Nova Scotia's
    Geographic Information
    Standards

6.0 Introduction

Feature definition and coding is concerned with the formation and description of features in the data contained in a Provincial Land Information Management System. The code itself is unique to each feature class identified in that system.

In order for corporate information to maintain integrity from one agency to another, the consumer must have a level of confidence that if they take information from a variety of sources, the features contained in each will be unique. In this chapter, the mechanisms for establishing a feature code and the rationale behind the structure of feature codes, within the primary databases, are outlined. In addition, Appendix B supplies the consumer with a Feature Dictionary. This dictionary outlines the various features and associated codes found in the primary databases.

6.1 Topic: Framework and process for establishment of Feature Classifications

6.1.1 Background:

Historically whenever a new feature was required, a code was selected and immediately incorporated into the database. In some cases these features and associated codes have not been rationalized. As a result the potential has existed that more than one agency will have the same feature code for different features. As consumers of the information begin to access these varied data sets, conflicts arise and the consumer finds themselves having to "clean" the data before they can use it. To help prevent potential conflicts between databases, a process has been outlined for the establishment of feature definitions and feature codes.

6.1.2 Process:

When a person or agency wishes to have a feature definition or feature code considered for implementation within the primary or thematic databases the following action must be taken -

1. Contact the Department of Municipal Affairs, Land Information Management Services Division (Land Information Analyst), to determine the appropriate action necessary for the requested definition and/or code.
   
2. In consultation with the Land Information Analyst determine who, if any, are the other agencies to be affected by the request.
   
3. Consult agencies affected by the request and arrive at an interim solution.
   
4. The agency making the request must then supply a written submission of their request via the "Request for Establishment and/or Modification of Nova Scotia Land Information Standards" form. In the submission indication must be given as to the nature of the request, such that, is an existing feature definition or code inappropriate or is a new feature definition and code required for a particular purpose. Indicating also any interim actions taken.
   
5. If a feature code or definition is developed it must be forward to the Nova Scotia Committee on Standards for Geographic Information for final approval.

6.2 Feature Classification - Rationale

Within the concept of the Provincial Land Information Management System corporate land and water information will be shared. As well, the Provincial Land Information Management System can be viewed as containing primary and thematic databases. This section of the Manual describes how land and water information, as they pertain to the primary databases [Endnote 1], are classified. Information related to the thematic databases should be described by the database creator. The names and custodians of these databases appear in the "Nova Scotia Directory of Geographic Data and Information" [Endnote 2] and may be obtained by contacting NSGC - Amherst, Client Services Section. Information features that appear in the thematic databases should conform to the classification specifications described in this section.

The system adopted by the Province of Nova Scotia has been prepared by the Feature Definition and Coding Task Group under the Nova Scotia Committee on Standards for Geographic Information. Where possible, existing definition and coding systems have been adopted, for example adopting a large portion of the former LRIS system. As will be noted in the following pages, the system adopted by Nova Scotia is a hierarchical approach, going from the general, to the specific. To date there are ten general classes of features. They are listed at the end of this section.

The use of a hierarchical classification system allows a structured approach in designing and maintaining a standard feature coding system. Features can be added to the standard at any hierarchical level, subject to approval by the Nova Scotia Committee on Standards for Geographic Information. In some cases, new general classes may have to be created (the top level of the hierarchy). In others, it may be desirable to add new features to an existing class(level 2); while in others, adding another level of hierarchy to an existing code may be the preferred choice. However, if a feature definition already exists, a new code should not be added.

All data collected for the primary databases have a unique feature code. This code is restricted to a length of 12 alpha/numeric characters, which are designed to work in pairs. The first two letters always refer to one of ten major categories, followed by other pairs to further define the feature. The feature codes may also have numeric attributes (at least 2) attached, to the end which provide additional information on the sub-classes of the feature.

6.2.1 Major Feature Categories:

The ten major categories of features are grouped along with their two letter code and a description of each follows:

1. Building - BL
   A generic term for any permanent roofed construction such as a house, factory, barn, etc.
   
   
2. Designated Area - DA
   An area set aside for a particular use or purpose.
   
   
3. Delimiter - DL
   A real or imaginary entity which describes limits.
   Included are boundaries and control monuments.
   
   
4. Landcover - LC
   The representation and description of the various surface characteristics of the land.
   
   
5. Hypsography - LF
   The representation and description of land forms and relief.
   
   
6. Road and Railroad - RR
   Any feature associated with a travelled way.
   
   
7. Structure - ST
   A generic term for a man made feature.
   
   
8. Utility - UT
   A public service such as gas, water, electricity, etc.
   
   
9. Hydrography - WA
   Surface water as indicated on a topo map and related features.
   
   
10. Cadastral - CD
    

Two numeric digits define sub-classes of a feature. These sub-classes are identified in the table below. NOTE: Both columns must be filled if a sub-class from either column is used.

Once a feature has been named and defined, all information about the feature is recorded in the feature dictionary using the standard entry format.

6.2.3 Examples of Features with Numeric Attributes:

DAQU10 - Quarry / left where
- DA indicates a designated area (major category)
- QU further define the feature as a quarry
- 10 with the 1 (taken from column 1) indicating left and the 0 (taken from column 2) used as a filler

DAPA11 - Parking Area / left / paved where
- DA indicates a designated area (major category)
- PA further define the feature as a parking area
- 11 with the first 1 (taken from column 1) indicating left and the second 1 (taken from column 2) indicating the area is paved

RRBR03 - Bridge / under construction where
- RR indicates a road or railroad (major category)
- BR further define the feature as a bridge
- 03 with the 0 (taken from column 1) used as a filler and the 3 (taken from column 2) indicating that it is under construction

6.2.4 Suffix Qualifiers of Cadastral Features

Within the Primary Databases, cadastral feature have attribute suffixes which relate to the origin of its data. These suffixes have maintained the hierarchical structure of the feature code rationale but they do not appear as numeric suffixes, rather they are alphanumeric characters. Over time, these alphanumeric suffixes will be phased out and the source information will be embedded in an attribute file of the GIS. To reduce confusion in determining if the last two characters of a code relate to the suffix or not, any alphanumeric suffix is preceded by two underscore characters "_ _". Please refer to the examples provided below for additional information.

Examples of Features with Alphanumeric Attributes (Cadastral Features Only):
CDRRIB_ _GB - where
- CD indicates a cadastral feature (major category)
- RRIB_ _ further defines the feature as being a property line dividing railway right-of-way parcels.
- GB with the G (taken from column 1 - Source) indicating the source of the property line being a survey plan and the B (taken from column 2 - Further Information) indicating the property line not being tied to control.

CDPL_ _FA - where
- CD indicates a cadastral feature (major category)
- PL_ _ further defines the feature as being a property line dividing freehold parcels.
- FA with the F (taken from column 1 - Source) indicating the source of the information as a Deed and the A (taken from column 2 - Further Information) indicating the information was taken from a Coordinated Survey.

6.3 Feature Code Data Entry Form (with associated glossary)

In the following two sbsections the reader is provided with a standard form which may be used to compile a feature dictionary along with a brief description of what is being colelcted in each part of that form. Readers accessing this manual electronically may obtain a skelaton copy of a database housing a feature dictionary. They will also be able to obtain an electronic version of the questionnaire.

6.3.1 Entry Form Content Requirements

This section provides the reader with a brief description of the material being collected on the feature coding form.

Feature Name and Feature Definition:
Maximum of three sentences defining the feature in non-technical terminology. Include a cross reference, where appropriate, to other features which may be equivalent.

Orginating Organization:
The name of the Branch, department, organization, etc. which has defined this particular feature.

Descriptors:

Feature Code: To be assigned by the Department of Municipal Affairs, Land Information Services Division. (May be in consultation with agency making feature request.)

Feature Code Suffixes:
The last two numeric digits of the feature code are held open to further define sub-classes of the feature. For example PPXXXXXXXXnn where PP represents the primary category for the feature in question, XXXXXXXX is the additional feature code and nn are two numbers from 0-9 corresponding to the feature code sub-class (or suffix). If the feature codes is for cadastral data, the suffix is alphanumeric and the two characters are preceeded by two underscore characters. (Please refer to the section entitled "Feature Classification Rationale" for suffix values and represented features.)

Other:

NTDB / Other Feature Code(s):
The feature code(s) used by other organizations (for example, Federal Government departments or international associations) to describe this same feature. Should only be used as a cross-reference aid.

Representation:

Map Series :
The features being presented in the feature dictionary may be scale dependent. This section provides the user ofthe feature dictionary with an indication of the scale dependency of the feature.

Minimum Size (metres):
The minimum size of the entity depending on whether it is to be represented geometrically as a point, line or area in that particular digital map series or graphical data file. "Range" is a term coined from the NTDB Manual referring to the length of the side of a square corresponding to the minimum size the feature can be for entity representation. For inclusion in the file, the features width must be greater than half the "range" value. For example a feature may have a "range" value of 100. That being the case, the minimum size the feature can be is 100 squared. However, one final check must be made to determine if a feature is represented. If the width of the feature is greater than 50 (in this case) then it is representable.

Explanatory Notes and Diagrams (optional):

Explanatory Notes:
These notes are to be of a non-technical nature and may include the process by which the feature is collected. For example point-by-point versus stream mode digitizing, generated from digital terrain models, photogrammetric compilation, survey plan source, etc.

Diagrams:
Where appropriate, examples may be supplied to enable the user to better appreciate the features representation.

Chapter 6 (continued) -
[Feature Code Index - A to K]
[Feature Code Index - L to Z]

Endnotes: 1. The primary databases, otherwise referred to as the Primary Databases of the Provincial Land Information Management System, is comprised of layers of aerial photographic data, control survey (coordinate framework) data, topographic mapping (LRIS urban and resource series) data, and property mapping (cadastral overlay) data. All thematic databases within the provincial system must reference their land related information to the primary databases.

2. The "Nova Scotia Directory of Geographic Data and Information - 2nd Edition" was produced in June 1995.

Chapter Six Table of Contents