ID: 56857
Title: Subpixel snow mapping of the Qinghai- Tibet plateau using MODIS data
Author: Ji Zhu, Jiancheng Shi,Yuanhui Wang
Editor: Freek van der Meer
Year: 2012
Publisher: Elsevier, Vol 18, August 2012
Source: Centre for Ecological Sciences
Reference: None
Subject: International Journal of Applied Earth Observation and Geoinformation
Keywords: Snow cover, Multiple-endmember spectral mixture, analysis, cloud removal
Abstract: In this work, an algorithm for automatic subpixel snow mapping was developed for Moderate Resolution Imaging Spectroradiometer (MODIS) data of the Qinghai-Tibet Plateau. The algorithm consists of two parts: cloud removal and snow mapping. An approach to remove cloud was presented and it was demonstrated to remove thick and thin clouds well from MODIS images. Multiple-endmember spectral mixture analysis was used in the subpixel snow mappign of the Qinghai - Tibet Plateau, and multiple indices (includign the normalized difference vegetation index and normalized difference snow index) were introduced to automatically select the endmembers. Additionally, the combined use of typical and neighboring endmembers was introduced into the unmixing of mixed pixels. Finally, highly accurate snow-cover data of the Qinghai-Tibet Plateau obtained with this algorithm were stored in a spatio-temporal database. The results of the subpixel snow mapping were validated with Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data recorded at the same time as corresponding MODIS data. According to the validation results, the correlation coefficients of the MODIS results versus the ASTER data exceed 0.9, and the root-mean-square errors are less than 0.2.
Location: 231
Literature cited 1: None
Literature cited 2: None
ID: 56856
Title: Estimation of virtual water contained in international trade products using nighttime imagery
Author: Naizhuo Zhao, Eric L Samson
Editor: Freek van der Meer
Year: 2012
Publisher: Elsevier, Vol 18, August 2012
Source: Centre for Ecological Sciences
Reference: None
Subject: International Journal of Applied Earth Observation and Geoinformation
Keywords: Virtual water, nighttime imagery, Lit area, Urban population, International trade product
Abstract: Freshwater that is consumed in the process of producing a commodity is called virtual water-it represents all water use contained in that commodity. In social systems, water resources can flow when commodities are traded from one region to another. Quantitative monitoring and assessing virtual water flow related to international trade products is an important issue to comprehensively understand the balance of global water resources. In this study we tested the potential of the Defense Meteorological Satellite Program ' s Operationsl Linescan System (DMSP-OLS) nightime images in conjunction with the LandScan population dataset for estimation of virtual water contained in international trade products. Lit area (areal extent of night lights) and urban population were selected as proxies to estimate export virtual water (EVW), import virtual water (IVW), and traded virtual water (TVW) (Summed EVW and IVW), respectively, on the national level. The results showed that IVW can be more accurately estimated than EVW regardless of lit area or urban population. Lit area is normally more appropriate for estimation of the virtual water of developed countries than those of developing countries, but urban population is more appropriate for estimation of the virtual water of developing countries than those of developed countries. Urban population is a better proxy than total population for estimations of virtual water. This study makes a negative finding in that there are relatively large underestimations for developed countries. Another negative finding is that neither lit area nor urban population can be used to estimate net import virtual water (NIVM).
Location: 231
Literature cited 1: None
Literature cited 2: None
ID: 56855
Title: Mapping land subsidence in Jakarta, Indonesia using persistent scatterer interferometry (PSI) technique with ALOS PALSAR
Author: Alex Hay-Man Ng, Linlin Ge, Xiaojing Li, Hasanuddin Z Abidin, Heri Andreas, Kui Zhang
Editor: Freek van der Meer
Year: 2012
Publisher: Elsevier, Vol 18, August 2012
Source: Centre for Ecological Sciences
Reference: None
Subject: International Journal of Applied Earth Observation and Geoinformation
Keywords: Jakarta, land subsidence, displacement, SAR interferometry, Ground water extraction, GPS surveying, persistent scatterer, PSI
Abstract: Jakarta is the capital of Indonesia. It is one of the largest cities with an around 10 million population as for 2010, covering an area of about 661 square kilometers. The land subsidence phenomena in several areas of Jakarta are well known for many years. Land subsidence does damage infrastructures in the city; therefore, it has to be closely monitored and analysed. In this paper, the authors have demonstrated the capability of the PALSAR sensor aboard the Japanese ALOS satellite for large-scale mapping of land subsidence in Jakarta. Mapping results were produced from 17 ALOS PALSAR L-band radar images using persistent scatterer radar ilnterferometry (PSI). The GEOS-PSI software, developed by the Geodesy and Earth Observerving Systems group at UNSW for PSI analysis, was used to detect and map those land subsidence. The results showed that the land in the area of Jakarta was deforming at different rates across several zones. The land subsidence measured from ALOS PALSAR imagery were cross-examined with the subsidence values obtained from 4 GPS campaign surveys by the authors at 19 stations between 2007 and 2010. The magnitudes and trends of the deformation obtained from both techniques agreed well in general for those pinpoints of GPS. After the removal of 2 suspected outliers in GPS measurements, the subsidence rate difference between the two techniques range from -29 to 6 mm/year, with a standard deviation of 9 mm/year and an average absolute difference of 8 mm/year. This research has suggested that PSI with L-band ALOS PALSAR data can be a promising technique to complement the GPS surveying for monitoring land subsidence in super large cities like Jakarta.
Location: 231
Literature cited 1: None
Literature cited 2: None
ID: 56854
Title: Automatic simplication and visualization of 3D urban building models
Author: Jinghan Xie, Liqiang Zhang, Jonathan Li, Hao Wang, Ling Yang
Editor: Freek van der Meer
Year: 2012
Publisher: Elsevier, Vol 18, August 2012
Source: Centre for Ecological Sciences
Reference: None
Subject: International Journal of Applied Earth Observation and Geoinformation
Keywords: Urban buildings, Generalization, urban legibilit, dynamic visualization
Abstract: A high-fidelity and real-time rendering urban building model was implemented through the simplication of 3D building groups. An approach to simplify a single 3D building has been addressed for generating a levels-of-detail (LOD) building model in nearby urban regions. In farther regions, a single-chain cluster was used to collect footprints of neighboring building groups. To effectively merge footprints, the Delaunay triangulation and line simplification were employed. As a result, a coarse LOD model was created based on generalized footprints and building heights. Our approach not only preserved urban legibility (Lynch, 1960), which is effective for viewers visually navigating through an urban environment, but also implemented dynamic visualization of 3D city models.
Location: 231
Literature cited 1: None
Literature cited 2: None
ID: 56853
Title: Urban climate map system for Dutch spatial planning
Author: Chao Ren, Tejo Spit, Sanda Lenzholzer, Hung Lam Steve Yim, Bert Heusinkveld, Bert van Hove, Liang Chen, Sebastian Kupski, Rene Burghardt, Lutz Katzschner
Editor: Freek van der Meer
Year: 2012
Publisher: Elsevier, Vol 18, August 2012
Source: Centre for Ecological Sciences
Reference: None
Subject: International Journal of Applied Earth Observation and Geoinformation
Keywords: Urban Climatic Map System (UCMS), Geographic Information System (GIS), platform, Thermal and wind environment, Compact city, Urban planning
Abstract: Facing climate change and global warming outdoor climatic environment is an important consideration factor for planners and policy makers because improving it can greatly contribute to achieve citizen ' s thermal comfort and create a better urban living quality for adaptation. Thus, the climatic information must be assessed systematically and applied strategically into the planning process.
This paper presents a tool named Urban Climate Map System (UCMS) that has proven capable of helping compact cities to incorporate climate effects in planning processes in a systematic way. UCMS is developed and presented in a Geographic Information System (GIS) platform in which the lessons learned and experience gained from interdisciplinary studies can be included. The methodology of UCMS of compact cities, the construction procedure, and the basic input factors-including the natural climate resources and planning data-are described. Some literatures that shed light on the applicability of UMCS are reported. The Municipality of Arnhem is one of Dutch compact urban areas and still under fast urban development and urban renewal. There is an urgent need for local planners and policy makers to protect local climate and open landscape resources and make climate change adaptation in urban construction. Thus, Arnhem is chosen to carry out a case study of UCMS. Although it is the first work of Urban Climatic Mapping in The Netherlands, it serves as a useful climatic information platform to local planners and policy makers for their daily on-going works. We attempt to use a quick method to collect available climatic and planning data and create an information platform for planning use. It relies mostly on literature and theoretical understanding that has been well practiced elsewhere. The effort here is to synergize the established understanding for a case at hand and demonstrate how useful guidance can still be made for planners and policy makers.
Location: 231
Literature cited 1: None
Literature cited 2: None
ID: 56852
Title: Mapping and analyzing change of impervious surface for two decades using multi-temporal Landsat imagery in Missouri
Author: Bo Zhou, Hong S He, Timothy A Nigh, John H Schulz
Editor: Freek van der Meer
Year: 2012
Publisher: Elsevier, Vol 18, August 2012
Source: Centre for Ecological Sciences
Reference: None
Subject: International Journal of Applied Earth Observation and Geoinformation
Keywords: Impervious surface growth, Sub-pixel classification, Urban and rural sprawl, Missouri
Abstract: Human population growth and associated sprawl has rapidly converted open lands to developed use and affected their distinctive ecological characteristics. Missouri reflects a full range of sprawl characteristics that include large metropolitan centers, which led growth in 1980s, and smaller metropolitan and rrural areas, which led growth in 1990s. In order to study the historical patterns of sprawl, there is a need to quantitatively and geographically depict the extent and density of impervious surface for three time periods, where impervious surface growth was derived as the subtraction of impervious surface mapped from the different time periods. Accuracy assessment was performed by comparing satellite derived impervious surface images with ground-truth acquired from high resolution air photos. Results show that during 1980-2000, 129,853 ha of land were converted to impervious surface. Sprawl was prominent on urban fringe (within the urban boundaries) during 1980s with 23, 674 ha of land converted to impervious surface compared to 22, 918 ha in 1990s. There was a temporal shift in the rural landscapes (outside the urban boundaries) in the 1990s with 48,079 ha of land converted to impervious surface compared to 35, 180 ha in 1980s. Major findings based on analysis of the impervious surface growth include: (i) new growht of impervious surfaces are concentrated on areas with 0.5-1.0% road cover; (ii) most new growths are either inside or close to urban watersheds; and (iii) most new growths are either inside or close to countries with metropolitan cities. This research goes beyond the usual hot spots of metropolitan areas to include rural landscapes where negative impact was exerted to the ecosystem due to the low density development and larger affected areas.
Location: 231
Literature cited 1: None
Literature cited 2: None
ID: 56851
Title: Combining ALOS and ERS-2 SAR data for the characterization of tidal flats. Case study from the Baie des Veys, Normandy, France
Author: Jean-Paul Deroin
Editor: Freek van der Meer
Year: 2012
Publisher: Elsevier, Vol 18, August 2012
Source: Centre for Ecological Sciences
Reference: None
Subject: International Journal of Applied Earth Observation and Geoinformation
Keywords: Advanced Land Observing Satellite (ALOS), European Remote Sensing satellite (ERS-2), Geology, Remote sensing, Rough surfaces, Satellites, Synthetic aperture radar
Abstract: To better understand the SAR backscattering of tidal flats ' sediments, a study was conducted in the framework of the ALOS Date European Node. The approach is mainly based on the analysis of a time series of ALOS data acquired from April to June 2008. The emphasis is on the spatial statistics of the underlying random surface of the tidal flat. Three ALOS cycles with interesting adjacent swath configurations were considered. The study comprised field work to establish the ground truth, and then the analysis of radar data. For this purpose combined PALSAR L-band HH and ERS-2C-band VV data were explored, because dual-frequency data acquisition is needed for geophysical parameters retrieval. Co-polarized data are more relevant for the study of the tidal flat itself, whereas the HV polarization is suitable for identifying the presence of halophytic plants growing in the upper part of the tidal flat. Quad-polarization L-band data could be of great interest, but experiments could not be set up due to lack of suitable acquisitions. The C-band is more accurate for sensing the roughness of the finer sediments, whereas the L-band is more relevant for drawing the instantaneous limit of the sea This paper briefly discusses the role of the local mean time for the study of areas experiencing high tidal range. For the test site located in Normandy, the ALOS acquisition time does not allow more than 55 percent of the tidal flat to be exposed.
Location: 231
Literature cited 1: None
Literature cited 2: None
ID: 56850
Title: Assessment of SAR-retrieved soil moisture uncertainty induced by uncertaintyon modeled soil surface roughness
Author: E De Keyser, H Vernieuwe, H Lievens, J Alvarez-Mozos, B De Baets, N E C Verhoest
Editor: Freek van der Meer
Year: 2012
Publisher: Elsevier, Vol 18, August 2012
Source: Centre for Ecological Sciences
Reference: None
Subject: International Journal of Applied Earth Observation and Geoinformation
Keywords: Soil moisture retrieval, SAR, Uncertainty assessment, Linear regression, Soil surface roughness
Abstract: The Integral Equation Model (IEM) is frequently used to retrieve moisture content of bare soils from synthetic aperture radar (SAR) images. This physically-based backscatter model requires surface roughness parameters, generally obtained by in situ measurements, which unfortunately often result in inaccurately retrieved soil moisture contents. Furthermore, when the retrieved soil moisture contents need to be used in data assimilation applications, it is important to also assess the retrieval uncertainty. Therefore, in this paper a regression -based method is developed that allows for the parameterization of roughness and that provides an estimation of its uncertainty by means of a probability distribution. By further propagating this distribution through the inversion of the IEM, a probability distribution of soil moisture content is obtained. It was found that 70% of the thus obtained distributions are skewed and non-normal. Furthermore, it is shown that their interquartile range varies depending on soil moisture conditions. Compariosn of soil moisture measurements with the retrieved median values of the soil moisture histograms results in a root mean square error (RMSE) of approximately 3.5 vol.
Location: 231
Literature cited 1: None
Literature cited 2: None
ID: 56849
Title: Assessment of pan-sharpening methods applied to image fusion of remotely sensed multi-band data
Author: Yuhendra, IIham Alimuddin, Josaphat Tetuko Sri Sumantyo, Hiroaki Kuze
Editor: Freek van der Meer
Year: 2012
Publisher: Elsevier, Vol 18, August 2012
Source: Centre for Ecological Sciences
Reference: None
Subject: International Journal of Applied Earth Observation and Geoinformation
Keywords: Pan-sharpening, Fusion methods, SVM, Image quality, Noised-based metric
Abstract: Image fusion is a useful tool for integrating a high resolution panchromatic image (PI) with a low resolution multispectral image (MIs) to produce a high resolution multispectral image for better understanding of the observed earth surface. Various methods proposed for pan-sharpening satellite images are examiend from the viewpoint of accuracies with which the color information and spatial context of the original image are reproduced in the fused product image. In this study, methods such as Gram-Schmidt (GS), Ehler, modifed intensity-hue-saturation (M-IHS), high pass filter (HPF), and wavelet-principal componenet analysis (W-PCA) are compared. The quality assessment of the products using these different methods is implemented by means of noise-based metrics. In order to test the robustness of the image quality, Poisson noise, motion blur, or Gaussian blur is intentionally added to the fused image, and the signal-to-noise and related statistical parameters are evaluated and compared among the fusion methods. And to achieve the assessed accurate classification process, we proposed a support vector machine (SVM) based on radial basis function kernel. By testing five methods with WorldView2 data, it is found that the Ehler method shows a better result for spatial details and color reproduction than GS, M-IHS, HPF and W-PCA. For QuickBird data, it is found that all fusion methods reproduce both color and spatial information close to the original image. Concerning the robustness against the noise, teh Ehler method shows a good performance, whereas the W-PCA approach occasionally leads to similar or slightly better results. Comparing the performance of various fusion methods, it is shown that hte Ehler method yields the best accuracy, followed by the W-PCA. The producer ' s and user ' s accuracies of the Ehler method are 89.94% and 90.34%, respectively, followed by 88.14% and 88.26% of the W-PCA method.
Location: 231
Literature cited 1: None
Literature cited 2: None
ID: 56848
Title: Soil-landscape modeling and land suitability evaluation: the case of rainwater harvesting in a dry rangeland environment
Author: Anwar Al-Shamiri, Feras M Ziadat
Editor: Freek van der Meer
Year: 2012
Publisher: Elsevier, Vol 18, August 2012
Source: Centre for Ecological Sciences
Reference: None
Subject: International Journal of Applied Earth Observation and Geoinformation
Keywords: Land use planning, Soil survey, terrain attributes, digital elevation model, watershed, spatial interpolation
Abstract: The arid to semi-arid region is characterized by a scarcity of land and water resources, which threatens the livelihoods of the inhabitants. Rainwater harvesting is an important practice to improve water and land productivity and to cope with climate change in the drier marginal environments. The accurate determination of the location and types of rainwater harvesting interventions through a land suitability assessment is key to successful implementation. However, adequate information about resources is needed. Unfortunately, the arid areas suffer from a scarcity of detailed soil information and preparation of this data is often costly and time consuming. This research examines the utility of modern soil-landscape modeling techniques to provide soil and topographic information that improves land suitability assessment. The suitability of the land for two types of rainwater harvesting-contour ridges and runoff strips-to grow range crops (Atriplex - Atriplex halimus) or field crops (barley-Hordeum vulgare) was examined. Two methods were compared for an area of 26 km2 - spatial interpolation between observations (inverse distance weighted) using 108 points, and a soil-landscape prediction model that used terrain attributes derived from a digital elevation model (DEM). Soil depth was predicted to within + 40 cm for 89% of the field observations and surface stonines was predicted to within + 20% for 82% using the soil-landscape model. The corresponding values using the spatial interpolation model were 81% and 73%. The agreement between the suitability classes derived from field observations and those derived from the soil-landscape prediction model was slightly better than those derived from the interpolation model. Moreover, the spatial distribution of the suitability classification derived from the soil-landscape prediction model shows a more realistic pattern and better identification of extreme land charcteristics, such as rocky areas and deep soils. These results will help in generating reliable suitability maps that support the implementation of sustainable land use alternatives in the arid environment.
Location: 231
Literature cited 1: None
Literature cited 2: None
ID: 56847
Title: A comparison study of impervious surfaces estimation using optical and SAR remote sensing images
Author: Hongsheng Zhang, Yuanzhi Zhang, Hui Lin
Editor: Freek van der Meer
Year: 2012
Publisher: Elsevier, Vol 18, August 2012
Source: Centre for Ecological Sciences
Reference: None
Subject: International Journal of Applied Earth Observation and Geoinformation
Keywords: Impervious surface, ISA, ENVISAT ASAR, Wide Swath Mode (WSM), ANN, SVM
Abstract: The estimation of impervious surface are (ISA) is becoming increasingly important because of its environmental and socio-economic significance. However, accurate ISA estimation remains challenging due to the diversity of impervious materials, as well as the occurrence of clouds in subtropical humid areas. In order to address these challenges and provide an accurate estimation of ISA in cloudy areas, it is advantageous to use both optical and microwave remote sensing which can penetrate cloud coverage. Our study aims to conduct a comprehensive comparison between these two data sources and between different methods for mapping ISA. Both the classification results and accuracy assessment provide a better understanding about the differences between Landsat ETM+ and ENVISAT ASAR images and between artificial neural network (ANN) and support vector machine (SVM) classifier for estimating the impervious surfaces. The comparison demonstrates that ETM+ images alone provide a better ISA estimation (OA: bout 90%; Kappa: about 0.88) than the estimation from ASAR images alone (OA: about 85% ; Kappa: about 0.77). Additionally, the experiment indicates that SVM should be a better choice for ISA estimation using Landsat ETM+ images, while ANN turns out to be more sensitive to the confusion between dry soils and bright impervious surfaces, and between shade and dark impervious surfaces. For ENVISAR ASAR images, ANN gets a better result with higher accuracy, while the SVM classifier produces more noise and has some edge effects.
Location: 231
Literature cited 1: None
Literature cited 2: None
ID: 56846
Title: Emissivity mapping over urban areas using a classification -based approach: Application to the Dual -use European Security IR Experiment (DESIREX)
Author: J A Sobrino, R Oltra-Carrio, J C Jimenez-Munoz, Y Julien, G Soria, B Franch, C Mattar
Editor: Freek van der Meer
Year: 2012
Publisher: Elsevier, Vol 18, August 2012
Source: Centre for Ecological Sciences
Reference: None
Subject: International Journal of Applied Earth Observation and Geoinformation
Keywords: Urban classification, Emissivity maps, Spectral library, TES algorithm, DESIREX
Abstract: In this work a methodology to provide an emissivity map of an urban area is presented. The methodology is applied to the city of Madrid (Spain) using data provided by the Airborne Hyperspectral Scanner (AHS) in 2008. From the data a classification map with twelve different urban materials was created. Each material was then characterized by a different emissivity, whose values were obtained from the application of the TES algorithm to in situ measurements and values extracted from the ASTER spectral library. This new emissivity map could be used as a basis for determining the temperature of the city and to understand the urban heat island effect in terms of spatial distribution and size.
Location: 231
Literature cited 1: None
Literature cited 2: None
ID: 56845
Title: Evaluation of estimating daily maximum and minimum air temperature with MODIS data in east Africa
Author: Shengpan Lin, Nathan. J Moore, Joseph P Messina, Mark H DeVisser, Jiaping Wu
Editor: Freek van der Meer
Year: 2012
Publisher: Elsevier, Vol 18, August 2012
Source: Centre for Ecological Sciences
Reference: None
Subject: International Journal of Applied Earth Observation and Geoinformation
Keywords: MODIS, Land surface temperature, Air temperature estimation, Species distribution model
Abstract: Real time and spatially distributed Ta (air temperature) data are desired for many applications. Ts (land surface temperature) derived from remote sensors has been used to estimate Ta in previous studies. Exploring MODIS Aqua Ts and station measured daily maximum and minimum Ta over east Africa, we found that Ts did not agree well with Ta during the day (MAE (Mean Absolute Error) = 6.9 +5.00C) but had better agreement during the night (MAE = 1.9+1.70C). A stepwise linear regression method was applied to construct possible models to predict Ta based on MODIS data. Our results showed that, only considering elevation, high spatial resolution Ta could be obtained by simpel linear modles, with MAE = 1.90C, agreement index = 0.79 for daily maximum Ta, and MAE = 1.90C, agreement index = 0.92 for daily iminum Ta. MODIS Ts data could provide temporal variation information and slightly improve the accuracy of model predictions (by 0.20 C of MAE). However, considering (i) major absences (about 2/3 of days) of Ts data due to cloud cover and (ii) small Ta variations in time (? = 2.1 0C) over east Africa, modles without Ts might be more practical in particular applications such as tsetse fly distribution models. Other variables including solar zenith angle, low level precipitable water content, and vegetation index (NDVI and EVI) were insignificant in the daily maximum and minimum Ta estimation model after elevation and Ts had already been considered as predictors.
Location: 231
Literature cited 1: None
Literature cited 2: None
ID: 56844
Title: Drought monitoring in Iran using the perpendicular drought indices
Author: Alireza Shahabfar, Abduwasit Ghulam, Josef Eitzinger
Editor: Freek van der Meer
Year: 2012
Publisher: Elsevier, Vol 18, August 2012
Source: Centre for Ecological Sciences
Reference: None
Subject: International Journal of Applied Earth Observation and Geoinformation
Keywords: Drought monitoring, perpendicular drought indices, Remote sensing, droughts in Iran
Abstract: This paper aims at finding, evaluating and refining an appropriate drought estimation method for semi-arid regions, e.g., Iran using remote sensing. Recently developed methods, the Perpendicular Drought Index (PDI) and Modified Perpendicular Drought Index (MPDI), are selected as satellite based drought indices in this study. Time series of the Moderate Resolution Imaging Spectroradiometer (MODIS) images are collected over the region spanning the time interval from February 2000 to December 2005, and the PDI and MPDI are calculated. Then, these indices are evaluated against meterorological drought indices including Z-score (Z), China -Z Index (CZI) and Modified China-Z Index (MCZI) over 180 meteorological observing stations in Iran. The results show that there is a statistically significant correlation between the PDI and MPDI and regional surface dryness and drought conditions. It is further confirmed that the PDI is performing well for bare soil applications or early stages of vegetation growth, while the MPDI is best for vegetated surfaces yet effective for bare soils. Since Iran is characterized by semi-arid or arid climatic conditions, the perpendicular drought indices could be used as simple remote sensing-based drought indices in Iran and in other developing countries with similar climatic conditions.
Location: 231
Literature cited 1: None
Literature cited 2: None
ID: 56843
Title: Estimating regional wheat yield from the shape of decreasing curves fo green area index temporal profiles retrieved from MODIS data
Author: Louis Kouadio, Gregory Duveiller, Bakary Djaby, Moussa El Jarroudi, Pierre Defourny
Editor: Freek van der Meer
Year: 2012
Publisher: Elsevier, Vol 18, August 2012
Source: Centre for Ecological Sciences
Reference: None
Subject: International Journal of Applied Earth Observation and Geoinformation
Keywords: Yield estimates, Regional scale, Green area index, Senescene, Wheat, MODIS
Abstract: Earth observation data, owing to their synoptic, timely and repetitive coverage, have been recognized as a valuable tool for crop monitoring at different levels. At the field level, the close corerlation between green leaf area (GLA) during maturation and grain yield in wheat revealed that the onset and rate of senescence appeared to be important factors for determining wheat grain yield. Our study sought to explore a simple approach for wheat yield forecasting at the regional level, based on metrics derived from the senescene phase of the green area index (GAI) retrieved from remote sensing data. This study took advantage of recent methodological improvements in which imagery with high revisit frequency but coarse spatial resolution can be exploited to derive crop-specific GAI time series by selecting pixels whose ground-projected instantaneous field of view is dominated by the target crop: winter wheat. A logistic function was used to characterize the GAI senescence phase and derive the metrics of this phase. Four regression-based models involving these metrics (i.e., the maximum GAI value, the senescene rate and the thermal time taken to reach 50% of the green surface in the senescent phase) were related to official wheat yield data. The performances of such models at this regional scale showed that final yield could be estimated with an RMSE of 0.57 ton ha-1, representing about 7% as relative RMSE. Such an approach may be considered as a first yield estimate that could be performed in order to provide better integrated yield assessments in operational systems.
Location: 231
Literature cited 1: None
Literature cited 2: None