AFIDS, a Precision Automatic Co-Registration Process for Spacecraft Sensors
Abstract
AFIDS is the acronym for the Automated Fusion of Image Data System developed recently at JPL under funding from ESTO and other sources, and currently being distributed to interested users in the US government. Automated sub-pixel co-registration and ortho-rectification of satellite imagery is required for precise change detection and analysis of low- (e.g. 1-4km weather satellite), moderate- (e.g. 30m Landsat) and high- resolution (e.g. Ikonos and Quickbird) space sensors. The procedure is "automated" in the sense that human-initiated tiepoint selection is not required, but ephemeris information associated with an image is relied upon to initiate the co-registration process. The methodology employs the additive composition of all pertinent dependent and independent parameters contributing to image-to-image tiepoint misregistration within a satellite scene. Mapping and orthorectification (correction for elevation effects) of satellite imagery defies exact projective solutions because the data are not obtained from a single point (like a camera), but as a continuous process from the orbital path. Standard image processing techniques can apply approximate solutions with sufficient accuracy, but some advances in the state-of-the-art had to be made for precision change-detection and time-series applications where relief offsets become a controlling factor. The basic technique first involves correlation and warping of raw satellite data points to an orthorectified Landsat (30m) or Controlled Image Base (1 or 5m) database to give an approximate mapping. Then digital elevation models are used to correct perspective shifts due to height and view-angle. This image processing approach requires from two (e.g. geosynchronous weather satellite imagery) to four (e.g. polar weather satellite imagery) sequential processing steps that warp the dataset by resampling pixel values. To avoid degradation of the data by multiple resampling, each warp is represented by an ultra-fine grid of tiepoints. For successive warps, the grids are composed mathematically into a single grid such that only one re-sampling occurs. Ultra-fine grids can currently be up to 1000 x 1000, or one million points. Several examples of precision change detection have been undertaken using Hyperion, Advanced Land Imager (ALI), ASTER, NOAA/GOES/VISR, NOAA/POES/AVHRR, MODIS Terra and Aqua, Ikonos, and Quickbird.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2004
- Bibcode:
- 2004AGUFMSF51A..05B
- Keywords:
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- 9820 Techniques applicable in three or more fields;
- 1694 Instruments and techniques;
- 1640 Remote sensing