Search results for "DIFFERENCE VEGETATION INDEX"
showing 10 items of 141 documents
Remote sensing and climate data as a key for understanding fasciolosis transmission in the Andes: review and update of an ongoing interdisciplinary p…
2006
Fasciolosis caused by Fasciola hepatica in various South American countries located on the slopes of the Andes has been recognized as an important public health problem. However, the importance of this zoonotic hepatic parasite was neglected until the last decade. Countries such as Peru and Bolivia are considered to be hyperendemic areas for human and animal fasciolosis, and other countries such as Chile, Ecuador, Colombia and Venezuela are also affected. At the beginning of the 1990s a multidisciplinary project was launched with the aim to shed light on the problems related to this parasitic disease in the Northern Bolivian Altiplano. A few years later, a geographic information system (GIS…
Impact of climate change and man-made irrigation systems on the transmission risk, long-term trend and seasonality of human and animal fascioliasis i…
2014
Large areas of the province of Punjab, Pakistan are endemic for fascioliasis, resulting in high economic losses due to livestock infection but also affecting humans directly. The prevalence in livestock varies pronouncedly in space and time (1-70%). Climatic factors influencing fascioliasis presence and potential spread were analysed based on data from five mete- orological stations during 1990-2010. Variables such as wet days (Mt), water-budget-based system (Wb-bs) indices and the normalized difference vegetation index (NDVI), were obtained and correlated with geographical distribution, seasonality patterns and the two-decade evolution of fascioliasis in livestock throughout the province. …
Using the ARP-03 for high-resolution mapping of calcic horizons
2013
A b s t r a c t. The aim of this work is to present a fast and cheap method for high-resolution mapping of calcic horizons in vineyards based on geoelectrical proximal sensing. The study area, 45 ha located in southern Sicily (Italy), was characterized by an old, partially dismantled marine terrace and soils with a calcic horizon at different depths. The geoelectrical investigation consisted of a survey of the soil electrical resistivity recorded with the Automatic Resistivity Profiling-03 sensor. The electrical resistivity values at three pseudo-depths, 0-50, 0-100 and 0-170 cm, were spatialized by means of ordinary kriging. A principal component analysis of the three electrical resistivit…
Relative risk estimation of dengue disease at small spatial scale
2017
Abstract Background Dengue is a high incidence arboviral disease in tropical countries around the world. Colombia is an endemic country due to the favourable environmental conditions for vector survival and spread. Dengue surveillance in Colombia is based in passive notification of cases, supporting monitoring, prediction, risk factor identification and intervention measures. Even though the surveillance network works adequately, disease mapping techniques currently developed and employed for many health problems are not widely applied. We select the Colombian city of Bucaramanga to apply Bayesian areal disease mapping models, testing the challenges and difficulties of the approach. Methods…
Insensitivity of Tree-Ring Growth to Temperature and Precipitation Sharpens the Puzzle of Enhanced Pre-Eruption NDVI on Mt. Etna (Italy)
2017
On Mt. Etna (Italy), an enhanced Normalized Difference in Vegetation Index (NDVI) signature was detected in the summers of 2001 and 2002 along a distinct line where, in November 2002, a flank eruption subsequently occurred. These observations suggest that pre-eruptive volcanic activity may have enhanced photosynthesis along the future eruptive fissure. If a direct relation between NDVI and future volcanic eruptions could be established, it would provide a straightforward and low-cost method for early detection of upcoming eruptions. However, it is unclear if, or to what extent, the observed enhancement of NDVI can be attributed to volcanic activity prior to the subsequent eruption. We conse…
Soil Moisture Retrieved From a Combined Optical and Passive Microwave Approach
2016
Abstract With the current remote sensing technology developments, and in particular those at L-band (1.2–1.4 GHz) frequencies such as the Soil Moisture and Ocean Salinity and the Soil Moisture Active and Passive missions, new approaches concerning passive microwave and its combination with existing optical technologies have become of special interest for the estimation of surface soil moisture. One of these new approaches is the combination of optical and passive microwave data based on a semiempirical approach derived from the general radiative transfer equation. The objective of this chapter is to present some applications of the combined optical-passive microwave approaches over several …
CloudSim: A fair benchmark for comparison of methods for times series reconstruction from cloud and atmospheric contamination
2015
Cloud contamination of optical data is a constant and annoying feature of time series analyses, whether while using vegetation indices or surface temperatures, since it tends to decrease artificially the values taken by these parameters. Therefore, any time series analysis of optical data needs a previous step for gap-filling reconstruction of the time series. Numerous techniques have been presented in the literature to carry out this preliminary and mandatory step. However, the evaluation and comparison of these techniques is difficult, since no “truth” time series is available. We present here a probabilistic model (CloudSim) to provide global typical annual time series for NDVI (Normaliz…
Introducing the Time Series Change Visualization and Interpretation (TSCVI) method for the interpretation of global NDVI changes
2021
Abstract This paper presents a novel method for the visualization of changes in vegetation related variables. This method, termed Time Series Change Visualization and Interpretation (TSCVI), allows to summarize changes associated to both vegetation productivity and phenology in a single map. To that end, three metrics are retrieved on an annual basis from plotting NDVI (Normalized Difference Vegetation Index) values on a polar plot. Changes in these metrics are then analyzed and mapped in an IHS (Intensity Hue Saturation) image, where colors indicate changes regarding the growing-season (earlier or later occurrence, stronger or weaker seasonality), while changes associated to productivity a…
Optimizing and comparing gap-filling techniques using simulated NDVI time series from remotely sensed global data
2019
Abstract NDVI (Normalized Difference Vegetation Index) time series usually suffer from remaining cloud presence, even after data pre-processing. To address this issue, numerous gap-filling (or reconstruction) techniques have been developed in the literature, although their comparison has mainly been local to regional, with only two global studies to date, and has led to sometimes contradictory results. This study builds on these different comparisons, by testing different parameterizations for five NDVI temporal profile reconstruction techniques, namely HANTS (Harmonic Analysis of Time Series), IDR (iterative Interpolation for Data Reconstruction), Savitzky-Golay, Asymmetric Gaussian and Do…
Multitemporal analysis of PAL images for the study of land cover dynamics in South America
2006
Pathfinder AVHHR Land (PAL) database has been used for the retrieval of Land Surface Temperature (LST) over South America, which, along with NDVI parameter, will allow the studying of the evolution of the vegetation between July 1981 and September 2001. To this end, a classification has been built, based on PAL NDVI and Reanalysis air temperature at 2 m height data. This classification takes into account both vegetation and thermal patterns, and has been validated by a comparison with CAZALAC's map of arid zones (Centro del Agua para Zonas Aridas y semiaridas de Latino-America y el Caribe), as well as with Global Land Cover Characteristics' classification built by the USGS (United States Ge…