Nova Scotia's
    Geographic Information
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Chapter 4
Data Quality and Accuracy

(Continued)

4.4 Topic: Standards for Digital Map Content

4.4.1 Purpose:

To provide a cross reference to items documented in the feature catalogue (see Appendix B in the Geographic Information Nova Scotia - Standards Manual).

4.4.2 Background:

Information included with a map file is compiled to given specifications. A feature may be collected as a point, line or area. Although a map scale may have certain compilation specifications, features are not always collected to the smallest level of detail. For example, some features could be collected as areas but the compilation specifications only require them to be compiled as point features.

In Chapter 6, of the Standards Manual, the standard feature coding rationale is outlined and Appendix B provides details on feature definitions, codes, etc. One item which should be highlighted in the Feature Catalogue is a table entitled "Minimum Size (meters)". This table indicates how a feature is collected at a 1:10 000 scale. In future editions of this manual additional tables will be provided to highlight the minimum size and type of feature being compiled at all base map scales.

4.4.3 Standard: Digital Map Content - 1:10 000 scale data

Adopt the map compilation specifications for "Minimum Size (in meters)" for features at a scale of 1:10 000, as is highlighted in the Standards Manual's Feature Catalogue.

4.5 Topic: CURRENCY

4.5.1 Introduction:

The basic premise behind data currency, or any data standard for that matter, is supplying the consumer with the most reliable, up to date, product possible. With the data consumer's interests in mind, issues surrounding data currency must be addressed simultaneously, for both the Primary and Thematic Databases. In the following sections a number of data currency guidelines and standards are presented.

Within a PLIMS corporate information strategy, one of the underlying philosophies in developing an effective system is that data will be collected as close to source as is possible. The reasons for such action are tangible and intangible. Source data is perceived as being the most reliable. Reliability in turn can mean wider acceptance. Wider acceptance can mean wider applications and it is the wider applications that can in turn lead to efficiencies and more cost effective decisions/programs.

4.6 Topic: Client Services - A feedback mechanism

4.6.1 Purpose:

To provide a mechanism, for both data consumers and data producers, to communicate concerns with respect to data set application(s).

4.6.2 Background:

In a 1995 survey conducted by the Data Quality and Accuracy Task Group participants were asked the following question:
      If your organization has had occasion to deal with 'dated' data did you
      (a) contact the original source indicating [sic] the currency problem;
      (b) find new sources for data;
      (c) generate your own 'updates' to suit your particular project;
      (d) live with the dated material.

While it was hopeful that the responses would be different, they were not totally surprising. More than 50% of respondents indicated selection (c) such that they would recreate data if the source data were viewed as dated (ie not current) or unreliable.

Reasons for such action can vary. In some instances individuals may not wish to go through a process of contacting the source to determine if the data they received was correct. Other times the consumer may not want to wait for an update from the source. The result however is that the source makes an assumption about their data (ie assumes that what was provided met the client's need). The client meanwhile might also assume that the source is aware of the discrepancy and that steps are being taken to rectify the problem. To prevent such assumptions a feedback mechanism is necessary. This mechanism would allow the client to formally notify the source of its concerns.

4.6.3 Guideline: Digital Geographic Data - Client Feedback Form

Data providers will provide clients with formal avenues by which they might raise concerns regarding the data. Agencies wishing to develop their own formal feedback mechanisms are encouraged to do so. A sample process is outlined below, followed by a recommended form.

Sample process
- Client receives a digital data set, along with the feedback form.
- Issues/concerns are raised during the application of the data.
- As the client identifies issues in the application of the data, they complete the necessary sections of the feedback form and relay the same to the data provider.
- Upon receipt of the feedback form the data provider notifies the client accordingly with some indication of when the issue will be addressed.
- Data provider reviews comments to determine course of action to rectify the issue(s) and notes on the form the level of priority to be placed upon same.
- Data provider contacts client with assessment of the issue and an indication of how it can be resolved.

4.7 Topic: Currency Documentation

4.7.1 Purpose:

To ensure that all corporate geographic data sets are able to be referenced by the general public and that in the referencing process, the data consumer can formulate opinions as to the data sets currency.

4.7.2 Background:

Within a provincial land information management system there are many possible methods / methodologies which might be incorporated into primary and thematic database updates. Determining the method best suited for a given agency is partly based upon anticipated application(s) of the data. On the one hand, updates may only be acceptable via traditional photogrammetric methods. Such methods provide a high level of stability in the final product and thus provide the consumer with reassurances that the data is reliable. The drawback to such updating relates to cost and as a result agencies may elect to keep their databases current via other means (for example, periodic spot checks followed by wide spread generalization based upon trends).

In instances where a database, or for that matter a file within a database, contains a variety of data layers, update methods are not necessarily consistent throughout. It is therefore not only the methodology which is of interest to the data currency issue, it is also the mechanism used to document how the data is kept current. For example, a file containing road and hydrographic detail might see the roads updated from construction plans, while the hydrographic detail is updated via photogrammetric means. Currency issues would therefore relate not only to the method of data capture but also the age of the various update methods employed (e.g. age of photography, date of stereo compilation from the photography, age of construction plans , etc)

4.7.3 Standard: Metadata documentation

In the provincial land information management system all corporate geographic data is to be accompanied by a metadata file. This file will conform to the metadata standard (as found in Chapter 10 of the "Geographic Information Nova Scotia - Standards Manual". The metadata file also contains a description of the currency of all features found in the file along with a brief description of how the features were collected. (Statistics Canada refers to such documentation as a Data Quality Report)

Chapter 4 continued -
[Sections 4.0 to 4.3]   [Sections 4.8 to 4.9]   [Sections 4.10 to 4.11]   [Sections 4.12 to 4.16]  
[Sections 4.17 to 4.19]

Chapter Four Table of Contents