Takuya Itoh

Contribution of L-Band SAR to Systematic Global Mangrove Monitoring

Information on the status of and changes in mangroves is required for national and international policy development, implementation and evaluation. To support these requirements, a component of the Japan Aerospace Exploration Agencys (JAXA) Kyoto and Carbon (KC (2) to quantify changes in the structure and associated losses and gains of carbon on the basis of canopy height and above- ground biomass (AGB) estimated from the shuttle radar topographic mission (SRTM; acquired 2000), the ice, cloud and land-elevation satellite (ICESAT) geoscience laser altimeter system (GLAS; 2003-2010) and L-band backscatter data; (3) to determine likely losses and gains of tree species diversity through reference to International Union for the ConservationofNature(IUCN)globalthematiclayersonthedistributionofmangrovespecies;and(4)tovalidatemapsof changesintheextentofmangroves,primarilythroughcomparisonwithdensetime-seriesofLandsatsensordataandtouse these same data to describe the causes and consequences of change. The paper outlines and justifies the techniques being implementedandtherolethattheGMWmightplayinsupportingnationalandinternationalpoliciesthatrelatespecifically to the long-term conservation of mangrove ecosystems and the services they provide to society.

Generation of 10m resolution PALSAR and JERS-SAR mosaic and forest/non-forest maps for forest carbon tracking

The Japan Aerospace Exploration Agency (JAXA) has produced the worlds first 10m resolution L-band SAR global mosaic datasets. These data sets were generated to monitor forest changes from the 1990s to present. SRTM-3 (90m resolution) DEM was used to correct the terrain-induced SAR intensity variations and the ortho-rectification. Both corrections were applied for geometric and radiometric calibration purposes. The data sets are useful to monitor the temporal forest cover and forest change, and were used to derive forest/non-forest information.

An approach to monitoring mangrove extents through time-series comparison of JERS-1 SAR and ALOS PALSAR data

Between 2007 and 2010, Japan’s Advanced Land Observing Satellite (ALOS) Phased Arrayed L-band Synthetic Aperture Radar (PALSAR) captured dual polarization HH and HV data across the tropics and sub-tropics. A pan tropical dataset of Japanese Earth Resources Satellite (JERS-1) SAR (HH) data was also acquired between 1995 and 1998. The provision of these comparable cloud-free datasets provided an opportunity for observing changes in the extent of coastal mangroves over more than a decade. Focusing on nine sites distributed through the tropics, this paper demonstrates how these data can be used to backdate and update existing baseline maps of mangrove extent. The benefits of integrating dense time-series of Landsat sensor data for both validating assessments of change and determining the causes of change are outlined. The approach is evaluated for wider application across the geographical range of mangroves in order to advance the development of JAXA’s Global Mangrove Watch (GMW) program.

Generation of the first PALSAR-2 global mosaic 2014/2015 and change detection between 2007 and 2015 using the PALSAR and PALSAR-2

Decreasing the carbon emission from the deforestation and forest degradation is one of the issues that the humans need to tag for sustaining the Earth. Monitoring the forest from the space is the recent achievements that the space agencies contribute. Measuring the forest cover change is being conducted by using the high resolution optical and/or SAR images. ALOS-2 has been on-orbit carrying the L-band SAR since May 24, 2014. After more than one year data acquisition and related processing, the first version of the 25-m resolution global PALSAR-2 mosaic dataset from the 2014-2015 acquisitions, forest-non-forest map, and the forest cover change from 2007 to 2015 were generated.

The Global Mangrove Watch—A New 2010 Global Baseline of Mangrove Extent

This study presents a new global baseline of mangrove extent for 2010 and has been released as the first output of the Global Mangrove Watch (GMW) initiative. This is the first study to apply a globally consistent and automated method for mapping mangroves, identifying a global extent of 137,600 km2. The overall accuracy for mangrove extent was 94.0% with a 99% likelihood that the true value is between 93.6–94.5%, using 53,878 accuracy points across 20 sites distributed globally. Using the geographic regions of the Ramsar Convention on Wetlands, Asia has the highest proportion of mangroves with 38.7% of the global total, while Latin America and the Caribbean have 20.3%, Africa has 20.0%, Oceania has 11.9%, North America has 8.4% and the European Overseas Territories have 0.7%. The methodology developed is primarily based on the classification of ALOS PALSAR and Landsat sensor data, where a habitat mask was first generated, within which the classification of mangrove was undertaken using the Extremely Randomized Trees classifier. This new globally consistent baseline will also form the basis of a mangrove monitoring system using JAXA JERS-1 SAR, ALOS PALSAR and ALOS-2 PALSAR-2 radar data to assess mangrove change from 1996 to the present. However, when using the product, users should note that a minimum mapping unit of 1 ha is recommended and that the error increases in regions of disturbance and where narrow strips or smaller fragmented areas of mangroves are present. Artefacts due to cloud cover and the Landsat-7 SLC-off error are also present in some areas, particularly regions of West Africa due to the lack of Landsat-5 data and persistence cloud cover. In the future, consideration will be given to the production of a new global baseline based on 10 m Sentinel-2 composites.

Regenerated ALOS-2/PALSAR-2 global mosaics 2016 and 2014/2015 for forest observations

ALOS-2/PALSAR-2 25-m spaced global mosaic has been produced as the L-band SAR forest monitoring dataset selected from the best acquisitions over the global land and year 2014 and 2015, as the resume of the dataset after pausing the ALOS/PALSAR on 2011 April 22, in the end of 2015. Detailed evaluation results showed some image degradations compared to ALOS/PALSAR: visible stripes across the neighboring strips. The possible causes are 1) less overlapping area between two neighboring strips and needs careful area selection for the radiometric balancing, and 2) antenna elevation pattern needed some more calibration. These two points were well recovered as the recalibration processing in 2016. We are creating the new version of the mosaic as of now. In this paper, we will describe the details of recalibrated and regenerated PALSAR-2 mosaic products for 2014/2015 and 2016 using the improved radiometric calibration algorithm.