roberti lter asm_september2015_jr_ds_jt_jc

© 2013 National Ecological Observatory Network, Inc. ALL RIGHTS RESERVED.

CONNECTING UNCERTAINTY ESTIMATES AND QA/QC

METHODSJosh RobertiDerek SmithJeff Taylor

Janae CsavinaDave Durden

Stefan MetzgerSarah Streett

LTER All Scientists Meeting1 September 2015

Estes Park, CO


TRACEABLE – STANDARDIZED – TRANSPARENT

• In-house calibrations• Algorithm Theoretical Basis Documents (ATBDs)

http://data.neoninc.org/documents• Theory of measurement• Theory of algorithms

• converting from raw, uncalibrated data• QA/QC • Temporal averaging (Level 1 data products)

• One- and thirty-minute averages• Uncertainty estimates

• Measurement uncertainty as well as the uncertainty of our temporally averaged data products

http://data.neoninc.org/documents




NEON’S CVAL

Purpose of having an in-house metrology lab Nationwide Sensor Based Observations

Thousands of sensors through one lab using same nationally recognized standards.

Control over quality and internal assessment of measurement uncertainty. terrestrial and aquatic sensors gas and isotopic water transfer standards standards calibrations external labs

Technology changes Compare old to new with same standards to

understand changes in the 30 years of the project.

© 2015 National Ecological Observatory Network, Inc. ALL RIGHTS RESERVED.NEON is solely sponsored by the National Science Foundation

QA/QC Flags:• Range – realistic data range• Persistence – realistic data variability• Null –missing data points• Gap –large data gaps• Step –large changes between

consecutive data points• De-spiking –spikes in the data set• Consistency – comparable

measurements

Sensor Flags:• Identify problem areas, e.g.,

consistency checks

• Assist algorithm refinement and development

QA/QC


UNCERTAINTY ESTIMATES

NEON calculates measurement uncertainties according to recommendations of the Joint Committee for Guides in Metrology (JCGM) 2008.

where , = partial derivative of y with respect to xi

= combined standard uncertainty of xi.

aka QA/QC


Example1. Convert [Ω] to [°C] 2. Sensor flags

A. Heater (ON/OFF) B. Turbine (flow >

threshold)3. QA /QC testing4. Calculate temporally averaged data product5. Publish data

1 Hz Tem. (Ω)

• Inform assembly uncertainty to set thresholds for certain QA/QC tests (e.g., persistence)

• Make confident inferences between signal (environmental phenomenon)-to-noise

• Promote standardization and interoperability among ecological networks

Traceable uncertainty estimates


Future work• Data commissioning

• Audits• Threshold refinement• Non-analytical uncertainty analyses

• Bayesian – Monte Carlo

Thanks!

[email protected] info:

mailto:[email protected]