|2016.5.10:||Dataset description document has been updated (Ver. A). [NEW!]|
|2016.4.6:||(Correction) of a figure 1 used in [Global 25m Resolution PALSAR-2/PALSAR Mosaic and Forest/Non-Forest Map]|
|2016.3.28:||PALSAR-2 global mosaic and forest/non-forest map for Japan in 2015 are released.|
|2016.3.28:||Low resolution forest/non-forest maps (0.25 degrees and 1km) are released.|
|2016.1.25:||PALSAR-2 global mosaic and forest/non-forest map in 2015.
* Data for Japan (using polarimetry mode) will be available soon.
|2014.1.16:||PALSAR global mosaic and forest/non-forest map in 2007, 2008, 2009 and 2010.|
Global 25m resolutions PALSAR-2/PALSAR mosaic and forest/non-forest map are free and open dataset generated by applying JAXA's powerful processing and sophisticated analysis method/techniques to a lot of images obtained with Japanese L-band Synthetic Aperture Radars (PALSAR and PALSAR-2) on Advanced Land Observing Satellite (ALOS) and Advanced Land Observing Satellite-2 (ALOS-2).
For understanding and responding to global environmental changes such as global warming and loss of biodiversity, timely assessment of deforestation and forest degradation is essential. Global monitoring with satellite remote sensing is one of the most effective approaches to detect land surface changes because satellites can provide wall-to-wall images covering wide areas periodically. L-band Synthetic Aperture Radars (SAR) on ALOS and ALOS-2 can observe the land surface even under clouds, and therefore the L-band SAR data have been providing useful information about forest changes in tropical region.
The global 25m resolutions PALSAR/PALSAR-2 mosaic is a seamless global SAR image created by mosaicking the SAR images in backscattering coefficients measured by PALSAR/PALSAR-2, where all the strip data within 10x10 degrees in latitude and longitude are path-processed and mosaicked for the sake of processing efficiency. Correction of geometric distortion specific to SAR (ortho-rectification) and topographic effects on image intensity (slope correction) are applied to make forest classification easy. The size of one pixel is approximately 25 meter by 25 meter. The temporal interval of the mosaic is generally 1 year.
The global forest/non-forest map (FNF) is generated by classifying the backscattering intensity values in the global 25m resolution PALSAR-2/PALSAR mosaic so that strong and low backscatter in HV-polarization are classified "forest" (colored in green) and "non-forest" (colored in yellow), respectively. Here, "forest" is defined as the natural forest with the area larger than 0.5ha and forest cover over 90%, as same to the FAO definition. Since the radar backscatter from the forest depends on the region (climate zone), the classification of Forest/Non-forest is conducted by using the region dependent threshold of backscatter. The classification accuracy is more than 84% according to the comparison with reference data such as in-situ photos and high-resolution optical satellite images. Figure 1 and Figure 2 illustrate global mosaic images and an example of Borneo island.
JAXA plans to update the FNF classification algorithm to improve the accuracy. Please let us know if there are comments or requests for the dataset.
Figure 1: (Left top) PALSAR global mosaic in 2009, (right top) PALSAR forest/non-forest map in 2009, (left bottom) PALSAR-2 global mosaic in 2015, and (right bottom) PALSAR-2 forest/non-forest map in 2015.
Figure 2: Deforestation (red colored areas in the map) in Borneo island during 2010 to 2015.
3. Dataset description
- SAR processing algorithm: Sigma-SAR IMAGE (for strip processing) and Sigma-SAR MOSAIC (for mosaicking)
- Data format: binary image file + header file
- Resolution: approx. 25 m (original product), 100 m/1 km/0.25 deg. (low resolution product, only forest/non-forest map)
- Contents: ortho and slope corrected backscattering coefficient (HH and HV polarization), forest/non-forest map, observation date, local incidence angle, processing mask information
For details, please see the dataset description document (Ver. A, PDFfile, 320KB).
Please register your information from following URL to download the dataset. It is required your e-mail address.
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The dataset download site is
5. Note for data use
- JAXA retains ownership of the dataset. JAXA cannot guarantee any problem caused by or possibly caused by using the datasets.
- Anyone wishing to publish any results using the datasets should clearly acknowledge the ownership of the data in the publication.
- Note that the datasets are provided free of charge, but are available for research and educational purposes only. It is prohibited to use the datasets for commercial, profit-making purposes without JAXA's consent. If users wish to use the datasets for such purposes, please make contact to JAXA.
ALOS-2/ALOS Science Project
Earth Observation Research Center (EORC)
Japan Aerospace Exploration Agency (JAXA)
- Masanobu Shimada, Takuya Itoh, Takeshi Motooka, Manabu Watanabe, Shiraishi Tomohiro, Rajesh Thapa, and Richard Lucas, "New Global Forest/Non-forest Maps from ALOS PALSAR Data (2007-2010)", Remote Sensing of Environment, 155, pp. 13-31, December 2014. DOI=10.1016/j.rse.2014.04.014.
- New global 25m-resolution PALSAR mosaic and forest/non-forest map (2007-2010) - version 1: (Jan. 16, 2014)
- Generation of Global Forest/Non-forest map Using ALOS/PALSAR: (Oct. 21, 2010)
- PALSAR 10m mosaic: (Nov. 4, 2010)