Updated: 26 October 2007

ALOS Geometric and Radiometric Specifications

The Advanced Land Observing Satellite (ALOS) imagery is subject to regular assessment by the ALOS Calibration/Validation Team (Cal/Val). Members of the Team comprise 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 that would lead to improved product accuracy and quality.

ACRES has 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 provides links to the JAXA ALOS specifications, depending on the time of product generation by ACRES.

Date of ACRES 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)

Table 1: ALOS radiometric and geometric specifications, dependent on time of product generation.

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 ACRES standard ALOS products and this effect is significant in ALOS scenes acquired at large off-nadir viewing angle in areas of undulating terrain.

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

Satellite/Sensor/Level	Positional 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

Table 2 ACRES ALOS products positional accuracy

Special ACRES enhancement for AVNIR-2 products

ACRES is improving the positional accuracy of AVNIR-2 Map Oriented products by automatically matching the AVNIR-2 data to ACRES 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 as it is utilises the ER Mapper header information.