Units of Measure Standard

Energistics, the industry consortium formerly known as POSC, has released its Units of Measure Standard Version 1.0, along with a dictionary, a usage guide, grammar rules, and maps to other industry standards.

“Accurate use, exchange, and conversion of units of measure (UOM) in upstream oil and gas software are crucial,” states the introduction to the Energistics Unit Symbol Grammar Specification. “Errors in units of measure can cause serious problems for the accuracy and integrity of earth and reservoir models and the decisions that are based on those models.”

Remember that crash landing on Mars that was caused by a mix-up between feet and meters? That’s the kind of expensive mistake they are trying to avoid with this standard.

The Energistics workgroup collaborated with the Professional Petroleum Data Management (PPDM) Association and the Society of Exploration Geophysicists (SEG) to update previous standards for upstream units of measure, including POSC Unit of Measure V2.2, RP66, and OpenSpirit®. The goal was to improve accuracy and consistency of implementation, usage, exchange, and conversion of units of measure, particularly in software programs and databases. In fact, software that implements Energistics’ data-exchange standards (e.g., WITSML™, PRODML™ or RESQML™) must implement this new standard.

This standard should also be used in any correlation equations included in reports, papers and journal articles, as these may one day be coded into software programs of the future. To download the entire zipped package, visit: http://www.energistics.org/asset-data-management/unit-of-measure-standard.

So how does grammar fit into units of measure? Well, just as a sentence is constructed from parts of speech using certain rules of grammar, so a unit of measure can be constructed from a base unit and prefixes (milli–, mega–), multipliers, divisors, and exponents.

Supported Patterns      Description
a.b     Multiplication
a/b     Division
1/a     Inverse
1/(a.b)         Inverse
1E6 a   Scientific notation multiplier
1E-6 a  Negative power of ten
1/16 a  Fractional multiplier
0.01 a  Decimal multiplier
a2      Squared
a3      Cubed
a9      Ninth power
a(0.5)  Square root
a.b/c   Single factor in divisor
a/(b.c)         Multiple factors in divisor
(a/b)/(c/b)     Maximum division nesting
(a3.c/b2)/(c7/(a.b))    Complex expression

Here are a few more guidelines they recommend:
•       For multipliers between 1E3 and 0 (inclusive), use an integer number instead of an exponential multiplier. For example, use 100 ft not 1E2 ft.
•       For multipliers between 1E-2 and 1E-3 (inclusive), use a decimal fraction instead of an exponential number. For example, use 0.01 ft not 1E-2 ft.
•       For an irrational multiplier, use whole numbered ratios (where reasonable) instead of decimal fractions. For example, use 1/3 ft not 0.33333333 ft. For other fractions, use a decimal fraction such as 0.01 ft.
•       For numbers that would otherwise contain many zeros, use exponential format (e.g., 1E6 or 2.3456E-6). That is, do not use values such as 0.00000023456 or 2345600000.

For the full story, including how the new grammar differs from Recommended Practice 66, please download the new standard at:

http://www.energistics.org/asset-data-management/unit-of-measure-standard

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Grammar Quotes of the Day:

“Statistics is the grammar of science.”
–  Karl Pearson, British mathematician, 1857-1936

“Grammar, which knows how to control even kings.”
–  Moliere, French playwright, 1622-1673

“Grammar is the logic of speech, even as logic is the grammar of reason.”
–  Richard Chenevix Trench, Irish clergyman, 1807–1886

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