How to Use MS1759?

1. Coding of features and attributes

This standard has not been developed to the requirements of any single application or level of resolution. This standard is also not meant to support any specific digital product. As with any dictionary, there may be more than one way to encode spatial entities, either by offering a choice of features or a combination of features and attributes

For example, an airport is listed as feature AB0010 - Aerodrome
(A defined area on land or water intended to be used either wholly or in part for the arrival, departure and surface movement of aircrafts, could also be coded as feature BD0010 - Institutional Building with attribute INU (Institutional Usage) with a coded value of 001 (Airport Terminal)).

The choice is entirely up to user own application and interpretation; to code only the terminal building or the entire aerodrome area. Feature codes are shown in Annex A and Attribute codes and values are given in Annex B. Annex B also provides information as to the units, formats, ranges, increments and maximum text characters typically associated with each actual value attribute.

If a feature does not reside within this standard, it is allowed for a user-designated features and associated attributes. Otherwise, features and attributes shall be encoded using this standard. The process for amending and updating this standard is described in 2.3.

2. Coding structure

2.1 Features

Each feature is identified by a unique six-character code. The first character corresponds to the feature category and can have an alphabetic value from A through Z. Currently there are twelve feature categories, including one category, X, which has been reserved for special use (dataset-specific) features.

2.2 Attributes

Attributes are used to describe characteristics of a feature. Each attribute is described by using attribute codes to represent the category of information. Attribute value format statements provide a computer interpretation for the attribute value data type (e.g. real, alphanumeric) and attribute values give quantitative/qualitative meaning to the attribute code. An attribute can be used by any feature, but care must be taken so that only meaningful attributes are chosen for a particular feature.

For example, syntactically, an attribute "Lift Facilities" can be used with feature "Rail Line", but semantically, the combination is useless. A list of possible attributes for each feature have been provided for the convenient of users.

2.2.1 Attribute codes

Each attribute is identified by a unique three character alphanumeric code. For example, the attribute "Road Service Area" has the code RDS and the attribute "Bridge Construction Material Type" has the code BMT.

2.2.2 Attribute values

There are two types of attribute values: coded and actual. A given attribute has only one type of value, which is specified in Annex B. Coded values may range from 0 to 999 and each of the value has its own meaning. Actual values are typically real measurements like height, width, date, etc. The units of measurement associated with an attribute are abbreviated according to the units of measurement codes as detailed in Annex B.

2.2.3 Range value attributes

Normally attributes are single valued text strings, numbers or enumerated values. However, at times it is necessary to assign values that fall within predetermined ranges. This can be done through an enumerated list that pre-defined the permitted ranges.

2.3. Rules for documenting new features and attributes

This standard should be used during the development of specifications of digital application systems to support and satisfy the exchange of spatial information. However, this standard can be modified and updated in response to dynamic technology and evolving requirements. If this standard does not contain the required features, the standard allows for amendment to incorporate extensions and additions. This sub clause lists the rules that are used to document the features and attributes contained in Annexes A and B. All extensions and additions shall also follow these rules:

a) Feature and attribute names should be precise and unambiguous;

b) Attribute values should be self-describing;

c) A feature and attribute should not have the same name;

d) A feature or attribute can have multiple names but only one definition;

e) A feature or attribute name should not be used in the description of the feature or attributes;

f) A feature name or definition should not specify if the feature is an area, point or line feature;

g) A feature should be relatively permanent;

h) A feature should not be duplicated between categories;

i) All attribute values are positive unless otherwise stated;

j) A boundary is just a spatial object or information that be considered a line feature and not a perimeter or solid surface of an area or spatial feature;

k) The systematic structure of the coding schema should be permanent.

The features and attributes in this standard represent both spatial information and information which is considered important in geographic information system. Care should be taken to restrict additions to this standard to items of a stable nature only. Users should, for the development of their feature and attribute requirements, seek inter-organisation co-operation and co-ordination.