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3 second SRTM Derived Smoothed Digital Elevation Model (DEM-S) Version 1.0

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: ANZCW0703014217

Title: 3 second SRTM Derived Smoothed Digital Elevation Model (DEM-S) Version 1.0


Custodian

Custodian: Geoscience Australia

Jurisdiction: Australia


Description

Abstract:

The 3 second (~90m) Smoothed Digital Elevation Model (DEM-S) Version 1.0 was derived from resampling the 1 second SRTM derived DEM-S (gridded smoothed digital elevation model; ANZCW0703014016). The DEM represents ground surface topography, excluding vegetation features, and has been smoothed to reduce noise and improve the representation of surface shape. The DEM-S was derived from the 1 second Digital Surface Model (DSM; ANZCW0703013336) and the Digital Elevation Model Version 1.0 (DEM; ANZCW0703013355) by an adaptive smoothing process that applies more smoothing in flatter areas than hilly areas, and more smoothing in noisier areas than in less noisy areas. This DEM-S supports calculation of local terrain shape attributes such as slope, aspect and curvatures that could not be reliably derived from the unsmoothed 1 second DEM because of noise. A full description of the methods is in progress (Gallant et al., in prep) and in the 1 second User Guide. The 3 second DEM was produced for use by government and the public under Creative Commons attribution.

The 1 second DSM and DEM that forms the basis of the product are also available as 3 second products (DSM; ANZCW0703014216, DEM; ANZCW0703014182, DEM-S; ANZCW0703014217).

ANZLIC search words:

  • CLIMATE AND WEATHER Climate change
  • ECOLOGY Landscape
  • HAZARDS Flood
  • LAND Topography
  • PHOTOGRAPHY AND IMAGERY Remote Sensing

Spatial domain:

locality map

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

Geographic extent polygon: 113 -10, 154 -10, 154 -44, 113 -44, 113 -10,

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

Geographic bounding box:
North bounding latitude: -10 °
South bounding latitude: -44 °
East bounding longitude: 154 °
West bounding longitude: 113 °

Data currency

Beginning date: 2000-02-11

Ending date: 2000-02-22


Dataset status

Progress: In Progress

Maintenance and update frequency: Not Known


Access

Stored data format:
DIGITAL - ArcGIS-grid ArcInfo grid
Available format type:
DIGITAL - ArcGIS-grid ArcInfo grid

Access constraints:

This material is released under the Creative Commons Attribution 3.0 Australia Licence.

Further information on Creative Commons can be found on the website http://creativecommons.org/licenses/by/3.0/au/

Free Data Download

Data quality

Lineage:

The horizontal positional error is estimated to be three times that of the 1 second products. The 1 second products are the same as the raw SRTM 1 second data, with 90% of tested locations within 7.2 m for Australia. See Rodriguez et al. (2006) for more information on SRTM accuracy.

Positional accuracy:

Accuracy of the 3 second DEM-S was tested using the same 1198 PSM as the 1 second DEM accuracy assessment. Results of the comparison showed the absolute accuracy of the data as tested relative to AHD71 to be 14.54m at the 95th percentile with an RMS error of 7.029m in open, flat terrain. 99 percent of points are within a height difference of less than 29.97m.

Relative elevation accuracy between adjacent cells is improved in the DEM-S due to the reduction in noise levels; this has not been quantified but is evident in the comparison of slopes calculated before and after smoothing as shown in the User Guide (Geoscience Australia and CSIRO Land & Water, 2010). The smoothing process estimated the typical improvements in the order of 2-3m in the 1 second DEM-S.

Height accuracy is likely to be poorer in areas where voids have been filled using the 9 second DEM, particularly in high relief areas.

Attribute accuracy:

not known

Logical Consistency:

The 1 second DEM-S represents ground elevation with greatly improved relative elevations between adjacent grid cells in low relief areas due to the smoothing process. Slopes as small as 0.02% (2 m in 10 km) can be resolved in the DEM-S.

The removal of vegetation involves estimation of vegetation height at the edges of vegetation patches, and interpolation of those heights across areas of continuous vegetation cover. Variations in vegetation height within large areas of vegetation are not captured by this method. The vegetation removal process guarantees that no elevations have been increased as part of the process.

All void areas have been filled and there are no discontinuities due to original tile boundaries.

The SRTM editing rules relating to water bodies have been respected in the processing: lakes are flat, rivers decline continuously in a downstream direction and sea surfaces are at 0m elevation. Flattened water bodies occupy the same areas as in the original SRTM 1 second data. Grid cells adjacent to water bodies are at least 1cm above the water surface. Void areas within water bodies (small islands not represented in the original SRTM data) are at least 1cm above the water surface over their entire area.

Completeness:

The DEM-S covers all of continental Australia and near coastal islands land areas including all islands defined by the available SRTM 1 second elevation and SRTM Water Body Data datasets. Some fragments of mainland or pieces of islands may be missing.


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/ANZCW0703014217.html

Metadata reference XML: http://www.ga.gov.au/meta/ANZCW0703014217.xml

Conversion to floating point format

The smoothing process alters all data values in the 1 second DEM by varying amounts and the result is a floating point data set capturing in some places very small but meaningful differences in elevation between adjacent cells.

Ancillary data layers

- A water mask at 1 second resolution showing the cells that are part of the flattened water bodies

- JPEG Image of the 3 second DEM-S

References

Gallant, in (in prep) An adaptive smoothing method for improving noisy DEMs.

Geoscience Australia (2008) GEODATA 9 Second DEM Version 3

Geoscience Australia and CSIRO Land & Water (2010) 1 Second SRTM-Derived Digital Elevation Model (DSM, DEM, DEM-S and DEM-H) User Guide. Version 1.0. Geoscience Australia.

Rodriguez, E., Morris, C.S., and Belz, J.E. (2006) A global assessment of the SRTM performance. Photogrammetric Engineering and Remote Sensing 72 (3), 249-260.

Slater, J.A., Garvey, G., Johnston, C., Haase, J., Heady, B., Kroenung, G., and Little, J. (2006) The SRTM data "finishing" process and products. Photogrammetric Engineering and Remote Sensing 72 (3), 237-247.

Authors:Wilson, N. Tickle, P. Gallant, J. Dowling, T. Read, A.
SPATIAL INFORMATION FOR THE NATION