Ground Filtering Algorithms for Airborne LiDAR Data: A Review of Critical Issues

This paper reviews LiDAR ground filtering algorithms used in the process of creating Digital Elevation Models. We discuss critical issues for the development and application of LiDAR ground filtering algorithms, including filtering procedures for different feature types, and criteria for study site selection, accuracy assessment, and algorithm classification. This review highlights three feature types for which current ground filtering algorithms are suboptimal, and which can be improved upon in future studies: surfaces with rough terrain or discontinuous slope, dense forest areas that laser beams cannot penetrate, and regions with low vegetation that is often ignored by ground filters

Assessing the Impact of Extreme Climatic Events on ASpen Defoliation Using MODIS Imagery

Recent studies document the decline of quaking aspen across large geographic areas of North America.Extreme climatic events are possible contributors to the decline, and drought is often cited as an important driver of aspen phenology. Little is known, however, about the effects of spring freeze events on aspenphenology, even though such events are projected to occur more frequently in future. This study usesmoderate resolution imaging spectrometer (MODIS) imagery to assess the spatial pattern and magnitude of damage to aspen forests during spring freeze and summer drought events that occurred in Utah in 2007. The analysis finds above normal Normalized Difference Vegetation Index (NDVI) in early spring, and below normal NDVI following the freeze event and during the summer drought. Aspen damage is concentrated in certain terrain classes, depending on the type of extreme climatic event. These findings suggest there are predictable patterns of aspen defoliation that identify aspen stands vulnerable to extreme climatic events

Net primary production and gross domestic product in China derived from satellite imagery

Since the 1980s Chinese economic reform has greatly accelerated its economic growth while in contrast China's environment is increasingly degraded. The Chinese government has recognized that environmental protection and sustainable economic development can promote mutual and sustainable co-development of the economy and the environment as a basic national principle. This paper examines the interactions between economic development and environmental change in China that were compared and analyzed for the years 1996 and 2000. Net primary production (NPP) was selected as a proxy evaluator of ecosystems and gross domestic product (GDP) was chosen as a proxy evaluator of economic development. An NPP change map was produced with Advanced Very High Resolution Radiometer (AVHRR) summed annual NPP imagery products. The Defense Meteorological Satellite Program's Operational Linescan System (DMSP/OLS) nighttime imagery was used to produce a Chinese GDP change map. An integrated map was produced to exhibit the combined changes of NPP and GDP. This map showed that in the regions with increased GDP, NPP decreased but the regions with no GDP change were smaller in area for NPP increase while larger in area for NPP decrease. The changing pattern of NPP varied with the developing level of GDP at province level. A province's development of GDP is controlled by its accessibility to natural resources. Interactions between NPP and GDP are greatly affected by factors of spatial location aside from human factors and natural systems' characteristics.Net primary production (NPP) Gross domestic product (GDP) Nighttime image Integrative analysis