Building a 1” DEM for Australia Dr David Lemon Research Stream Leader – Water Informatics September 2008 Water for a Healthy Country

Insert presentation title Introduction to geography of Australia

Insert presentation title Over-allocation to Irrigation Bushfire Recovery Impacts Expanding Plantations Drying & Warming Climate Uncapped Groundwater Extraction Expanding Farm Dams Growing Urban DemandThe Environmental Flows Imperative Water scarcity: A deepening problem. 8 Water Scarcity Factors

Insert presentation title Options for a new National DEM The 9 second (250 m) DEM is the only national bare-earth DEM Does not meet requirements ALOS PRISM/PALSAR 5-10m postings & 3-10m Z (DTED2.5) Requires large investment in photogrammetry SPOT HRS 20m postings 10-15m Z (DTED2) COTS solution Requires large investment in data and photogrammetry for DEM SRTM DTED2 a significant improvement on DTED1 Existing Regional DEMs and Elevation data Not a national coverage

Insert presentation title Options for the New National DEM SRTM SRTM DTED2 (1sec) will open up the interior of Australia There is information on landscape structure never seen before Significant advancement on current 9sec DEM Work on 3sec SRTM has proven problematic and would require enormous investment in manual editing SRTM DTED2 has proven to be more suited to automatic artefact and vegetation removal. Moving from 3 second to 1 second takes us beyond a visually attractive product to one that is usable for serious quantitative purposes Major investment will still be required in manual editing and data integration All other options are very expensive Likely to be made obsolete by new data sources within 5 years STRM DTED2 (1sec) offers the the most consistent and cost-effective platform for the next National DEM 9sec DEM 1sec SRTM DEM

Insert presentation title Effects of different DEM types and resolutions 9 secondSRTM 3 secondSRTM 1 secondRegional 25 mLidar 5 m

Insert presentation title SRTM and 9 second in the arid zone

Insert presentation title SRTM cleanup

Insert presentation title Processing steps Fourier transform filtering to remove systematic stripes (sensor artifacts) Removal of vegetation offsets Identification of affected areas using vegetation mapping from remote sensing and direct detection from DEM Measurement of vegetation height offset and construction of vegetation height surface Removal of height offset in affected areas 1 second data greatly facilitates this process Adaptive smoothing to reduce random height variations in flatter areas Drainage enforcement with ANUDEM using mapped streams Quality assurance yet to be performed Manual intervention will be required in some areas

Insert presentation title Fourier filtering for de-striping This is one of the worst affected areas on all of Australia, but the artefact in a subtler form is widespread Not yet fully optimised – some stripes remain

Insert presentation title Vegetation detection

Insert presentation title Vegetation offset removal

Insert presentation title Adaptive smoothing

Insert presentation title Drainage enforcement

Insert presentation title SRTM 1  contribution to catchment delineation km

Insert presentation title Key advantages of 1 second data Cleanup of SRTM data is much easier and much more effective using the 1 second data 3 second data blurs the edges we need to identify for vegetation removal Released product ideally based on 1 second, not 3 second Quantitative analysis demands better than 3 second data Representing surface shape Capturing correlations with soil properties Matching natural and constructed features in the landscape

Insert presentation title Summary SRTM cleanup process is operational Room for improvement, development is continuing 1 second data provides much better basis for veg removal QA and correction will be required before release Currently scoping effort required Cleaned SRTM without drainage enforcement can provide a useful DEM for non-hydrological purposes Vegetation height information as a byproduct With appropriate stream data SRTM can construct the geospatial fabric for water resource management, in combination with other DEMs as necessary Release of SRTM 1 second data would enable a host of applications that are not possible with pre-SRTM data and have limited value using 3 second SRTM

Thank you CSIRO Land and Water Dr David Lemon Research Stream Leader – Water Informatics Phone: Web: Contact Us Phone: or Web: