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Calibration workflow

Use the calibration workflow to fit the model of an emission source to reference measurements. The workflow compares the model results with the measured values. It finds the model parameter values that give the best fit, and it computes the uncertainty of the model. A calibration applies to its pipeline from its Valid from date.

Before you start​

  • You must have the SuperAdmin role.
  • The emission source must have a pipeline with a model.
  • You must have one completed measurement workflow minimum. You can also use measurement campaigns from other emission sources.
  • The process data for the measurement periods must be in WS.PEMS.

Start the workflow​

  1. In the menu, open Calibration workflows. The Workflow Manager opens.
  2. Click the Calibration tab.
  3. Click Start Calibration.
  4. In Create calibration, select the Pipeline and the Valid from date.
  5. Submit the form. The new calibration workflow opens.

Steps​

The workflow page shows the Calibration Overview and the list of steps. Each step is marked as complete, current or upcoming. Click a step to open it. Each step has a button that validates the step and opens the next step. Click Previous to go back one step.

Step 1: Create Calibration​

This step is complete when the calibration is created.

Step 2: Select Measurement Dataset​

  1. In Where to look, select where to find measurement campaigns: This emission source, This asset, This region, Everywhere or Imported.
  2. In Measurement campaigns, select one campaign or more.
  3. Optional: change the Weight of a campaign. Weight 1 is neutral. A weight must be more than 0.
  4. Optional: for a campaign from another emission source, limit the process values that the calibration uses. Leave the field empty to use all of them.
  5. Optional: click Preview the calibration dataset to see the dataset before you continue.
  6. Validate the step.

A campaign from different equipment is marked in the list. Use such a campaign only when the equipment is comparable.

Step 3: Select Calibration Dataset​

  1. In Request data, select the process and computed values to plot. Select the Data source: Calibration dataset or First-level data.
  2. Click Request.
  3. On the graph, remove the periods that you do not want in the fit.
  4. Click Select dataset.

Step 4: Calibrate Pipeline Steps​

  1. In Calibrate pipeline steps, select the Parameter to calibrate. Set the start value and the limits, and the maximum number of iterations.
  2. Click Calibrate. The calibration can take some time.
  3. Examine the result in Calibration Results: the Initial Value and the Calibrated Value of each parameter, and the objective function.
  4. Optional: click Run Test to run the pipeline with the calibrated values on the dataset. Compare the result with the measurement.
  5. Click Update Model config to write the calibrated values into the model configuration. You can revert the parameters to their original values.
  6. Optional: click Update Tag Limits to update the limits of the tags.
  7. Validate the step.

Step 5: Run Model​

  1. In Run on, select one option:
    • The calibration's timestamps: runs the model on exactly the instants of the fit. Use this to compare the results with the fit.
    • A period: runs the model on every instant in a date range. Use this to see how the calibrated pipeline behaves outside the fit.
  2. Select the pipeline steps to run, or click Select all steps.
  3. Click Run Model. The results go to the first-level data of the emission source.

Step 6: Compute Calibration Load Ranges​

  1. Set the Minimum Range Width and the Minimum Values per Range.
  2. Click Compute Ranges. The Load Ranges table shows each range and its number of points.
  3. Optional: change or remove a range, then click Update Ranges.
  4. Validate the step.

Step 7: Init Uncertainty​

  1. In Initialize compute uncertainty parameters, click Create to make an uncertainty parameter version. Click Update to change an existing version.
  2. In Compute uncertainty parameters, select the Output Standard Tags and the Points per load range.
  3. Start the computation.

Step 8: Uncertainty results​

  1. In Uncertainty Results, examine the computed values: Sensitivity, Correlation, Calibration Uncertainty, Input Uncertainty and Measurement Uncertainty.
  2. Optional: edit a value. To go back to the computed values, click Reset Input Uncertainty to Defaults or Reset Measurement Uncertainty to Defaults.
  3. Validate the step.

Step 9: Generate Documentation​

  1. In Calibration Documents, select the Standard Tags.
  2. Validate the step. The calibration is complete.

Result​

  • The calibrated parameter values are in the model configuration of the pipeline, if you clicked Update Model config.
  • The uncertainty parameter version holds the computed uncertainty for the emission source.
  • The calibration shows on the Calibration tab of the Workflow Manager. Click Export in the Actions column to export the measurement values and the process values.

The Generate Documentation step completes the workflow. It does not create a document file. Use Export to get the data.

Common problems​

ProblemWhat to do
"Choose at least one measurement campaign."Select a campaign in step 2. If the list is empty, select a wider scope in Where to look.
"Every weight must be a number greater than 0."Set the weight of each selected campaign to a number more than 0.
"Some campaigns contributed nothing"No process data matched the measured period of that campaign. Make sure that the process data for the period is in WS.PEMS, and that the measurement workflow has the correct time zone and offset.
"Some timestamps skipped" in Run ModelSome timestamps of the calibration have no first-level data on this emission source. Use A period, or calibrate first.
"Period missing"Give both a start and an end for the period.
"No uncertainty parameter version found."Complete step 7 first.
An error says that the step is not allowed.The workflow is not at that step. Complete the steps before it first.