Estimation de la densite des individus avec des images drones dans les ecosystemes Saheliens du Senegal

  • Ramata Talla Département Biologie végétale Université Cheikh Anta Diop de Dakar, Dakar-fann, Senegal Observatoire Homme-Milieux international de Tessékéré, CNRS Université Cheikh Anta Diop de Dakar, Dakar-fann, Senegal
  • Diara Sylla Département Biologie végétale Université Cheikh Anta Diop de Dakar, Dakar-fann, Senegal Observatoire Homme-Milieux international de Tessékéré, CNRS Université Cheikh Anta Diop de Dakar, Dakar-fann, Senegal
  • Ndiabou Faye Département Biologie végétale Université Cheikh Anta Diop de Dakar, Dakar-fann, Senegal Observatoire Homme-Milieux international de Tessékéré, CNRS Université Cheikh Anta Diop de Dakar, Dakar-fann, Senegal
  • Moustapha Bassimbé Sagna Département Biologie végétale Université Cheikh Anta Diop de Dakar, Dakar-fann, Senegal Observatoire Homme-Milieux international de Tessékéré, CNRS Université Cheikh Anta Diop de Dakar, Dakar-fann, Senegal
  • Aly Diallo Observatoire Homme-Milieux international de Tessékéré, CNRS Université Cheikh Anta Diop de Dakar, Dakar-fann, Senegal Departement d’agroforesterie Université Assane SECK de Ziguinchor, Senegal
  • Oumar Sarr Département Biologie végétale Université Cheikh Anta Diop de Dakar, Dakar-fann, Senegal
  • Aliou Guisse Département Biologie végétale Université Cheikh Anta Diop de Dakar, Dakar-fann, Senegal Observatoire Homme-Milieux international de Tessékéré, CNRS Université Cheikh Anta Diop de Dakar, Dakar-fann, Senegal
Keywords: Drone, densité, écosystèmes, Sahel, Sénégal, Ferlo

Abstract

Les nouveaux progrès de la technologie des drones et les capacités de traitement des données ont permis d'obtenir des images de haute résolution et des données tridimensionnelles (3D) qui peuvent être utilisées pour évaluer les attributs des arbres. Cette étude a été menée à Widou thiengoly dans la localité du Ferlo, Nord du Sénégal, avec comme objectif général d’appliquer une approche photogrammétrique pour la mesure de la densité des tiges (tiges/ha) avec des images drones. Une méthode de l’approche arbre basée sur un modèle numérique de hauteur d'une zone d'étude de 10 hectares a été mise en œuvre, ce modèle a été construit à partir d'images obtenues par des drones.  De là, la performance de l'algorithme de détection de l’arbre individuel a été évaluée. Pour chaque parcelle, le nombre d'arbres a été compté manuellement en utilisant l'ortho mosaïque dérivée du drone pour référence. Au total, 92 arbres de référence ont été comptés dans le cadre de cette étude et l'algorithme a détecté 75 arbres, ce qui donne une précision supérieure à 90 % (score F de 0,93). Dans l'ensemble, l'algorithme a manqué 10 arbres (erreurs d'omission) et a faussement détecté 3 arbres (erreurs de commission), ce qui donne un compte total de 88 arbres. Cette étude suggère que l'algorithme de filtrage des maxima locaux combiné avec des tailles de fenêtre optimale, appliqués sur un Modèle Numérique de Hauteur construit par photogrammétrie est capable d’effectuer des comptages d'arbres avec une précision acceptable (F > 0,90) dans la zone sahélienne.

 

New advances in UAV technology and data processing capabilities have made it possible to obtain high resolution images and three-dimensional (3D) data that can be used to assess tree attributes. This study was conducted at Widou thiengoly in the Ferlo locality, northern Senegal, with the overall objective of applying a photogrammetric approach for measuring stem density (stems/ha) with UAV images. A tree approach method based on a digital height model of a 10-hectare study area was implemented, which was constructed from UAV images.  From this, the performance of the individual tree detection algorithm was evaluated. For each plot, the number of trees was counted manually using the drone-derived ortho-mosaic as a reference. A total of 92 reference trees were counted in this study and the algorithm detected 75 trees, giving an accuracy of over 90% (F-score of 0.93). Overall, the algorithm missed 10 trees (omission errors) and falsely detected 3 trees (commission errors), giving a total count of 88 trees.  This study suggests that the local maxima filtering algorithm combined with optimal window sizes, applied on a photogrammetrically constructed Digital Height Model is capable of performing tree counts with acceptable accuracy (F > 0.90) in the Sahelian zone.

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Published
2025-09-07
How to Cite
Talla, R., Sylla, D., Faye, N., Sagna, M. B., Diallo, A., Sarr, O., & Guisse, A. (2025). Estimation de la densite des individus avec des images drones dans les ecosystemes Saheliens du Senegal. European Scientific Journal, ESJ, 45, 274. Retrieved from https://eujournal.org/index.php/esj/article/view/20008
Section
ESI Preprints