiding extra effort during their use.
>
> So , my personal propose would be:
>
> a) Let the mappers to use their own units
> b) Set the requirements for the application to convert all such data 
> according to well know function to a SI (or an accepted unit). e.g. 
> meters for distances, km/hours for speeds
>
> Point a) is "justified" by the fact we want to map the reality and the 
> reality is that in saxon countries the signals are in Mph. As Mike 
> said ""When in Rome, do as the Romans" !
> Of course that strongly simplifies the job for the UK mappers, with 
> the request to add the info that explicit the unit. [4] indicates that 
> there is still a certain standardization. I don't know if this is the 
> best solution for a data processing application.
> We have also to say that this is still in compliant with the wiki [3] 
> "UK mappers will often include units in the maxspeed tag, ie: 
> maxspeed=20 mph (miles per hour)".
> A more literally aderence to the standard, i.e.
> "value"-space-[unit], could
> support the string tokenizer function (many of them require a 
> separating character).
>
> In my opinion that's not a detail. Think to a routing application that 
> load the speed limit indications and has to check if a unit has been 
> specified and do the proper conversion all the time. This operation 
> should have to be do done on each speed value that is in a tag!.
>
> Point b) limits the action in point a). Only standardized units should 
> be specified, since the  application shall rely on the list of the
standard.
> Still free to add "furlongs per fortnight" as unit, just specify the 
> converting function to SI in the wiki.
>
>
> Ciao!
> 	Fabrizio
>
>
> [1] http://en.wikipedia.org/wiki/Time
> [2] http://physics.nist.gov/cuu/Units/outside.html
> [3] http://wiki.openstreetmap.org/wiki/OSM_tags_for_routing/Maxspeed
> [4] http://tagwatch.stoecker.eu/Great_britain/En/tags.html
>
>
>
>
>
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