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Units of Measure

Units of Measure

Owned by Jim Wilson
Last updated: 2018-03-13

Introduction

Consider the adjacent recipe for chocolate chip cookies. There is an obvious missing element to this: units of measure. One tablespoon of pure vanilla extract? Teaspoon? Drop? Like cooking, supply chain and field operations quantities are meaningless without knowing units of measure. AgGateway, other agriculture-industry associations, agricultural companies, and standards bodies have addressed units of measure in their standards, guidelines, and products. This page provides a starting point for implementers to understand how units of measure are used in agriculture.

Chocolate Chip Cookies

1/2 __ unsalted butter
3/4 __ packed dark brown sugar
3/4 __ sugar
2 large eggs
1 __ pure vanilla extract
1 __ semisweet chocolate chips, or chunks
2 1/4 __ all-purpose flour
3/4 __ baking soda
1 __ fine salt

Source: Food Network

Units of Measure in AgGateway Open Standards

AgGateway Open Standards specifies use of UN/CEFACT Rec 20.

Consider the following AgGateway Open Standards XML document:

Measurement XML
<Measurement>
	<MeasurementValue>50</MeasurementValue>
	<UnitOfMeasureCode Domain="UN-Rec-20">BG</UnitOfMeasureCode>
</Measurement>

In this example, a measurement element provides two child elements: MeasurementValue and UnitOfMeasureCode. One could read this as: The measurement is 50 bags. We know that the unit of measure is "bag" because the code is "BG" and "BG" is defined by UN/CEFACT Recommendation 20 as "bag". The domain attribute specifies the source of the code and must be "UN-Rec-20" (i.e., UN/CEFACT Recommendation 20). 

Units of Measure in AGIIS

AgGateway's AGIIS service supports UN/CEFACT Recommendation 20 and ANSI ASC X12 (i.e., EDI) unit of measure codes. The Excel file referenced below provides a list of units of measure specified in AGIIS product records as of the data specified in the file. It also includes a cross-reference to the X12 code list value. AGIIS supports any UN/CEFACT Rec 20 unit of measure code. Consequently, the list, which is a subset, should not be understood to be the only permitted values.

Units of Measure in AgXML

Consider the following AgXML XML document:

<QualityFactorValue unitOfMeasure="GL">1000.00</QualityFactorValue>

The example contains a single element, QualityFactorValue with an attribute unitOfMeasure. While "GL" would commonly be understood to mean "gallon", the source of the meaning "GL" is not specified. The standard does not declare that any particular code list must be used. While this may lead to ambiguity, no issues have been reported as trading-partner pairs typically agree to the code list set that applies to the messages that they exchange.

Compound Units of Measure

The concept of compound units of measure at a basic level is best explained through a couple of examples:

  • pounds per acre
  • milliliters per square meter
These examples illustrate an "x per y" pattern. The second example also includes an exponent ("squared").
Compound units of measure are commonly used in field operations (precision ag) and work within AgGateway is being conducted within the Precision Ag Council and its projects. AgGateway will update this section as deliverables are published. For concrete examples of how compound units of measure are being used today, see the Units of Measure for Field Operations below.

Units of Measure Conversion

Converting from gallons to liters or feet to meters is straightforward. Converting from anything to anything–including compound units of measure–is another. Field operations information processing often requires units of measure conversion that tend toward the more complex end of the use case spectrum. As with compound units of measure, AgGateway's Precision Ag Council and its projects are working in this area. AgGateway will update this section as deliverables are published. For concrete examples of how compound units of measure are being used today, see the Units of Measure for Field Operations below.

For concrete examples of how compound units of measure are being used today, see the Units of Measure for Field Operations below.

Units of Measure Cross-Reference and Translation

While UN Rec 20 is specified for use within AgGateway Open Standards (supply-chain-focused standards) and AGIIS supports X12 as well, field operations information requires units of measure specified in several domains with lists managed by various agencies (e.g., soil conditions, meteorology).  AgGateway's Precision Ag Council and its projects will be creating a cross-reference among various unit of measure codes lists. AgGateway will update this section as deliverables are published.

Units of Measure for Field Operations

See the Compound Units of Measure, Units of Measure Conversion, and Units of Measure Cross-Reference and Translation sections above. The referenced concrete examples are:

John Deere and MapShots provided these resources to AgGateway as examples and as input into a process to develop standards and guidelines. They are not AgGateway standards or guidelines.

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