ALOS Geometric and Radiometric Specifications

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The ALOS (Advanced Land Observing Satellite) imagery is subject to regular assessment by the ALOS Calibration/Validation Team (Cal/Val). Members of the team include representatives from the Japan Aerospace Exploration Agency (JAXA) and other approved scientists. The results of the Cal/Val activities are assessed to determine if upgrades can be made to the ALOS product generation software which would lead to improved product accuracy and quality.

We installed JAXA supplied upgrades to our ALOS processing software in May and September 2007, resulting in improved radiometric and geometric specifications for products generated since those dates. The following table contains links to JAXA ALOS specifications relating to the time of product generation by Geoscience Australia.

Date of producing an ALOS product Processing software version Radiometric and geometric specifications (according to JAXA's testing)
December 2006 - May 2007 Ver 3 Initial Calibration Result of JAXA standard products (As of October 23, 2006)
May 2007 - September 2007 Ver 4 Calibration Result of JAXA standard products (As of March 29, 2007)
September 2007 onwards Ver 4.04 Calibration Result of JAXA standard products (As of September 28, 2007)

These specifications have been determined by the JAXA Cal/Val Team based on ground control points (GCPs) located at Cal/Val sites. Note that the JAXA figures have been derived after taking into account the effect of relief displacement (dependant on viewing angle and terrain height). Terrain relief displacement exists in standard ALOS products and this effect is significant in ALOS scenes acquired at large off-nadir viewing angle in areas of undulating terrain.

We assess on a regular basis the positional accuracy of our ALOS products and the result is shown in the table below.

Satellite/Sensor/Level Locational Accuracy
ALOS PRISM Wide Swath: Orthocorrected Image Dependent on accuracy of GCPs and DEM used. Our default orthocorrection uses image chips taken from the Geoscience Australia Landsat 7 Pan mosaic. This will provide products with 15 metre accuracy. We encourage clients that prior to ordering they should consider providing us ground control with better locational accuracy.
ALOS PRISM: Path and Map Image Products 95% of products better than ± 279 m
ALOS AVNIR-2: Path and Map Image Products 95% of products better than ± 481 m
ALOS PALSAR: Path and Map Image Products 95% of products better than ± 372 m

Special enhancement for AVNIR-2 products

We are improving the positional accuracy of AVNIR-2 Map Oriented products by automatically matching the AVNIR-2 data to a Landsat ortho corrected panchromatic reference image for scenes acquired over the Australian mainland. The ER Mapper and ENVI headers which accompany AVNIR-2 Map Oriented CEOS format products will be updated to reflect the improved positioning. This change will not be reflected in the CEOS image data and internal metadata. The GeoTIFF format option contains the improved positioning information because it is utilises the ER Mapper header information.

Topic contact: earth.observation@ga.gov.au Last updated: February 10, 2012