Abstract:
The orthorectification of the QuickBird image (15 December 2006, SIC 463) was done as part of the Heard Island AAS2939 project (Lucieer et al.). 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 (http://www.ittvis.com).
Quality
The sequence of processing steps used were as follows:
Pansharpening - Fuse or merge the high-resolution panchromatic band with the lower resolution multispectral bands to create a high-resolution multispectral image based on an image transform. - Panchromatic band has to overlap with multispectral bands in wavelengths. - Wavelet-based pansharpening is more correct ... from a spectral perspective than ENVIs pansharpening algorithms, such as HSV, Brovey, Gram-Schmidt, PCA, and CN. - Wavelet Fusion is an ENVI extension available from the ITTVIS codebank http://www.ittvis.com/UserCommunity/CodeLibrary.aspx - 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: - 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 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.
Co-registration
Image to image GCPs were selected using a geographic link between the images to aid in feature identification.94 GCPs were identified spread out over the image. The RMS value for a 1st order polynomial was 17.31 pixels (10.4 m). However, as we applied a triangulation (rubber sheeting) transformation, this RMS value has no significant meaning. The QuickBird image was warped using the triangulation transformation method with nearest neighbour image resampling. Output: qb_15dec2006_ps_orc_tri2.bsq
Access Constraints
A PDF document providing further details is available for download from the URL given below.
Access to the image itself is limited owing to copyright issues. Contact the Australian Antarctic Data Centre for details and further information.
