207 research outputs found
Remote Sensing of Snow Cover Using Spaceborne SAR: A Review
The importance of snow cover extent (SCE) has been proven to strongly link with various
natural phenomenon and human activities; consequently, monitoring snow cover is one the most
critical topics in studying and understanding the cryosphere. As snow cover can vary significantly
within short time spans and often extends over vast areas, spaceborne remote sensing constitutes
an efficient observation technique to track it continuously. However, as optical imagery is limited
by cloud cover and polar darkness, synthetic aperture radar (SAR) attracted more attention for its
ability to sense day-and-night under any cloud and weather condition. In addition to widely applied
backscattering-based method, thanks to the advancements of spaceborne SAR sensors and image
processing techniques, many new approaches based on interferometric SAR (InSAR) and polarimetric
SAR (PolSAR) have been developed since the launch of ERS-1 in 1991 to monitor snow cover under
both dry and wet snow conditions. Critical auxiliary data including DEM, land cover information,
and local meteorological data have also been explored to aid the snow cover analysis. This review
presents an overview of existing studies and discusses the advantages, constraints, and trajectories of
the current developments
A review of the contributions of Alexander F.H. Goetz to imaging spectroscopy
All aspects of the science and engineering of imaging spectrometry have been advanced by the work of Dr. Alexander F.H. Goetz over the past 30 years. Dr. Goetz’s pioneering efforts were among the first to realize that it was feasible to obtain laboratory like spectra from space that would quantify earth materials based on biogeochemistry. He has made fundamental contributions to developing high spectral resolution field spectrometers and airborne imaging spectrometers, and to the image processing software and atmospheric correction software needed to analyze the data. These parallel developments in core technologies have made imaging spectroscopy available to a wide range of users of varying user expertise and disciplines, thus enabling the current state of rapid advances in the use of this data
Global Characterization and Monitoring of Forest Cover Using Landsat Data: Opportunities and Challenges
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 compilations, the need for terrain correction, the lack of consistent reference data for training and accuracy assessment, and the need for highly automated characterization 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 Spectroradiometer data and products to assist our analysis. A global working prototype product of forest cover and forest cover change is included
Spacelab Science Results Study
Beginning with OSTA-1 in November 1981 and ending with Neurolab in March 1998, a total of 36 Shuttle missions carried various Spacelab components such as the Spacelab module, pallet, instrument pointing system, or mission peculiar experiment support structure. The experiments carried out during these flights included astrophysics, solar physics, plasma physics, atmospheric science, Earth observations, and a wide range of microgravity experiments in life sciences, biotechnology, materials science, and fluid physics which includes combustion and critical point phenomena. In all, some 764 experiments were conducted by investigators from the U.S., Europe, and Japan. The purpose of this Spacelab Science Results Study is to document the contributions made in each of the major research areas by giving a brief synopsis of the more significant experiments and an extensive list of the publications that were produced. We have also endeavored to show how these results impacted the existing body of knowledge, where they have spawned new fields, and if appropriate, where the knowledge they produced has been applied
Summary of Current Radiometric Calibration Coefficients for Landsat MSS, TM, ETM+, and EO-1 ALI Sensors
This paper provides a summary of the current equations and rescaling factors for converting calibrated Digital Numbers (DNs) to absolute units of at-sensor spectral radiance, Top-Of- Atmosphere (TOA) reflectance, and at-sensor brightness temperature. It tabulates the necessary constants for the Multispectral Scanner (MSS), Thematic Mapper (TM), Enhanced Thematic Mapper Plus (ETM+), and Advanced Land Imager (ALI) sensors. These conversions provide a basis for standardized comparison of data in a single scene or between images acquired on different dates or by different sensors. This paper forms a needed guide for Landsat data users who now have access to the entire Landsat archive at no cost
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