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Links to resources of further interest
 
System and Graphics Design and Implementation by Spatial Systems
Spatial Systems Billings, MT (406) 256-2033
 
Environmental Consulting and Project Management by Bison Engineering
Bison Engineering
 

Data Validation

All real-time data reported by the air quality monitoring stations through this website is provisional and subject to revision. The reported values are subject to significant change and are not citeable until validated.

The measuring systems are subject to various effects including:

  • Calibration drift,
  • Instrument malfunction,
  • Data transmission problems, and
  • Operator overrides during maintenance.
Therefore, the values are screened by environmental scientists to correct or eliminate invalid data prior to submission to the responsible regulatory agencies such as the EPA and the Montana Department of Environmental Quality.

The provisional measurements reported on this web page have been screened for reasonableness, but not reviewed or validated. This means that there will be occasional differences between this preliminary information and the reports eventually submitted to the agencies.

Data validation includes tests to find any indications of problems with the measuring instruments, evidence of miscalibration, clock errors or other flaws in the measurement process. Certain types of errors require that the reported value be deleted and replaced by an void data code. Certain other cases can be corrected under standard operating procedures approved by the site owners and the regulatory agencies.

Other parts of the quality assurance process include:

  • daily self-tests performed automatically to verify that the instruments are functioning normally,
  • monthly performance tests performed by site operators to verify accurate calibration of the instruments, and
  • quarterly 'audit' tests performed by independent entities to verify both accuracy and overall conformance with standard operating procedures.

The site 'audits' provide cross-checking of calibrations between different entities, and include participation by Montana Air Quality Bureau and US EPA technical representatives.

Historical data retrieved from the archives on this site includes both provisional data reported in real time by telemetry from the monitoring stations and validated data from reports sent to the regulatory agencies. Validated data archives normally become available 6 to 9 months after the measurement date.