Features

Most items within the Queensland’s Digital Topographic Data are known as features. Features are objects of the real-world with a spatial and geographical component.

Feature Class

A "feature class" is a fundamental concept used to organize and manage geographic data. Feature classes are part of the geodatabase structure and represent a collection of geographic features with the same geometry type (point, line, or polygon) and the same attribute schema.

A feature class is a collection of feature types. A feature class can consist of a single feature type or multiple feature types. Metadata at the feature class level describes the accuracy of the data and where that data was obtained from: that is, the lineage of the data. Feature classes can also be known as datasets.

Derived Datasets

A derived dataset is a subset of a larger dataset. The purpose of these derived datasets is more efficient and focused datasets for specific needs e.g., emergency services for disaster management without the need to duplicate capture and maintenance in multiple datasets. They are also viewed/portrayed as a feature class.

Within the Topographic Data, the following datasets are derived datasets:

Feature Structure

In the vector data model, spatial features are represented as discrete geometric objects. These objects include points, lines, and polygons.

Point Features: Represent singular, discrete geographic locations, or objects, encompassing specific landmarks like population centres, wells, tourist points, helipads, or monitoring stations. Point features are typically defined by a single set of x, y (and optionally, z) coordinates.
Line Features: Portray linear or one-dimensional geographic elements such as railways, rivers, pipelines, or coastline. These features are characterized by a sequence of interconnected points.
Polygon Feature: Capture areas or regions on the Earth's surface enclosed by one or more closed boundaries. Examples include land parcels, built-up areas and islands. Polygons are typically defined by a series of interconnected points, forming a closed shape.
Multi-part Features: Constitute a distinct category capable of representing intricate or multipart geometries. They involve multiple interconnected points, lines, or polygons. For instance, a multi-part polygon might symbolize an island group, where each island serves as a component of the entire feature.

Feature Geometry

All features are defined spatially by their geometry type and vector coordinates. The following geometry types are supported.

Points - Defines point features or area features represented by a point that are displayed in mapping processes by a symbol.
Multi-points that are two or more points that are treated as one feature are supported.
Line/Polylines - A chain consisting of a sequence of non-intersecting line segments. A vertex is a change in direction along the length of a line segment or at the end of the line string.
Multi-polylines are two or more polylines, not adjoining each other and treated as one feature.
Polygons - A bounded continuous region consisting of an interior area.
Area-connected planar polygon with one external boundary are polygons that do not completely cover the interior area of the polygon. A void area within the polygon is not part of the same feature.
Multi-polygons are two or more polygons, not adjoining each other and treated as one feature. Multi-polygons can consist of polygons and holey polygons together.

All polygon boundaries must be closed.
Polygon features may contain an inner set of holes or voids that can be assigned to any feature class. For example, a Lake may have in the middle of it an area of dry land (terrestrial island).