This week's weeklyOSM [1] included a suggestion to minimize the number
of fuel:* subkeys, which reminded me that the fuel tagging situation in
the United States is actually quite complicated. The same generic grade
of gasoline ("regular", "mid-grade", "premium") may have a different
octane rating at one gas station than the station across the street, and
each state has a different standard for the minimum octane that may be
labeled with a particular grade. [2] What would be sold as premium
gasoline in Alaska would be regular in South Carolina.
Compounding the matter, for several years, the fuel:* wiki page has
specified that octane ratings must be expressed in RON, which is used in
more countries. [3] In a few countries including U.S., octane ratings
are only posted in RON, not AKI. Converting between AKI and RON would
require knowing the MON, which AFAICT isn't published anywhere.
Wikipedia does offer estimates for regular and premium grade, but they
aren't reliable or specific enough to use as subkeys. [4]
I've updated the wiki page with statistics demonstrating that octane
ratings are consistently mapped based on AKI in the U.S. [5] (If I'm
wrong about this, then OSM is a better resource for finding unlawful
stations than lawful stations.) It stands to reason that mappers would
tag what they can plainly see rather than learn the intricacies of
metrology.
From a data consumer's perspective, it's unfortunate that there's no
single worldwide standard. But I think more data consumers would need to
differentiate between different grades in the same region than across
national boundaries. If we do want to remove the current ambiguity, we
could define separate fuel:ron_* and fuel:aki_* subkeys, but that seems
like a lot of work for little gain.
[1] http://weeklyosm.eu/archives/12232
[2] https://en.wikipedia.org/wiki/U.S._State_Fuel_Octane_Standards
[3] https://wiki.openstreetmap.org/wiki/Special:Diff/1033280
[4] https://en.wikipedia.org/wiki/Octane_rating#Measurement_methods
[5] https://wiki.openstreetmap.org/wiki/Key:fuel#United_States
--
m...@nguyen.cincinnati.oh.us
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