Description
The creation of radiometric terrain corrected (RTC) products was a project of the Alaska Satellite Facility to make SAR data accessible to a broader community of users. RTC removes the geometric and radiometric distortions inherent in synthetic aperture radar (SAR) and the corrected PALSAR data are provided in a GIS-compatible GeoTIFF format. The release of ALOS PALSAR RTC products commenced in October 2014 and was completed a year later. Data used in the RTC project were Fine Beam (FBS, FBD) and Polarimetric (PLR) scenes over all global land areas except Antarctica, Greenland, Iceland, and northern Eurasia.
Included in the package:
- Incidence Angle GeoTIFF, indicating the angle in radians for each pixel
- Layover/Shadow GeoTIFF, indicating where processing was impacted by layover or shadow
- Browse image in GeoJPEG format 1000 x 1000 pixels
- KMZ file with 30-m overlay
- Metadata in ISO 19115 format (xml file)
- Modified SRTM or NED DEM used for RTC processing in GeoTIFF format
Product Summary
Citation
Citation is critically important for dataset documentation and discovery. This dataset is openly shared, without restriction, in accordance with the EOSDIS Data Use Policy.
Copy Citation
Data Center Citation
ALOS PALSAR RTC Product License Agreement
The Alaska Satellite Facility (ASF) grants the End User use of Radiometrically Terrain Corrected (RTC) Advanced Land Observing Satellite (ALOS) PALSAR data if the End User accepts and agrees to the following ALOS PALSAR RTC End User License Agreement. The End User will be deemed to have accepted and agreed to the terms and conditions if the End User starts using ALOS PALSAR RTC data including but not limited to downloading, installing, manipulation or other action.
Section 1 Definitions
1. “End User” means the person, legal business entity, public entity or any other legal entity who obtains the Product and is considered to have accepted this End User License Agreement. In the case of a public entity, the End User is deemed to be only the part, division, etc. of the public entity located at the address to which the Product is supplied, unless otherwise agreed upon by ASF in writing and in advance.
Value Added Product (VAP) – A modified Standard or Derivative Work Product with high-level processing that cannot be converted back to the original product. The high-level processing includes data analysis or combining multiple-satellite data, image processing based on external information, and physical quantity conversion.
2. “Product” means any ALOS RTC satellite data product supplied by ASF. Product is classified as Value Added Product (VAP). Definition of the product types is shown below.
3. “JAXA” means the Japan Aerospace Exploration Agency.
4. “METI” means the Japanese Ministry of Economy, Trade, and Industry.
5. “Related Parties” means the parties that have been involved in the creation, production, distribution or delivery of the Product.
Section 2 Permitted Uses
These data are provided in accordance with NASA’s free and open data policy. There are no restrictions on their use.
Section 3 Prohibited Uses
1. The End User shall not delete, obscure, remove or alter any copyright notice that is contained in or appears on the Product.
Section 4 Intellectual Property Right and Copyright Notice
1. The End user confirms that NASA retains the copyright to the ALOS PALSAR RTC products and that JAXA/METI retains the copyright to the original data from which the Product was derived.
2. The End User owns all intellectual property rights, including copyrights, which result from the End User’s act of interpretation, adaptation, authorship or any other work on the Product resulting in the creation of another VAP. All VAP products must be accompanied by the appropriate copyright notice.
3. The End User agrees that any embodiment of the Product permitted under this agreement shall contain the following copyright notice. The copyright notice shall be prominently displayed and the [Year] field correctly filled with a numerical value corresponding to the year of raw data acquisition.
Copyright Notice for ALOS PALSAR RTC: © NASA [Year], Includes Material © JAXA, METI [Year]
Section 5 Limited Warranty – Disclaimer
1. Neither ASF nor the Related Parties, if any, warrants that the Product is free of bugs, errors, defects or omissions.
2. The Product is provided as is with no warranty of merchantability or fitness for a particular purpose.
3. ASF and the Related Parties shall have no liability to the End User for any damage suffered by the End User or any third party, as a result of using ALOS PALSAR RTC products. This damage is including but not limited to consequential loss and lost earnings.
Section 6 Modification of this Agreement
ASF reserves the right to modify this agreement if necessary and the modified agreement will govern. In the case of modification ASF will announce on ASF internet site.
Section 7 Governing Law and Jurisdiction
This End User License Agreement shall be governed by the laws of the United States of America.
Citing ALOS PALSAR RTC Data and Images
Description | Format | Example |
---|---|---|
PALSAR RTC Data | Dataset: ASF DAAC [year created], [dataset name]; Includes Material ©JAXA/METI [year of data acquisition] | ASF DAAC 2015, ALOS PALSAR_Radiometric_Terrain_Corrected_low_res; Includes Material ©JAXA/METI 2007. |
PALSAR RTC Images | ©JAXA/METI [year of data acquisition] | ©JAXA/METI 2007 |
Strengths and Limitations
NOTES
- Technical information is available in the RTC Product Guide and Algorithm Theoretical Basis Document (ATBD)
- Color browse images are available for dual and quad polarizations (FBD and PLR products)
- More information on the DEMs used for RTC processing can be found below this page in the Known Issues section below
Known Issues
PALSAR RTC DEM Information and Disclaimer
The Digital Elevation Model (DEM) file in the ALOS PALSAR Terrain Corrected product package is not generated from the PALSAR data. It is a copy of an existing DEM modified and used for the radiometric terrain correction process. The pixel spacing of the source DEM was adjusted to match that of the Terrain Corrected image it is packaged with and does not indicate the DEM’s resolution.
The source DEMs used for the ALOS PALSAR Terrain Corrected products are from either the Shuttle Radar Topography Mission (SRTM) or the National Elevation Dataset (NED). Refer to the table and map in the section About the source DEMs used for ALOS PALSAR RTC processing to determine the native resolution and spatial coverage of the source DEMs used for the project.
The source-DEM tiles needed to cover the spatial extents of an uncorrected PALSAR scene were downloaded and mosaicked into a single DEM raster. This mosaicked DEM was processed to apply a geoid correction and then resampled to match the output pixel spacing of the PALSAR scene.
The DEM files packaged with the RTC products are only intended to be used as a reference for evaluating the radiometric terrain correction process. They should not be used in place of a regular DEM, as the geoid correction in preparation for RTC processing alters the elevation values.
Most DEMs are geoid-based and require a conversion before they can be used for terrain correction. The DEM included with an ASF RTC product was converted from the orthometric height of the source DEM to ellipsoid height using the ASF MapReady geoid_adjust tool. This tool applies a geoid correction so that the resulting DEM relates to the ellipsoid.
The GeoidEval Utility is a free online tool that computes the height of the geoid above the WGS84 ellipsoid at a specific location and will show the correction applied to the source DEM used in creating an RTC product.