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Crop area mapping in West Africa using landscape stratification of MODIS time series and comparison with existing global land products

Vintrou Elodie, Desbrosse Annie, Bégué Agnès, Traoré Sibiry, Baron Christian, Lo Seen Chong Danny. 2012. Crop area mapping in West Africa using landscape stratification of MODIS time series and comparison with existing global land products. International Journal of Applied Earth Observation and Geoinformation, 14 (1) : 83-93.

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Résumé : In Africa, food security early warning systems use satellite-derived data concerning crop conditions and agricultural production. Such systems can be improved if they are provided with a more reliable estimation of the cultivated area at national scale. This paper evaluates the potential of using time series from the MODerate resolution Imaging Spectroradiometer MOD13Q1 (16-day composite of normalized difference vegetation index at 250 m resolution) to extract cultivated areas in the fragmented rural landscapes of Mali. To this end, we first stratified Southern Mali into 13 rural landscapes based on the spatio-temporal variability of NDVI and textural indices, using an object-oriented classification scheme. The accuracy of the resulting map (MODIScrop) and how it compares with existing coarse-resolution global land products (GLC2000 Africa, GLOBCOVER, MODIS V05 and ECOCLIMAP-II), was then assessed against six crop/non-crop maps derived from SPOT 2.5 m resolution images used as references. For crop areal coverage, the MODIScrop cultivated map was successful in assessing the overall cultivated area at five out of the six validation sites (less than 6% of the absolute difference), while in terms of crop spatial distribution, the producer accuracy was between 33.1% and 80.8%. This accuracy was linearly correlated with the mean patch size index calculated on the SPOT crop maps (r2 = 0.8). Using the Pareto boundary as an accuracy assessment method at the study sites, we showed that (i) 20-40% of the classification crop error was due to the spatial resolution of the MODIS sensor (250 m), and that (ii) compared to MODIS V05, which otherwise performed better than the other existing products, MODIScrop generally minimized omission-commission errors. A spatial validation of the different products was carried out using SPOT image classifications as reference. In the corresponding error matrices, the fraction of correctly classified pixels for our product was 70%, compared to 58% for MODIS V05, while it ranged between 40% and 51% for the GLC2000, the ECOCLIMAP-II and the GLOBCOVER.

Mots-clés Agrovoc : télédétection, cartographie, modèle mathématique, terre cultivée, utilisation des terres, sécurité alimentaire, imagerie par satellite, image spot

Mots-clés géographiques Agrovoc : Afrique occidentale, Mali

Classification Agris : U10 - Informatique, mathématiques et statistiques
U30 - Méthodes de recherche
P31 - Levés et cartographie des sols

Champ stratégique Cirad : Axe 1 (2005-2013) - Intensification écologique

Auteurs et affiliations

  • Vintrou Elodie, CIRAD-ES-UMR TETIS (FRA)
  • Desbrosse Annie, CIRAD-ES-UMR TETIS (FRA)
  • Bégué Agnès, CIRAD-ES-UMR TETIS (FRA)
  • Traoré Sibiry, IER (MLI)
  • Baron Christian, CIRAD-ES-UMR TETIS (FRA)
  • Lo Seen Chong Danny, CIRAD-ES-UMR TETIS (FRA) ORCID: 0000-0002-7773-2109

Autres liens de la publication

Source : Cirad - Agritrop (https://agritrop.cirad.fr/561437/)

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