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GEODATA 9 Second Digital Elevation Model (DEM-9S) Version 3

Note: This metadata describes the dataset in accordance with the ANZLIC (Australia New Zealand Land Information Council) Core Metadata Guidelines Version 2.


Dataset citation

ANZLIC unique identifier: ANZCW0703011541

Title: GEODATA 9 Second Digital Elevation Model (DEM-9S) Version 3


Custodian

Custodian: Geoscience Australia

Jurisdiction: Australia


Description

Abstract:

The GEODATA 9 Second DEM Version 3 is a gridded digital elevation model computed, using the ANUDEM elevation gridding program Version 5.2.2, from continent-wide topographic data including point elevations, streamlines, water body boundaries and cliff lines. The grid spacing is 9 seconds in longitude and latitude (approximately 250 metres). The 9 Second DEM is a cooperative effort of the Fenner School of Environment and Society of the Australian National University and Geoscience Australia.

ANZLIC search words:

  • LAND Topography Models

Spatial domain:

locality map

Geographic extent name: AUSTRALIA EXCLUDING EXTERNAL TERRITORIES - AUS - Australia - Australia

Geographic extent polygon: 112 -9, 154 -9, 154 -44, 112 -44, 112 -9,

Note: The format for each Geographic extent name is: Name - Identifier - Category - Jurisdiction (as appropriate) See GEN Register

Geographic bounding box:
North bounding latitude: -9 °
South bounding latitude: -44 °
East bounding longitude: 154 °
West bounding longitude: 112 °

Data currency

Beginning date: 2005-07-01

Ending date: 2008-06-30


Dataset status

Progress: Complete

Maintenance and update frequency: Not Known


Access

Stored data format:
DIGITAL - img ERDAS Imagine image Imagine Geographic GDA94
DIGITAL - asc ASCII text Geographic GDA94
DIGITAL - ArcGIS-grid ArcInfo grid Geographic GDA94
DIGITAL - ers ER Mapper raster dataset ER Mapper Geographic GDA94
Available format type:
DIGITAL - ArcGIS-grid ArcInfo grid Geographic GDA94
DIGITAL - asc ASCII text Geographic GDA94
DIGITAL - img ERDAS Imagine image Imagine Geographic GDA94
DIGITAL - ers ER Mapper raster dataset ER Mapper Geographic GDA94

Access constraints:

The data are subject to Commonwealth of Australia Copyright. A licence agreement is required and a licence fee is also applicable for packaged data (included in the purchase price).

Free Data Download

Data quality

Lineage:

Source data used to create the GEODATA 9 Second DEM Version 3 consisted of the following datasets.

1. A total of 5.2 million spot heights from the GEODATA TOPO-250K Relief theme, Version 1.

2. A total of 2.0 million watercourse features from the drainage layer of the GEODATA TOPO-250K Hydrography theme, Version 1.

3. A total of 25,000 cliff lines from the morphology layer of the GEODATA TOPO-250K Relief theme, Version 2.

4. A total of 19,000 trigonometric data points from the National Geodetic Database.

5. Coastline data from GEODATA COAST 100K data and coastal inlets from the GEODATA TOPO-250K Framework layer.

6. Lakes from the waterbody layer of the GEODATA TOPO-250K Hydrography theme, Version 1.

7. Reservoirs from the waterbody layer of the GEODATA TOPO-250K Hydrography theme, Version 1 for Tasmania and Version 2 for the mainland.

8. Radar altimeter point elevation data supplied by Geoscience Australia for Lake Eyre.

9. A total of 326,000 spot heights digitised by ANU Fenner School from 1:100K scale topographic mapping.

10. A total of 90,000 stream arcs digitised by ANU Fenner School from 1:100K scale topographic mapping.

11. A total of 25,000 sink data points digitised by NU Fenner School from 1:100K scale topotraphic mapping.

12. A total of 4,000 coastline cliffs selected from the GEODATA COAST 100K data.

13. Selected contour lines and cliff lines digitised by ANU Fenner School from 1:100K scale topographic maping.

All data revisions were performed by the Australian National University Fenner School. These included, for Version 3, a total of 12,000 corrections to spot heights from teh GEODATA TOPO-250K Relief theme and 7,000 corrections to stream data from the GEODATA 250K Hyrdrography theme. Streamline corrections were make to orient all streams in the direction of flow. All canals were removed from the streamline data except where they were needed to assist in defining drainage structure. All points on tops of sand dunes were removed.

The DEM was calculated by ANUDEM Version 5.2.2 in overlapping tiles across Australia. The tiles corresponded apprximately to the standard 1:1M map sheet areas but with an adjoining margin of 0.1 degree (approximately 10 kms). The overlapping grid tiles were blended together using the ARC/INFO mosaic command.

ANUDEM Version 5.2.2 had the following improvements.

1. Improved automated drainage enforcement algorithm.

2. Improved representation of streamlines and cliff lines.

3. Incorporation of stream distributaries.

4. Minimisation of spurious interactions between streamlines and cliff lines and between closely separated cliff lines.

5. Improved location and representation of coastlines permitting a smooth transition to the sea floor in the absence of coastal cliffs.

6. Improved representation of lakes.

The drainage enforcement algorithm within ANUDEM was applied to the whole continent. Errors in source point and streamline data were mainly detected by examining diagnostics output by ANUDEM. These consisted of remaining spurious sinks, large residuals from point data and stream and cliff error diagnostics. Grids were finally checked by Geoscience Australia against Version 2 of teh 9 second DEM and 1:100K scale topographic mapping. If elevation or stream errors were found then corrections were made and the grid was re-calculated.

Positional accuracy:

The density of the source data and the 9 second grid spacing means that the grid can be considered to have a scale of 1:250 000. The notion of positional accuracy for the longitude and latitude values given in the data is not applicable as the grid locations are generated as part of the grid generation process.

Attribute accuracy:

The elevation given for each cell is an estimate of the elevation at the centre of the area covered by the cell. The accuracy of the elevation values can be considered as being continuously variable across the DEM, with local relief around each DEM cell, as defined by its four closest neighbours, having the greatest influence.

Estimates based on residuals from points selected from 1:25K scale contour elevation data, which were not used to calculate the DEM, indicate that 50% of the 9 second DEM has local relief not exceeding 4 metres and corresponding standard elevation error not exceeding about 10 metres. A further 30% of the DEM has local relief not exceeding 13 metres and a standard error not exceeding about 15 metres. A further 15% of the DEM has local relief not exceeding 56 metres and a standard elevation error not exceeding about 35 metres. A further 4% of the DEM has local relief not exceeding 140 metres and standard error not exceeding 50 metres. For the remaining 1% of the DEM, local relief is essentially less than about 250 metres and standard elevation error does not exceed about 60 metres.

Maximum errors are naturally greater than standard elevation errors. They range from around 20 - 40 metres in low relief areas up to around 200 - 300 metres in complex high relief areas associated with cliffs. Not all significant peaks have been included in the source data for the DEM. It shoulld therefore be used with care in line of sight applications that depend critically on the accuracy of representation of peaks.

Comparisons with 19,000 trigonometric data points from the National Geodetic Database, which were included in the source data for the DEM, confirmed a root mean residual of 12 metres at principal high points across the continent and an overall maximum error of about 200 metres.

The mean distance of the gridded stream lines, as incorporated in the 9 second DEM Version 3, from the GEODATA 250K streamline network is about 60 metres or one quarter of the width of one grid cell. Approximately 95% of the gridded streamlines lie within 125 metres of the mapped streamline network and virtually all are within 270 metres.

Logical Consistency:

The DEM supplies one elevation value for each grid cell. Each value denotes an estimate of the elevation of the mid-point of the cell. The heights of each cell and its eight immediate neighbours are such that elevations decrease in the direction of flow along all supplied data streamlines, including all supplied data stream distributaries. The elevation at each supplied sink point is a local minimum of the elevation grid.

Completeness:

The DEM covers all land areas including all islands defined by the GEODATA COAST 100K data. The source data include all corrected GEODATA TOPO-250K Version 1 spot heights, GEODATA TOPO-250K Version 1 streamlines and GEODATA TOPO-250K Version 2 cliff lines. The source data also includes all corrected trigometric points but does not include all mapped peaks at the 1:100K scale.


Contact information

Contact organisation: Commonwealth of Australia (Geoscience Australia) (GA)
Contact position: Manager Client Services
Mail address: Cnr Jerrabomberra Ave and Hindmarsh Dr
Mail address: GPO Box 378
Locality: Canberra
State: ACT
Country: Australia
Postcode: 2601
Telephone: 02 6249 9966
Facsimile: 02 6249 9960
Electronic mail address: sales@ga.gov.au

Metadata information

Metadata date: 2013-03-08


Additional metadata

Metadata reference XHTML: http://www.ga.gov.au/meta/ANZCW0703011541.html

Metadata reference XML: http://www.ga.gov.au/meta/ANZCW0703011541.xml

A national regular grid digital elevation model (DEM) of Australia with a grid spacing of 9 seconds in longitude and latitude (approx. 250m).

The DEM has a nominal scale of 1:25K and can be used for national, statewide and regional appications, particularly those that depend on an accurate respresentation of surface drainage and catchment structure.

The DEM was calculated by the ANUDEM elevation gridding program Version 5.2.2 as developed by the Australian National University Fenner School of Environment and Society.

The source data included 5.2 million point elevations, 2.0 million streamlines and 25,000 cliff lines from the GEODATA TOPO-250K data layers and 19,000 trigonometric points from the National Geodetic Database.

These source data were supplied by Geoscience Australia and were comprehensively revised by the ANU Fenner School.

The Fenner School also digitised an additional 326,000 spot heights, 90,000 streamlines, 25,000 sink points and 1,000 cliff lines from 1:100K scale mapping to improve the elevation and drainage accuracy of the DEM across the continent. The additional sink point data also permitted application of the drainage enforcement algorithm of the ANUDEM program across the entire continent. Coastline data were selected from GEODATA COAST-100K data and the GEODATA TOPO-250K framework layer. Streamines and cliff lines were incorporated to better represent shape and drainage structure. The ANUDEM program was revised to improve the representation of streamlines, cliff lines, lake boundaries and the coastline.

The program was also revised to systematically represent streamline distributaries, and to minimise spurious interactions between cliffs and streamines and between closely separated cliff lines.

It was also revised to provide improved diagnostics to identify a wide range of errors in all source data. All errors detected in the source data were corrected. Final DEM quality checking was performed by Geoscience Australia in consultation with the ANU Fenner School.

For further Information, refer to the GEODATA 9 Second DEM Version 3 and Flow Direction Grid User Guide (UserGuide.pdf), supplied with the product or available on www.ga.gov.au

For further information on the ANUDEM program Version 5.2.2 used to calculate the DEM please contact the Fenner School of Environment and Society:

Fenner School Publications/Software

Fenner School of Environment and Society

Australian National University

CANBERRA ACT 0200

e-mail: publications@fennerschool.anu.edu.au

Internet: http://fennerschool.anu.edu.au/publications/software/

Authors:Hutchinson, M.F. Stein, J.A. Stein, J.L.
SPATIAL INFORMATION FOR THE NATION