Overview
The Data Stewardship team is responsible for documenting calibration procedures for instruments, where applicable. There are many facets of instrument calibration which are outlined in the sections below.
For access to calibration records for a specific instrument and time period, please put in a Technical Support request (Oceans 3.0 Help) or navigate to Oceans 3.0 website and click on "Request Support" link at the top right of the web page. A data steward will be assigned to compile the requested information.
Manufacturer Calibration Sheets
If the vendor is required to provide a calibration sheet along with the delivery of an instrument to Ocean Networks Canada, the data stewardship team is responsible for the proper storage of the documentation.
The calibration sheet, upon recovery, is moved to device-specific Alfresco (a content management system) directory with a date prefix referring to the date on which the calibration was performed by the vendor. This ensures maintenance of historical records of all calibration procedures performed on an instrument during its lifecycle. These directories are not publicly available, but files can be provided upon request.
Sample Calibration Sheet
The following is a calibration sheet for a Sea-Bird SeaFET V2 pH Device (Device ID 48000). The calibration procedure was carried out by the vendor Sea-Bird Scientific and sent along with the instrument to Ocean Networks Canada where it was stored in our document repository.
The document lists all relevant details such as date of calibration, calibration coefficients, which are used within Oceans3.0 (see details here CalibrationCoefficients), and a pressure test certificate.
Calibration Formulas
Calibration formulas are applied to individual sensors within Oceans 3.0. The calibration formula can contain anything from simple mathematical equations to complex conditional statements and may refer to other sensors within the Oceans 3.0 framework. For example, calibration of the External pH (Dynamic Salinity) of a Sea-Bird SeaFET V2 pH device uses the temperature sensor of a collocated CTD device in its calibration formula. It also includes details of the parameters used and the functions called.
The calibration parameters may change during a device's lifecycle as it undergoes several calibrations. To maintain a record of all calibrations applied to a sensor in Oceans 3.0, any change in the formula or parameters is performed through an entirely new calibration procedure entry with an Effective Date From.
Accessing Calibration Formulas in Oceans 3.0
Users can see calibration formulas applied to sensors within Oceans3.0 by following these steps.
- Navigate to the device within Ocean3.0 and open its Sensor tab.
Note: You can either search for a device by navigating to More > Infrastructure > Device Search or if you already know the device ID, you can plug it into this URL to directly open the device page (replace XXXXX with device ID) https://data.oceannetworks.ca/DeviceListing?DeviceId=XXXXX. - Identify the sensor you are interested in and click on the Sensor ID hyperlink. You will be redirected to the Sensor Maintenance page.
- The first tab on the bottom half of this page is the Calibration tab and will list all calibrations added for this sensor. If there are multiple entries, the Date From field can be used to identify the current calibration formula applied to the device. The Date From field can also be used to identify calibration formulas applied in the past or formulas that will come into effect in the future. If the tab is blank, there are no calibration records for this sensor.
- Examples:
- CO2 Partial Pressure sensor of the Pro-Oceanus CO2-Pro CV device.
- Chlorophyll sensor of the Turner Cyclops-7 Fluorometer device.
Calibration Coefficients
Calibration coefficients are often stored under Additional Attributes of a device. All such coefficients are labeled as "Calibration" in order to identify them and are accompanied by a short description and any relevant additional comments such as their downstream application.
Similar to calibration formulas, these coefficients can also change over a device's lifestyle. These changes are accommodated with a brand new entry with an Effective Date From in order to preserve all historical records.
Accessing Device Attributes in Oceans 3.0
Users can see calibration formulas applied to sensors within Oceans 3.0 by following these steps.
- Navigate to the device within Ocean 3.0 and open its Additional Attributes tab.
Note: You can either search for a device by navigating to More > Infrastructure > Device Search or if you already know the device ID, you can plug it into this URL to directly open the device page (replace XXXXX with device ID) https://data.oceannetworks.ca/DeviceListing?DeviceId=XXXXX. - Look for all attribute(s) with the label "Calibration" which represents the coefficient(s) used in the calibration procedures of this device. The Date From field can be used to identify when a particular coefficient came into effect.
Note: Unlike calibration formulas, only the currently applied calibration coefficients can be accessed by the end-user. Historical records of coefficients are stored in the database, however, they are not accessible on the UI. - Examples
Driver initializations
Every instrument (which uses drivers) returns a specific set of commands during its initialization procedure. Among other details such as self-identification, configuration settings, and piggybacks, the commands also return the coefficients used for calibrating the instrument. These commands are stored in log files that are archived by Ocean Networks Canada, thus providing long-term storage of calibration records as well as allowing for the verification of calibration formulas used within Oceans 3.0. These daily log files can be obtained from the Data Search as a data product.
To find log files with initialization sequences, go to the Annotations Search, choose resource type of 'Device Data', Resource of desired instrument and optionally enter a date range. After clicking search, a list of annotations will be produced. Those that have '(Start Command)' within the Annotation Summary correspond to dates with driver initializations.
In-situ/pre-deployment calibration
Some calibration procedures are performed prior to the deployment of a device. These can include:
- Ferry benchmark testing
Oxygen optode sensors deployed on ferries are subject to biofouling and changes in data measurements in shallow marine environments. Therefore, a reference Optode is used to take benchmark measurements and then compared to the deployed Optode on the ferry. Benchmark log sheets and measurement data are archived in respective device-specific Alfresco directories and a corresponding device action is added with the label "Benchmark Sensor Measurement". An example of this can be seen under the device actions of Aanderaa Optode 3835 (S/N 1797). - Compass calibration
Imagenex Sonars deployed with an Azimuth Drive need to have their heading calibrated since the factory calibration is performed with the sonar pointing down while the Azimuth Drive is deployed at sea with the sonar pointing up. - Camera calibration
Underwater cameras have to be calibrated for colour balance and optical distortion. This is usually done with a checkerboard such as ISO_12233-reschart. - Pressure offset
Nortek Aquadopp Current Meter devices do not measure pressure automatically, so a pressure offset has to be set manually to make corrections for the local atmospheric pressure where the instrument is to be deployed.
Physical samples
Physical samples are collected for ground-truthing and verifying data. The most common case is Niskin water samples processed through Winkler Titration in order to validate cabled oxygen sensors.
Post calibrations
For some devices, such as Hydrophones, calibrations are conducted after the instrument is recovered in order to assess drift from the pre-deployment calibration. These calibration documents are stored in a device-specific directory with a date prefix referring to the date on which the calibration is performed.