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An estimate of the quantity of pollutant emitted within defined geographic, temporal, sectoral, and/or procedural boundaries. Inheritance




Property Type Definition
activityDataValueList Collection A list of values for the activity data included in the emission estimation equation used to produce the EmissionMetric.
description Text A description of the process of applying the emission estimation methodologies to available data to determine the value of the EmissionMetric.
emissionFactorValueList Collection A list of values for the emission factors included in the emission estimation equation used to produce the EmissionMetric.
estimationMethodologyList Collection A list of methods and algorithms used to estimate emissions.
fuel Fuel  
inventory Inventory The parent inventory to which the EmissionMetric belongs.
lowerBound Float The lower bound of the emissions estimate expressed at the 95% confidence limit.
parameterValueList Collection A list of values for the parameters included in the emission estimation equation used to produce the EmissionMetric.
place Place The area, facility, location, or point-source to which the EmissionMetric applies.
pollutant Pollutant The emitted chemical or agent the EmissionMetric measures.
qualityControl Text A textual description of the quality assurance and quality control measures applied to the estimation of the EmissionMetric.
sourceCategory SourceCategory The classification of emissions by emitting activity or economic sector to which the EmissionMetric belongs.
timePeriod PeriodOfTime The time period over which the relationship applied.
uncertainty Text A textual explanation of factors affecting the uncertainty of the EmissionMetric value.
units Text The unit of measurement that applies to the estimated emission value, lower bound, and upper bound.
upperBound Float The upper bound of the emissions estimate expressed at the 95% confidence limit.
value Float The estimated amount of pollutant emitted.
valueCO2e Float The amount of equivalent carbon dioxide (CO2e) that would generate a global warming potential equal to that of the emitted pollutant(s), as measured in gigagrams (Gg).

Key Relationships


Each EmissionMetric will have a parent Inventory, representing the inventory that includes the EmissionMetric.


An EmissionMetric may relate to a single Pollutant, SourceCategory, and/or EstimationMethodology object.  When an EmissionMetric does relate to one of these objects, the object defines the pollutant, sectoral, or methodological boundary of the metric.  When an EmissionMetric does not relate to a Pollutant, SourceCategory, or EstimationMethodology object, the EmissionMetric does not have the associated boundary.


An EmissionMetric object may relate to ParameterValue, ActivityDataValue, and EmissionFactorValue objects that represent the parameters, activity data, and emission factors used by the EstimationMethodology used to generate the EmissionMetric.  Note that ActivityDataValue and EmissionFactorValue are child classes of ParameterValue.

Click image to enlarge.  The EmissionMetric class is both a “storage engine” for emissions statistics, and the schematic hub that connects other classes in the inventory schema.


The EmissionMetric class represents emission estimation metrics reported by inventories, and places those metrics in their proper context by associating them with ample amounts of structured metadata.  An EmissionMetric object reports the emission metric itself using the value, units, lowerBound, upperBound, and valueCO2e properties, provides textual context with the description, uncertainty, and qualityControl properties, and establishes the boundaries of the reported metric with the estimationMethodology (methodological), geographicCoverage, location (geographic), pollutant (pollutant), sourceCategory (sectoral), and timePeriod (temporal) properties.

In addition, the paramaterValueList, emissionFactorValueList, and activityDataValueList properties link the EmissionMetric to the specific parameters used in the emission estimation equation.

With its dual role as a “storage engine” for emission statistics and schematic hub associating static Pollutant, SourceCategory, EstimationMethodology, Parameter, EmissionFactor, and ActivityData objects with reported metrics and each other, the EmissionMetric object is the foundational class in the common air pollutant inventory framework.

The EmissionMetric class is extremely flexible, and may represent three distinct types of EmissionMetric objects.

  • An atomic EmissionMetric object represents an emission estimation made at the most detailed level possible, based on the estimation methodologies used within a source category.  For example, many source categories report metrics (or are built upon metrics reported) at the point-source level.  An atomic EmissionMetric would link a specific Inventory, Pollutant, SourceCategory, EstimationMethodology, and Location, reporting a metric specific to the point-source.
  • An additive EmissionMetric object represents an emission estimation made by totalling atomic EmissionMetrics.  Within a GHG Inventory, the total CO2e emitted from all sources would be represented by an additive EmissionMetric object.  For source categories that apply estimation methodologies at the point source, the total emission of a specific Pollutant within the SourceCategory would be represented by an additive EmissionMetric object, which would contain a pollutant property and a sourceCategory property, but would not contain an estimationMethodology or location property if more than one estimationMethodology or location were applied within the SourceCategory.
  • An empty EmissionMetric represents an assoiation between an Inventory, Pollutant, SourceCategory, EstimationMethodology, and/or geographic boundary that does not have a reported metric associated with it.  For instance, if an Inventory were to list estimation methodologies used to project emissions of a pollutant with a source category without reporting the metric derived from each estimation methodology, empty EmissionMetric objects would be used to represent each association between Inventory, Pollutant, SourceCategory, and EstimationMethodology.