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4. SIC_253_georectification

Description

The orthorectification of the QuickBird image (17 January 2003, SIC 253) was done as part of the Heard Island AAS2939 project (Lucieer et al. in Jan - June 2008). This QuickBird image was orthorectified and co-registered to the IKONOS Jan. 2004 image (metadata ID: SIC_266_267_georectification). All processing was done in ENVI 4.4 (https://esriaustralia.com.au/envi).

Quality

The processing done on the image was:

Pansharpening

- The original Jan 2003 panchromatic band was used to pansharpen the original multispectral image. A discrete wavelet transform (DWT) was used. A wavelet fusion extension for ENVI written by David Gorodetzky (11-08-2005) was used:
- Wavelet Fusion is an ENVI extension available from the ITTVIS codebank https://esriaustralia.com.au/envi
- The input images are transformed into wavelet space. Their wavelet coefficients are combined. Then an inverse wavelet transform is applied to the combined wavelet coefficients to create the fused image.
- Fusion strength: the ratios used to blend together the wavelet coefficients of each image at each decomposition level. The settings used were:
- Image A: Multispectral image
- Image B: PAN image
- Map projection: Match Image B (PAN)
- Fusion strength: 50:50
- Additional options: defaults
- Output file name: include psdwt (pansharpened with discrete wavelet transform)

Orthorectification

Orthorectification parameters in ENVI:
- Orthorectification of the pansharpened image was done without GCPs as the match between the DEM and the QuickBird image was very good. Co-registration was applied after orthorectification to fine-tune the image rectification and to match the QuickBird image to the 2004 IKONOS image (metadata ID: "SIC_266_267_georectification".
- RPC model based on the *.rpb file from the panchromatic band -RADARSAT 2002 DEM was first reprojected in ArcGIS, so that it is in a geographical coordinate system.
- The DEM resampling was set to Cubic convolution because it is upsampled to a higher resolution and cubic convolution results in a smoother interpolation.
- The Geoid offset was set to the default of 0.0 as no accurate geoid offset was found on the Geoscience Australia website.
- The projection was set to UTM, Zone 43 South with a WGS-84 Datum.
- The pixel size was set to 0.6 m in both X and Y directions.

This procedure worked however there were areas along the coastline which appeared to have some sort of remnant coast showing in the image (translucent coastal wave appeared on the coastal vegetation, i.e. shadowing effect). Details of this issue (and how it was corrected) are included in the referenced PDF.

Access

A PDF document providing further details is available for download from the provided URL.

Access to the image itself is limited owing to copyright issues. Contact the Australian Antarctic Data Centre for details and further information.

Temporal Coverages

• Start date: 2003-01-17 - Stop date: 2003-01-17

Spatial Coverages

Data Resolution

Science Keywords

• EARTH SCIENCE > SPECTRAL/ENGINEERING > VISIBLE WAVELENGTHS > VISIBLE IMAGERY

Use Constraints

This data set conforms to the CCBY Attribution License (http://creativecommons.org/licenses/by/4.0/).

Please follow instructions listed in the citation reference provided at http://data.aad.gov.au/aadc/metadata/citation.cfm?entry_id=SIC_253_georectification when using these data.