Evaluating the effectiveness of smoothing algorithms in the absence of ground reference measurements

Time series of vegetation indices like NDVI are used in numerous applications ranging from ecology to climatology and agriculture. Often, these time series have to be filtered before application. The smoothing removes noise introduced by undetected clouds and poor atmospheric conditions. Ground reference measurements are usually difficult to obtain due to the medium/coarse resolution of the imagery. Hence, new filter algorithms are typically only (visually) assessed against the existing smoother. The present work aims to propose a range of quality indicators that could be useful to qualify filter performance in the absence of ground-based reference measurements. The indicators comprise (i) plausibility checks, (ii) distance metrics and (iii) geostatistical measures derived from variogram analysis. The quality measures can be readily derived from any imagery. For illustration, a large SPOT VGT dataset (1999–2008) covering South America at 1 km spatial resolution was filtered using the Whittaker smoother.

[1]  Paul F. Velleman,et al.  Definition and Comparison of Robust Nonlinear Data Smoothing Algorithms , 1980 .

[2]  C. Justice,et al.  Analysis of the phenology of global vegetation using meteorological satellite data , 1985 .

[3]  B. Holben Characteristics of maximum-value composite images from temporal AVHRR data , 1986 .

[4]  W. Dulaney,et al.  Normalized difference vegetation index measurements from the Advanced Very High Resolution Radiometer , 1991 .

[5]  A. Belward,et al.  The Best Index Slope Extraction ( BISE): A method for reducing noise in NDVI time-series , 1992 .

[6]  Jesslyn F. Brown,et al.  Measuring phenological variability from satellite imagery , 1994 .

[7]  A. Anyamba,et al.  Interannual variability of NDVI over Africa and its relation to El Niño/Southern Oscillation , 1996 .

[8]  G. Dedieu,et al.  Global-Scale Assessment of Vegetation Phenology Using NOAA/AVHRR Satellite Measurements , 1997 .

[9]  S. Running,et al.  A continental phenology model for monitoring vegetation responses to interannual climatic variability , 1997 .

[10]  K. Wolter,et al.  Measuring the strength of ENSO events: How does 1997/98 rank? , 1998 .

[11]  D. Jupp,et al.  The current and potential operational uses of remote sensing to aid decisions on drought exceptional circumstances in Australia: a review , 1998 .

[12]  D. Fuller,et al.  Trends in NDVI time series and their relation to rangeland and crop production in Senegal, 1987-1993 , 1998 .

[13]  Felix Kogan,et al.  Satellite-Observed Sensitivity of World Land Ecosystems to El Niño/La Niña , 2000 .

[14]  Massimo Menenti,et al.  Mapping vegetation-soil-climate complexes in southern Africa using temporal Fourier analysis of NOAA-AVHRR NDVI data , 2000 .

[15]  W. Verhoef,et al.  Reconstructing cloudfree NDVI composites using Fourier analysis of time series , 2000 .

[16]  M. Kafatos,et al.  Interannual Variability of Vegetation in the United States and Its Relation to El Niño/Southern Oscillation , 2000 .

[17]  Frédéric Baret,et al.  Developments in the 'validation' of satellite sensor products for the study of the land surface , 2000 .

[18]  O. Sala,et al.  Current Distribution of Ecosystem Functional Types in Temperate South America , 2001, Ecosystems.

[19]  J. L. Lovell,et al.  Filtering Pathfinder AVHRR Land NDVI data for Australia , 2001 .

[20]  Jonathan Seaquist,et al.  Improving the estimation of noise from NOAA AVHRR NDVI for Africa using geostatistics , 2001 .

[21]  C. Tucker,et al.  Higher northern latitude normalized difference vegetation index and growing season trends from 1982 to 1999 , 2001, International journal of biometeorology.

[22]  Aaron Moody,et al.  Land-Surface Phenologies from AVHRR Using the Discrete Fourier Transform , 2001 .

[23]  D. Legates,et al.  Crop identification using harmonic analysis of time-series AVHRR NDVI data , 2002 .

[24]  G. Powell,et al.  Terrestrial Ecoregions of the World: A New Map of Life on Earth , 2001 .

[25]  C. Tucker,et al.  Variations in northern vegetation activity inferred from satellite data of vegetation index during 1981 to 1999 , 2001 .

[26]  R. N. Juárez,et al.  ENSO drought onset prediction in northeast Brazil using NDVI , 2001 .

[27]  Per Jönsson,et al.  Seasonality extraction by function fitting to time-series of satellite sensor data , 2002, IEEE Trans. Geosci. Remote. Sens..

[28]  Jiyuan Liu,et al.  Characterization of forest types in Northeastern China, using multi-temporal SPOT-4 VEGETATION sensor data , 2002 .

[29]  Ranga B. Myneni,et al.  Analysis of interannual changes in northern vegetation activity observed in AVHRR data from 1981 to 1994 , 2002, IEEE Trans. Geosci. Remote. Sens..

[30]  Allen H Hurlbert,et al.  The Effect of Energy and Seasonality on Avian Species Richness and Community Composition , 2002, The American Naturalist.

[31]  P. Eilers A perfect smoother. , 2003, Analytical chemistry.

[32]  A. Strahler,et al.  Monitoring vegetation phenology using MODIS , 2003 .

[33]  K. Price,et al.  Response of seasonal vegetation development to climatic variations in eastern central Asia , 2003 .

[34]  J. Kerr,et al.  From space to species: ecological applications for remote sensing , 2003 .

[35]  L. Ji,et al.  Assessing vegetation response to drought in the northern Great Plains using vegetation and drought indices , 2003 .

[36]  A. Skidmore,et al.  Spectral discrimination of vegetation types in a coastal wetland , 2003 .

[37]  Per Jönsson,et al.  TIMESAT - a program for analyzing time-series of satellite sensor data , 2004, Comput. Geosci..

[38]  Jin Chen,et al.  A simple method for reconstructing a high-quality NDVI time-series data set based on the Savitzky-Golay filter , 2004 .

[39]  R. Stöckli,et al.  European plant phenology and climate as seen in a 20-year AVHRR land-surface parameter dataset , 2004 .

[40]  Wolfgang Lucht,et al.  Comparative evaluation of seasonal patterns in long time series of satellite image data and simulations of a global vegetation model , 2004, IEEE Transactions on Geoscience and Remote Sensing.

[41]  T. Sakamoto,et al.  A crop phenology detection method using time-series MODIS data , 2005 .

[42]  A. Belward,et al.  GLC2000: a new approach to global land cover mapping from Earth observation data , 2005 .

[43]  T. D. Mitchell,et al.  An improved method of constructing a database of monthly climate observations and associated high‐resolution grids , 2005 .

[44]  N. Pettorelli,et al.  Using the satellite-derived NDVI to assess ecological responses to environmental change. , 2005, Trends in ecology & evolution.

[45]  R. Myneni,et al.  Potential monitoring of crop production using a satellite-based Climate-Variability Impact Index , 2005 .

[46]  Rasmus Fensholt,et al.  Evaluating MODIS, MERIS, and VEGETATION vegetation indices using in situ measurements in a semiarid environment , 2006, IEEE Transactions on Geoscience and Remote Sensing.

[47]  F. Veroustraete,et al.  Reconstructing pathfinder AVHRR land NDVI time-series data for the Northwest of China , 2006 .

[48]  P. Beck,et al.  Improved monitoring of vegetation dynamics at very high latitudes: A new method using MODIS NDVI , 2006 .

[49]  John F. Mustard,et al.  A curve fitting procedure to derive inter-annual phenologies from time series of noisy satellite NDVI data , 2007 .

[50]  John F. Hermance,et al.  Stabilizing high‐order, non‐classical harmonic analysis of NDVI data for average annual models by damping model roughness , 2007 .

[51]  A. K. Skidmore,et al.  A ground‐validated NDVI dataset for monitoring vegetation dynamics and mapping phenology in Fennoscandia and the Kola peninsula , 2007 .

[52]  P. Atkinson,et al.  Exploring the geostatistical method for estimating the signal-to-noise ratio of images , 2007 .

[53]  John F. Mustard,et al.  Extracting Phenological Signals From Multiyear AVHRR NDVI Time Series: Framework for Applying High-Order Annual Splines With Roughness Damping , 2007, IEEE Transactions on Geoscience and Remote Sensing.

[54]  Giles M. Foody,et al.  Image-based method for noise estimation in remotely sensed data , 2007, SPIE Remote Sensing.

[55]  Fabienne Maignan,et al.  Interannual vegetation phenology estimates from global AVHRR measurements: Comparison with in situ data and applications , 2008 .

[56]  Erwin Ulrich,et al.  Evaluation of the onset of green-up in temperate deciduous broadleaf forests derived from Moderate Resolution Imaging Spectroradiometer (MODIS) data , 2008 .

[57]  Y. Knyazikhin,et al.  Validation and intercomparison of global Leaf Area Index products derived from remote sensing data , 2008 .

[58]  Clement Atzberger,et al.  Estimation of inter-annual winter crop area variation and spatial distribution with low resolution NDVI data by using neural networks trained on high resolution images , 2009, Remote Sensing.

[59]  Nicholas C. Coops,et al.  Bird diversity: a predictable function of satellite‐derived estimates of seasonal variation in canopy light absorbance across the United States , 2009 .

[60]  Björn Waske,et al.  Hypertemporal Classification of Large Areas Using Decision Fusion , 2009, IEEE Geoscience and Remote Sensing Letters.

[61]  Jennifer N. Hird,et al.  Noise reduction of NDVI time series: An empirical comparison of selected techniques , 2009 .

[62]  M. Gilabert,et al.  Vegetation dynamics from NDVI time series analysis using the wavelet transform , 2009 .

[63]  Paul H. C. Eilers,et al.  Optimal expectile smoothing , 2009, Comput. Stat. Data Anal..

[64]  Roland Geerken,et al.  An algorithm to classify and monitor seasonal variations in vegetation phenologies and their inter-annual change , 2009 .

[65]  Nicholas C. Coops,et al.  Demonstration of a satellite-based index to monitor habitat at continental-scales , 2009 .