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Topographic (GIS) Data
Digital spatial data, or Geographic Information System (GIS) data, is a digital representation of the real world and spatial objects such as points, lines and polygons are used to depict spatial features.
- Points are used to depict point features such as buildings or locations;
- Lines are used to depict linear features such as roads or drainage; and
- Polygons are used to depict area features such as waterbodies or parks.
The spatial objects are linked to attributes that describe the features and phenomena that exist at those locations.
Topographic Data
Topographic data depict the natural and constructed features on the Earth's surface and is generally reflective of the features on the related scale topographic map.
Geoscience Australia's topographic data is available in the following scales which reflect their level of accuracy and best scale for use. The smaller the scale is (i.e. 1:250 000 is a smaller scale than 1:100 000), the less features are depicted in the data and the less accurate they are. This is because different applications of data require different scales and complexity of feature depiction. For instance:
- 1:100 000: At this scale 1 centimeter (cm) is equal to 1 kilometre (km). This is the largest scale data provided by Geoscience Australia and is particularly suited for land management and planning applications. Data quality and reliability varies at this scale
- 1:250 000: At this scale 1 cm is equal to 2.5 km. The data has been prepared to provide high quality base information for mapping and GIS professionals as it provides a detailed overview over a large area
- 1:1 million: At this scale 1 cm is equal to 10 km. This data covers the Australian landmass and its island territories and was created by generalising Geoscience Australia's 1:250,000 topographic data.
- 1:2.5 million: At this scale 1 cm is equal to 25 km. This data is a vector representation of Geoscience Australia's 1:2.5 million scale general reference map and is suited to regional, state-wide or national applications.
- 1:5 million: At this scale 1 cm is equal to 50 km. This data is a vector representation of Geoscience Australia's 1:5 million scale general reference map and is suited to larger regional, state-wide or national application.
- 1:10 million: At this scale 1 cm is equal to 100 km. This data has mainly been derived from Geoscience Australia's 1:250,000 topographic data and is suited to state-wide or national applications.
GEODATA
GEODATA is Geoscience Australia's range of digital data products designed specifically for use in geographic information systems (GIS). The following scales of topographic data are part of the GEODATA range: 1:100 000 for the ACT Region; 1:250 000; 1:2.5 million; 1:5 million; and 1:10 million.
While GEODATA are designed for use in GIS, for such applications as polygon overlay and network analysis, they are flexible enough to be transformed into other formats to allow their use in computer aided drafting (CAD) packages, non-graphic databases and spreadsheet applications.
All GEODATA products are:
- GIS Compatible: Every GEODATA product is designed to be immediately useful within GIS. You save the expense of bringing the data up to standard. For vector products, this means the adoption of a suitable data model and exacting standards for topological integrity;
- Nationally Consistent: Each GEODATA product adheres to a consistent, national specification. As a consequence, each product offers consistency in the treatment of features and attributes, the criteria for feature selection, the positional and attribute accuracy, and the data point density;
- Quality: All products undergo tests on vital aspects such as topological integrity, completeness, and positional and attribute accuracy;
- Comprehensively Documented: Comprehensive documentation accompanies all GEODATA products, allowing you to determine whether a particular product is suitable for your application and to ensure you realise maximum value from the data.
- Regularly Maintained: Through timely revisions and upgrades, GEODATA products generally are up-to-date and relevant to changing customer requirements.
Other Data Products
Geoscience Australia began capturing digital map data in the early 1970's, primarily for map production purposes. These data have a structure and graphical accuracy well suited to the reproduction of maps at the same or smaller scales to the source material. However, the data may vary greatly in quality depending on the method of capture and digitising specifications in place at the time of capture. These data are best suited to graphical applications.
Products not complying with the GEODATA standard use the geometric objects of points and lines to provide map detail. Points are used to depict point map features or symbols, while lines are used to depict linear features such as roads and rivers or to delimit the boundaries of area features such as lakes and large buildings. The cartographic feature represented by the point or line is given by a feature code.
This "map data" are most suitable for use as a graphical backdrop but they can be used for more sophisticated GIS applications after some restructuring by the user. Such products include the non-GEODATA 1:100 000 data and various thematic data.
