Quality assurance

Data  quality  allows  users  and  user  systems  to  assess  fitness  for  use  of  the  provided  data.  Data quality measures and the associated evaluation are reported as metadata of a data product. This metadata improves interoperability with other data products and provides usage by user groups that the data product was not originally intended for. The secondary users can make assessments of the data product usefulness in their application based on the reported data quality measures.

For this <L3 Gridded MBES Data Specification> the following Data Quality Elements will be assessed [1]:

• Conformance to this Product Specification

• Intended purpose of the data product

• Completeness of the data product in terms of coverage

• Logical Consistency

• Positional Uncertainty and Accuracy

• Thematic Accuracy

• Temporal Quality

• Resolution

• Data Fliers

• Data (Sounding) Density

• Data Gaps (Holidays)

• Aggregation measures

• Validation checks or conformance checks including:

  • General tests for dataset integrity;

  • Specific tests for a specific data model.

Quality references in the Abstract and/or Lineage, although the ISO19115 Data quality elements within (MD_DataQuality) can also be used to document precision and accuracy more fully.

Using QAX

Quality assurance on L3 data using the MBES Grid Checks and Finder Grid Checks plugins in QAX is mandatory.

QAX is an open-source project, jointly steered by AusSeabed, the United States of America National Oceanic and Atmospheric Administration’s Office of Coast Survey (NOAA OCS), and the University of New Hampshire’s Center for Coastal and Ocean Mapping (UNH CCOM). QAX version 1.0 is available on the AusSeabed GitHub (https://github.com/ausseabed/qax/releases ).

QAX facilitates quality assurance (QA) of MBES data. It provides an efficient workflow for L3 MBES bathymetry data when density and uncertainty/standard deviation attributes are also available. The tool standardises QA outputs and assists technicians to perform a robust QA of data.

QAX assessments must be performed within the data structure submitted to AusSeabed. The qajson file and screen capture of the QAX summary (Fig. 1) are required along with raw data on submission to AusSeabed.

Open

Figure 1. An example of screen capture of the result summary from QAX for L3.

For full details on Quality Assurance see the AusSeabed Quality Assurance Framework

Published Products will contain a Statement of Quality Report with a star rating.

The Statement of Quality helps ASB’s end users decide how to best use a published dataset. The SOQ describes the characteristics of quality according to a standardised list of dimensions. Each dimension contains a list of questions that are asked of the dataset to help end users understand rating given. The determination of quality is made post processing and is not reflective of source or collection.   

The SOQ is constructed through a collaborative process that aims to answer targeted questions. The Data Manager for ASB data is charged with ensuring the process is collaborative and accurate. The questions used for reporting are based on the following six dimensions of quality:  

• Accuracy  

• Completeness  

• Consistency  

• Integrity 

• Uniqueness  

• Validity