SAQA All qualifications and part qualifications registered on the National Qualifications Framework are public property. Thus the only payment that can be made for them is for service and reproduction. It is illegal to sell this material for profit. If the material is reproduced or quoted, the South African Qualifications Authority (SAQA) should be acknowledged as the source.
SOUTH AFRICAN QUALIFICATIONS AUTHORITY 
REGISTERED UNIT STANDARD THAT HAS PASSED THE END DATE: 

Understand issues that influence the quality of data 
SAQA US ID UNIT STANDARD TITLE
258804  Understand issues that influence the quality of data 
ORIGINATOR
SGB Geographical Information Sciences 
PRIMARY OR DELEGATED QUALITY ASSURANCE FUNCTIONARY
-  
FIELD SUBFIELD
Field 12 - Physical Planning and Construction Physical Planning, Design and Management 
ABET BAND UNIT STANDARD TYPE PRE-2009 NQF LEVEL NQF LEVEL CREDITS
Undefined  Regular  Level 7  Level TBA: Pre-2009 was L7  6 
REGISTRATION STATUS REGISTRATION START DATE REGISTRATION END DATE SAQA DECISION NUMBER
Passed the End Date -
Status was "Reregistered" 		 2018-07-01  2023-06-30  SAQA 06120/18 
LAST DATE FOR ENROLMENT LAST DATE FOR ACHIEVEMENT
2024-06-30   2027-06-30  

In all of the tables in this document, both the pre-2009 NQF Level and the NQF Level is shown. In the text (purpose statements, qualification rules, etc), any references to NQF Levels are to the pre-2009 levels unless specifically stated otherwise.  

This unit standard does not replace any other unit standard and is not replaced by any other unit standard. 

PURPOSE OF THE UNIT STANDARD 
This unit standard is useful for people who aim to achieve career advancement in the GIS field and provides them with essential knowledge about data quality.

A person credited with this unit standard is able to:
  • Understand and explain spatial accuracy in GIS data capture.
  • Understand and explain temporal issues in spatial data sets.
  • Analyse the classification accuracy of a dataset.
  • The interaction of errors are understood and explained in relation to multiple, integrated datasets.

    Specific range statements are provided in the body of the unit standard where they apply to particular specific outcomes or assessment criteria. 
    		•

    LEARNING ASSUMED TO BE IN PLACE AND RECOGNITION OF PRIOR LEARNING 
    The credit calculation is based on the assumption that learners are already competent in terms of the following outcomes or areas of learning when starting to learn towards this unit standard:
  • Understand data quality and metadata.
  • Interpret geo-information.
  • All fieldwork unit standards.
  • All projections related unit standards that form part of this course. 
    		•

    UNIT STANDARD RANGE 
    Range statements are included with specific outcomes as necessary. 

    Specific Outcomes and Assessment Criteria: 

    SPECIFIC OUTCOME 1 
    Understand and explain spatial accuracy in GIS data capture. 

    ASSESSMENT CRITERIA     

    ASSESSMENT CRITERION 1 
    Positional accuracy is understood and explained in terms of spatial data quality. 
    ASSESSMENT CRITERION RANGE 
    Including but not limited to:
  • Precision, scale, resolution, error measures, and tolerances.
     
    		•

    ASSESSMENT CRITERION 2 
    Logical consistency is understood and explained in terms of data quality. 
    ASSESSMENT CRITERION RANGE 
    Including but not limited to topology, slivers and organisational rules.
     

    ASSESSMENT CRITERION 3 
    Spatial accuracy is understood and explained in terms of applied national survey standards. 
    ASSESSMENT CRITERION RANGE 
    Including but not limited to tolerances, units and methodologies.
     

    ASSESSMENT CRITERION 4 
    Spatial accuracy is understood and explained in terms of different geodetic frameworks. 
    ASSESSMENT CRITERION RANGE 
    Including but not limited to Clarke-1880, WGS84, Hartebeesthoek, AFREF.
     

    ASSESSMENT CRITERION 5 
    Spatial accuracy is understood and explained in terms of its relation to the national legal survey framework. 
    ASSESSMENT CRITERION RANGE 
    Including but not limited to GIS results in relation to information on legal general plans and diagrams.
     

    ASSESSMENT CRITERION 6 
    Spatial accuracy is understood and explained in terms of completeness of the geospatial data set. 
    ASSESSMENT CRITERION RANGE 
    Wall-to-wall datasets.
     

    SPECIFIC OUTCOME 2 
    Understand and explain temporal issues in spatial data sets. 

    ASSESSMENT CRITERIA     

    ASSESSMENT CRITERION 1 
    The completeness of a geospatial dataset is understood and explained in relation to changes in the real world. 
    ASSESSMENT CRITERION RANGE 
    Changes will include, but not be limited to:
  • Changes in spatial boundaries.
  • Attribute values.
     
    		•

    ASSESSMENT CRITERION 2 
    The currentness of a dataset is understood and explained in relation to changes in the real world. 
    ASSESSMENT CRITERION RANGE 
    Data age versus accuracy.
     

    ASSESSMENT CRITERION 3 
    The problem of modelling spatial issues is understood and explained in relation to change over time. 

    SPECIFIC OUTCOME 3 
    Analyse the classification accuracy of a dataset. 

    ASSESSMENT CRITERIA     

    ASSESSMENT CRITERION 1 
    The problem of integrating multiple datasets is understood and explained in the context of the following range statement. 
    ASSESSMENT CRITERION RANGE 
    Including but not limited to:
  • Comparisons of original classification methodologies.
  • Differences in scales of measure utilised.
     
    		•

    ASSESSMENT CRITERION 2 
    Classification methodologies as used in capturing attribute data is critically assessed in the context of the following range statement. 
    ASSESSMENT CRITERION RANGE 
    Including but not limited to:
  • Nominal and quantitative classification methods.
  • Classification error matrix.
  • Scales of measure (Nominal, Ordinal, Interval and Ratio).
     
    		•

    ASSESSMENT CRITERION 3 
    Classification methodologies as used in capturing spatial data is critically assessed in the context of the following range statement. 
    ASSESSMENT CRITERION RANGE 
    Including but not limited to:
  • Nominal and quantitative classification methods.
  • Classification schemas.
  • Classification error matrix.
     
    		•

    ASSESSMENT CRITERION 4 
    The issues of classification accuracy and uncertainty is understood and explained. 

    SPECIFIC OUTCOME 4 
    Understand and explain the non-quantitative elements of geospatial data quality and the interaction of errors in relation to multiple, integrated datasets. 

    ASSESSMENT CRITERIA     

    ASSESSMENT CRITERION 1 
    Linage of a data set is described as a component given in a data quality statement in the context of the history of a data set. 

    ASSESSMENT CRITERION 2 
    Usage of a data set is descibed in the context of the applications for which the geospatial data is to be used. 

    ASSESSMENT CRITERION 3 
    Pupose of a data set is decribed in the context of the rationale for creating a data set and the information it contain as to its actual use. 

    ASSESSMENT CRITERION 4 
    Error tracking and modelling methods are used to assess quality of integrated datasets. 

    ASSESSMENT CRITERION 5 
    Weakest link hypotheses versus weighting methods are used to assess quality of integrated datasets. 


    UNIT STANDARD ACCREDITATION AND MODERATION OPTIONS 
  • Anyone assessing a learner against this unit standard must be registered as an assessor with the relevant ETQA.
  • Any institution offering learning that will enable achievement of this unit standard must be accredited as a provider through the relevant ETQA by SAQA.
  • Moderation of assessment will be overseen by the relevant ETQA according to the moderation guidelines and the agreed ETQA procedures. 
    		•

    UNIT STANDARD ESSENTIAL EMBEDDED KNOWLEDGE 
    Essential embedded knowledge is dealt with under the specific outcomes section where "Demonstrate KNOWLEDGE and UNDERSTANDING" is required. 

    UNIT STANDARD DEVELOPMENTAL OUTCOME 
    N/A 

    UNIT STANDARD LINKAGES 
    N/A 


    Critical Cross-field Outcomes (CCFO): 

    UNIT STANDARD CCFO IDENTIFYING 
    Solve problems. 

    UNIT STANDARD CCFO WORKING 
    Work effectively with others as a member of a team/group/organisation or community. 

    UNIT STANDARD CCFO ORGANISING 
    Organise and manage oneself and one`s activities responsibly and effectively. 

    UNIT STANDARD CCFO COLLECTING 
    Collect, organise and critically evaluate information. 

    UNIT STANDARD CCFO COMMUNICATING 
    Communicate effectively using visual, mathematics and language skills in the modes of oral and written presentations. 

    UNIT STANDARD CCFO SCIENCE 
    Use science and technology effectively and critically (showing responsibility towards the environment and health of others). 

    UNIT STANDARD CCFO DEMONSTRATING 
    Display an understanding of the world as a set of related systems. 

    UNIT STANDARD CCFO CONTRIBUTING 
    Contribute to the full development of each learner and the social and economic development of society at large. 

    UNIT STANDARD ASSESSOR CRITERIA 
    N/A 

    REREGISTRATION HISTORY 
    As per the SAQA Board decision/s at that time, this unit standard was Reregistered in 2012; 2015. 

    UNIT STANDARD NOTES 
    Terminology:

    Metadata:
  • Metadata refers to data describing a particular data set. In GIS this includes for example information about the lineage, projection, accuracy and precision of the dataset.

    Lineage:
  • The history or ancestry of a dataset describing the origin of the data set and the processes through which it was derived from that origin.

    Logical consistency:
  • Logical consistency usually refers to the internal consistency of the data structure and often applies to topological consistency.

    Completeness:
  • Completeness refers to the number of records in a GIS spatial layer or database table in relation to the number of feature instances in the real world. This is often a product of the currentness of a dataset.

    Attribute accuracy:
  • Attribute accuracy refers to the comparison of the closeness of attribute values to their true value in the real world.

    Positional accuracy:
  • Positional accuracy refers to the comparison of the closeness of locational information (the coordinates in a database associated with a feature instance) to the true position of the real feature instance.

    Currentness:
  • The age of a data element in relation to the present.

    Precision: Precision can be defined as:
  • The precision (number of decimals) with which a value is expressed or recorded.
  • The units of the least significant digit of a measurement; for example, if a measurement is 17.130 meters then its precision is millimetres (one unit in the last place, or ulp, is 1 mm).

    Classification:
  • In GISc this refers to the process of reducing real world phenomena to data, spatial or attribute, in order to create a framework within which particular problems can be solved.

    Classification Accuracy:
  • Usually performed by creating a matrix that provides a comparison on a category-by-category basis of classification results vs. known reference data. Although most often used in relation to classification of remotely sensed data, the principles affect both the boundary as well as the attribute of the data capture.

    Notes to Assessors:

    Logical consistency can be used as a test for data quality. Example tests are:
  • Are all polygons properly closed.
  • Does the polygon have pseudo nodes: nodes that fall on other nodes to create duplicate segments.
  • Do any segment of a polygon cross another segment of the same polygon.

    Logical consistency can also be relevant to internal organisational business rules. Example tests are:
  • Do all the road segments break at intersections and administrative boundaries.
  • Do any erf boundaries cross over suburb boundaries.
    The range statements are important and will assist with the understanding of the requirements. 
    		•

    QUALIFICATIONS UTILISING THIS UNIT STANDARD: 
      ID QUALIFICATION TITLE PRE-2009 NQF LEVEL NQF LEVEL STATUS END DATE PRIMARY OR DELEGATED QA FUNCTIONARY
    Core  63711   Bachelor of Geographical Information Science (GISc)  Level 7  NQF Level 07  Passed the End Date -
    Status was "Reregistered"     		 2018-06-30   


    PROVIDERS CURRENTLY ACCREDITED TO OFFER THIS UNIT STANDARD: 
    This information shows the current accreditations (i.e. those not past their accreditation end dates), and is the most complete record available to SAQA as of today. Some Primary or Delegated Quality Assurance Functionaries have a lag in their recording systems for provider accreditation, in turn leading to a lag in notifying SAQA of all the providers that they have accredited to offer qualifications and unit standards, as well as any extensions to accreditation end dates. The relevant Primary or Delegated Quality Assurance Functionary should be notified if a record appears to be missing from here.
     
    NONE 


    All qualifications and part qualifications registered on the National Qualifications Framework are public property. Thus the only payment that can be made for them is for service and reproduction. It is illegal to sell this material for profit. If the material is reproduced or quoted, the South African Qualifications Authority (SAQA) should be acknowledged as the source.