#599 Ton and Tonne

John MacEnri Wed 28 Mar

I raised this question on the SkySpark forum, but putting it here to elicit feedback.

I've noticed that the Haystack units database has taken t as the unit symbol for the American Short Ton (2,000 pounds and 907.18474 kg) and ton as the unit symbol for the Metric Tonne (1000 kg)

This seems opposite to what it should be. The symbol t is normally used as the unit symbol for the Metric Tonne and the words Tonne and Ton are normally used to distinguish the Metric from American. But with ton being used as the symbol for the Metric Tonne, it's adding a lot of confusion for some of our clients as to what mass/weight we're actually talking about.

Is there any appetite out there for changing this or is everyone happy with the way round it is currently. Brian's feeling was that is it was unanimous to change, then it could be changed, but as it's a breaking change, it would not be likely.

Just to clarify, I'm speaking from an Irish/European perspective on this.

Thanks, John.

Leroy Simms Thu 29 Mar

+1 for changing.

Chris Owens Thu 29 Mar

+1 for aligning with existing standards. Wikipedia says that t has been the standard abbreviation for metric ton (tonne) ever since 1879

Alex Bible Fri 30 Mar

Using t seems a bit arbitrary for either ton or tonnes.

Since haystack is an international community, we should make sure to provide a very clear differentiation between the two units.

My proposal would be for ton and tonne to be the standard units.

However, it seems that we could have an issue if there needed to be further differentiation between a US and an Imperial ton. The US generally uses a 2000 lbs ton, or a short ton, where as other countries using imperial units may use a long ton which measures out to 2240 lbs.

I would put a vote in for:

  • ton - US Ton (2000 lbs)
  • longton - UK Ton (2240 lbs)
  • tonne = Metric Ton (1000 kg)

Chris Owens Fri 30 Mar

+1 for Alex's suggestion. t is supposed to be only for the metric ton, but is widely (ab?)used for the US Ton. Alex's suggestion is unambiguous. And t could be deprecated and left in place so as not to break any existing code.

John MacEnri Tue 3 Apr

In order for a change to be non-breaking, we can't change the meaning of either of the existing symbol assignments.

Therefore t would have to remain used for US Ton, but possibly deprecated somehow? And ton would similarly have to remain as a (deprecated) symbol for Metric Ton.

I like the idea then of having a new symbol assigned for Metric Ton being tonne, and have two other new ones, being shortton or ston for short :-) And longton as suggested for UK Imperial Ton.

Brian Frank Fri 2 Nov

Just to revisit this, since I don't think we have a clear proposal yet. The current definitions are:

metric_ton, ton; kg1; 1000.0
short_ton, t; kg1; 907.18474

The full names are descriptive, we are really talking about ton and t abbreviations and if there should be a new tonne abbreviation.

But we also have these definitions to consider:

// mass flow
metric_tons_per_hour, ton/h; kg1*sec-1; 0.2777777777777778

// power
tons_refrigeration, tonref; kg1*m2*sec-3; 3516.853

// energy
tons_refrigeration_hour, tonrefh; kg1*m2*sec-2; 1.26606708E7

Any change to the mass definitions should probably align with others

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