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Nova Scotia's
Geographic Information
Standards
Chapter 4
Data Quality and Accuracy
(Continued)
4.10 Lineage
4.10.1 Introduction
Lineage is defined as the ability to determine the origin
of the data, methods of data capture, quality control specifications
used to validate data and ownership of the data. Stated another way
lineage is a form of metadata (data about data). It provides the client
with (1) a snapshot of the data and (2) a mechanism upon which they
can place confidence in the data. Costs associated with providing lineage
information is directly proportional to the level of detail being tagged
with such information. Three levels of detail have been identified as
requiring lineage information:
the data set or map sheet level
-- next to the overall database which houses
each data set, this level is the highest. At this level, some systems
accommodate lineage documentation functionality within map headers or
provide ties to textual files.
the feature or theme level
--
each data set may be made up of a number of
themes and in each instances the method of collection, date of
collection, etc., can be different. Some systems will allow theme
tagging via the use of source identifiers, while others require such
tagging in attribute databases.
the entity or element level
-- this is the lowest level of detail presently
addressed by the standards process as part of lineage tagging. Here
all points, lines and area features would be focused upon. For example,
whether there are 2 or 22 roads in a given file, each road (or segment
of road) would be tagged with a standard set of lineage data.
In the following sections, guidelines and standards will be outlined for documenting lineage at a
variety of levels of detail. Because different GIS systems are able to handle lineage differently
(based partially upon their specific data model), it is not the purpose of this material to outline
implementation methodology.
4.11 Topic: Element Level Lineage
4.11.1 Purpose:
To provide a mechanism for data consumers to determine their own confidence levels in any data
element they are interested in, or are presently applying.
4.11.2 Background
During the 1995 Data Quality and Accuracy workshop focus group, discussions regarding lineage
were informative. Participants were asked to list items they believed were pertinent to a lineage
document. They were also asked at what level they would like to see lineage information. In the
case of the later question, an overwhelming consensus was that the element level is the objective
to which data producers should strive. Their recommendations were not without a caveat that
recognized such data collection as very costly. And while it was not the purpose of the workshop
to flush out partnerships and or client willingness to pay, there was a sense that the data
consumers might be willing to pay extra for data they had more confidence in.
4.11.3 Guideline: Element Level Lineage Tagging
Individual elements within a theme may be collected and maintained at different levels, using
different techniques, etc.. Data providers should consider tagging these elements with standard
lineage information. Such an approach will give the client a very good picture of the quality of
the specific data they are working with.
4.11.4 Standard: Element Level Lineage Information
The following lineage information must be collected at the element level (to assist in the
collection of this material a sample questionnaire is also provided):
Critical Dates:
- date of collection
- data of last update
Critical Sources:
- coordinate system used
- method of manipulation (indicating
digital format conversions where applicable)
- source of data
- method of data input
- agency of collection
- agency of ownership
- specifications used to compile
element
- revision history
- does this element meet or exceed
provincial standards
Descriptive Details:
- level of topology
- method of manipulation (indicating resident digital format)
Chapter 4 continued -
[Sections 4.0 to 4.3] [Sections
4.4 to 4.7] [Sections 4.8 to 4.9]
[Sections 4.12 to 4.16]
[Sections 4.17 to 4.19]
 Chapter Four Table of Contents
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