The compilation of global Landsat data-sets and the ever-lowering costs of computing now make it feasible to monitor the Earth’s land cover at Landsat resolutions of 30 m.In this article,we describe the methods to cr...The compilation of global Landsat data-sets and the ever-lowering costs of computing now make it feasible to monitor the Earth’s land cover at Landsat resolutions of 30 m.In this article,we describe the methods to create global products of forest cover and cover change at Landsat resolutions.Nevertheless,there are many challenges in ensuring the creation of high-quality products.And we propose various ways in which the challenges can be overcome.Among the challenges are the need for atmospheric correction,incorrect calibration coefficients in some of the data-sets,the different phenologies between compila-tions,the need for terrain correction,the lack of consistent reference data for training and accuracy assessment,and the need for highly automated character-ization and change detection.We propose and evaluate the creation and use of surface reflectance products,improved selection of scenes to reduce phenological differences,terrain illumination correction,automated training selection,and the use of information extraction procedures robust to errors in training data along with several other issues.At several stages we use Moderate Resolution Spectro-radiometer data and products to assist our analysis.A global working prototype product of forest cover and forest cover change is included.展开更多
Wetlands play an important role in the provision of ecosystem services,ranging from the regulation of hydrological systems to carbon sequestration and biodiversity habitat.This paper reports the mapping of Indonesia’...Wetlands play an important role in the provision of ecosystem services,ranging from the regulation of hydrological systems to carbon sequestration and biodiversity habitat.This paper reports the mapping of Indonesia’s wetland cover as a single thematic class,including peatlands,freshwater wetlands,and mangroves.Expert-interpreted training data were used to identify wetland formations including areas of likely past wetland extent that have been converted to other land uses.Topographical indices(Shuttle Radar Topography Mission-derived)and optical(Landsat)and radar(PALSAR)image inputs were used to build a bagged classification tree model based on training data in order to generate a national-scale map of wetland extent at a 60 m spatial resolution.The resulting wetland map covers 21.0%(39.6 Mha)of Indonesia’s land,including 25.2% of Sumatra(11.9 Mha),22.9% of Kalimantan(12.2 Mha),and 28.9% of Papua(11.8 Mha).Results agree with existing image-interpreted products from Indonesia’s Ministries of Forestry and Agriculture and Wetlands International(89% overall agreement),and with the Ministry of Forestry forest inventory data for Sumatra and Kalimantan(91% overall agreement).An internally consistent algorithm-derived national wetland extent map can be used to quantify changing rates of land conversion inside and outside of wetlands.Additionally,wetlands extent can be used to efficiently allocate field resources in national assessments of wetland sub-types such as peatlands,which are a current focus of policies aiming to reduce carbon emissions from land use change.展开更多
基金support from the NASATerrestrial Ecology Program which led to the creation of LEDAPS on which much of this work is based.We acknowledge the help of two people in particular from USGS EROS:Gyanesh Chander helped to identify the GLS 1990 images that have most recent USGS calibration coefficients(?50%of the GLS 1990 data-set).Rachel Headley helped us obtain the GLS data-sets.She also helped significantly with our reordering of the GLS 1990 images that had good calibration coefficients。
文摘The compilation of global Landsat data-sets and the ever-lowering costs of computing now make it feasible to monitor the Earth’s land cover at Landsat resolutions of 30 m.In this article,we describe the methods to create global products of forest cover and cover change at Landsat resolutions.Nevertheless,there are many challenges in ensuring the creation of high-quality products.And we propose various ways in which the challenges can be overcome.Among the challenges are the need for atmospheric correction,incorrect calibration coefficients in some of the data-sets,the different phenologies between compila-tions,the need for terrain correction,the lack of consistent reference data for training and accuracy assessment,and the need for highly automated character-ization and change detection.We propose and evaluate the creation and use of surface reflectance products,improved selection of scenes to reduce phenological differences,terrain illumination correction,automated training selection,and the use of information extraction procedures robust to errors in training data along with several other issues.At several stages we use Moderate Resolution Spectro-radiometer data and products to assist our analysis.A global working prototype product of forest cover and forest cover change is included.
基金provided by AUSAID through the Indonesian National Carbon Accounting System projectby the United States National Aeronautics and Space Administration’s Land Cover and Land Use Change program through grant NNG06GD95G.
文摘Wetlands play an important role in the provision of ecosystem services,ranging from the regulation of hydrological systems to carbon sequestration and biodiversity habitat.This paper reports the mapping of Indonesia’s wetland cover as a single thematic class,including peatlands,freshwater wetlands,and mangroves.Expert-interpreted training data were used to identify wetland formations including areas of likely past wetland extent that have been converted to other land uses.Topographical indices(Shuttle Radar Topography Mission-derived)and optical(Landsat)and radar(PALSAR)image inputs were used to build a bagged classification tree model based on training data in order to generate a national-scale map of wetland extent at a 60 m spatial resolution.The resulting wetland map covers 21.0%(39.6 Mha)of Indonesia’s land,including 25.2% of Sumatra(11.9 Mha),22.9% of Kalimantan(12.2 Mha),and 28.9% of Papua(11.8 Mha).Results agree with existing image-interpreted products from Indonesia’s Ministries of Forestry and Agriculture and Wetlands International(89% overall agreement),and with the Ministry of Forestry forest inventory data for Sumatra and Kalimantan(91% overall agreement).An internally consistent algorithm-derived national wetland extent map can be used to quantify changing rates of land conversion inside and outside of wetlands.Additionally,wetlands extent can be used to efficiently allocate field resources in national assessments of wetland sub-types such as peatlands,which are a current focus of policies aiming to reduce carbon emissions from land use change.
