Learn More
Articles R emote sensing has facilitated extraordinary advances in the modeling, mapping, and understanding of ecosystems. Typical applications of remote sensing involve either images from passive optical systems, such as aerial photography and Landsat Thematic Mapper (Goward and Williams 1997), or to a lesser degree, active radar sensors such as RADARSAT(More)
As the counterfactual model of causality has increased in popularity, sociologists have returned to matching as a research methodology. In this article, advances over the past two decades in matching estimators are explained, and the practical limitations of matching techniques are emphasized. The authors introduce matching methods by focusing first on(More)
Estimation of the amount of carbon stored in forests is a key challenge for understanding the global carbon cycle, one which remote sensing is expected to help address. However, direct estimation of carbon storage in moderate to high biomass forests is difficult for conventional optical and radar sensors. Lidar (light detection and ranging) instruments(More)
[1] Exchange of carbon between forests and the atmosphere is a vital component of the global carbon cycle. Satellite laser altimetry has a unique capability for estimating forest canopy height, which has a direct and increasingly well understood relationship to aboveground carbon storage. While the Geoscience Laser Altimeter System (GLAS) onboard the Ice,(More)
MEASURING HETEROGENEITY IN PREGNANCY FRAMES Calculating neighborhood heterogeneity in pregnancy frames is complicated by the ordinal nature of the pregnancy frame measure, which makes the usual measure of variation for interval measures, the variance, inappropriate. I use an ordinal variation measure developed by Blair and Lacy (2000) that measures(More)
Planned to launch in 2015, ICEsat-2 will measure changes in polar ice coverage and estimate changes in the Earth's bio-mass by measuring vegetation canopy height. ABSTRACT | Satellite and aircraft observations have revealed that remarkable changes in the Earth's polar ice cover have occurred in the last decade. The impacts of these changes, which include(More)
Least squares regression estimates of causal effects are conditional variance weighted estimates of individual-level causal effects. In this paper, we extract from the literature on counterfac-tual causality a simple nine-step routine to determine whether or not the implicit weighting of regression has generated a misleading estimate of the average causal(More)
Continental-scale topographic profiles between 28.45° N and S latitudes acquired by the first flight of the Shuttle Laser Altimeter (SLA) experiment are used to evaluate the vertical accuracy of GTOPO30, a global digital elevation model with a grid spacing of approximately 1 km. GTOPO30 is a compilation of eight sources of elevation information, including(More)
The seasonality of sunlight and rainfall regulates net primary production in tropical forests. Previous studies have suggested that light is more limiting than water for tropical forest productivity, consistent with greening of Amazon forests during the dry season in satellite data. We evaluated four potential mechanisms for the seasonal green-up(More)