1. Enhancing Resilience in a Changing Climate/ Renforcer la résilience en face de changements climatiques Earth Sciences Sector /Secteur des Sciences de la Terre dry year New CCRS AVHRR Processing System (CAPS) to Meet GCOS/CEOS Geometric Accuracy Requirements Konstantin V. Khlopenkov, Alexander P. Trishchenko Accurate image georeferencing including orthorectification is essential for analysis of SCDR (Satellite Climate Data Records) for annual variability, trends, indicators. Precise geolocation is fundamental for climate applications: Generation of land-water masks Analysis of fire disturbance Landcover maps Long-term data records for NDVI, etc. Incorrect geolocation increases spatial noise in the long-term data records, which masks the real signal or produces biased results. Improved Image Georeferencing Displacement vectors (map projection method) Master image from MODIS. Distribution of selected GCPs. Canadian/CCRS AVHRR Processing System (CAPS) Image displacement is analyzed in the swath projection; Single pass of ortho-rectification (elevation correction); Displacement matrix is solved to adjust the orbit, sensor orientation, and siderial time, in order to correct for geolocation errors; Uses MODIS composite imagery as a reference (master) image; Uses DEM map 250 m/pix resolution; GCP fitting (chip matching) is applied to laplacians of the images; Achieves sub-pixel geolocation accuracy (1/3 FOV as per GCOS/CEOS requirement); Geolocation files (similar to MOD03) can be produced for each swath. Improved performance. DEM map at 250 m/pixel resolution Ortho-rectification Image Displacement Analysis AVHRR NOAA-18, Aug, 20, 2006 NSS.HRPT.NN.D06232.S1928.E1940.WI 217 GCPs selected GCP Displacement Analysis and Cloud Interference Original images Reference mapSwath imagery Image Laplacians Reference mapSwath imagery Covariance Matrix GCP matching between image Laplacians yields sharper maximum. And also, it is much more efficient in the case of thin/small clouds. Achieving Sub-Pixel Accuracy First step: Fit parabola through 3 points in X and 3 points in Y. The decide, which case is applicable: 6 unknowns from 9 samples 9 unknowns from 12 samples 10 unknowns from 16 samples Image displacement, 1st pass Image displacement after orbit correction    t  s Scan range:  Correction for GHA: 0.982 s AVHRR georeferencing with CAPS Geolocation error is calculated by comparing the reprojected AVHRR scene with MODIS reference (composite) image in LCC projection. AVHRR georeferencing with CAPS (complex winter scene) Summary Some of the advantages and unique features of the CAPS system are: It relies on the high geolocation accuracy of the MODIS 250m/pix imagery. The accuracy in image georeferencing is within ±1/3 pixel along and across the scan direction. Precise orthorectification of the imagery (using the DEM map at 250 m/pix with bilinear interpolation); Sub-pixel accuracy in finding the positioning difference between the images; Efficient reprojection routine that uses the concurrent gradient search and bilinear interpolation; High performance (processing time is ~60–90 sec per granule). The CAPS system is now employed for re-processing the entire AVHRR 1-km archive assembled at CCRS starting from AVHRR NOAA-6. Acknowledgements This work is conducted in the NRCan/ESS Program “ Enhancing Resilience in a Changing Climate” and CCRS/UCS Program Work is also supported by the Canadian Space Agency under the Government Related Initiative Program (GRIP) and Canadian IPY.