Research Article

The Effect of Pre- and Post-Processing Techniques on Tree Detection in Young Forest Stands from Images of Snow Cover Using YOLO Neural Networks

Volume: 10 Number: 2 December 13, 2024
Aleksey Portnov *, Andrey Shubin , Gulfina Frolova
EN

The Effect of Pre- and Post-Processing Techniques on Tree Detection in Young Forest Stands from Images of Snow Cover Using YOLO Neural Networks

Abstract

A neural network model for individual tree detection was developed based on the YOLOv4 architecture, which underwent additional preprocessing and postprocessing steps. The preprocessing step involved expanding the dataset by randomly cutting fragments from images, calculating anchor box sizes using the K-means clustering algorithm, and discarding anchor boxes that were too small a priori. The existing post-processing block of the YOLO architecture was modified by giving more weight to false positives in the error function and using the non-maximum suppression algorithm. Baseline neural networks from the YOLOv4 and YOLOv5 architectures, each in two versions (pre-trained and not pre-trained on the MS COCO dataset), were used for comparison without any additional modifications. In the overgrown experimental field, multi-season aerial copter surveys and ground counts were conducted on several sample plots to gather data. Comparison of multi-season aerial photographs with ground-count data showed that the best images in terms of the percentage of visually identifiable trees were those taken during the snowy season and when there was no foliage. Using these images and some additional images, we manually created a dataset on which we trained and tested neural network models. The model we developed showed significantly better results (2 to 10 times better) on the mAP 0.5 metric compared to the alternatives we considered.

Keywords

Individual tree detection , Convolutional neural networks , YOLO , Pre- and post-processing of data , Aerial photography , Young forest stands

References

  1. Al-Wassai, F.A., Kalyankar, N.V. 2013. Major limitations of satellite images. Journal of Global Research in Computer Science, 4(5):51–59.
  2. Aleksanin, A.I., Kim, V., Morozov, M.A., Fomin, E.V. 2019. Obnaruzhenie rubok otdel'nyh derev'ev po tenyam na osnove snimkov pribora "Geoton" sputnika "Resurs-P" [Detection of individual tree felling by shadows on the basis of images of Geoton instrument of Resurs-P satellite]. Sovremennye problemy distancionnogo zondirovaniya Zemli iz kosmosa, 16(5):174–182. [In Russian]. DOI:10.21046/2070-7401-2019-16-5-174-182.
  3. Alifanov, V.M. 1995. Klyuchevoj uchastok "Pushchino". In: Paleokriogenez i sovremennoe pochvoobrazovanie [Pushchino key site. In: Paleocryogenesis and modern soil formation]. Izdatel'stvo ONTI Pushchinskogo nauchnogo centra Rossijskoj akademii nauk, Pushchino. pp. 95–156. [In Russian].
  4. Ayrey, E., Fraver, S., Kershaw, Jr. J.A., Kenefic, L.S., Hayes, D., Weiskittel, A.R., Roth, B.E. 2017. Layer stacking: A novel algorithm for individual forest tree segmentation from LiDAR point clouds. Canadian Journal of Remote Sensing, 43(1):16–27. DOI:10.1080/07038992. 2017.1252907.
  5. Bartalev, S., Egorov, V., Zharko, V., Loupian, E., Plotnikov, D., Khvostikov, S., Shabanov, N. 2016. Sputnikovoe kartografirovanie rastitel'nogo pokrova Rossii [Land cover mapping over Russia using Earth observation data]. IKI RAN, Moscow. 208 p. [in Russian].
  6. Baumann, M., Ozdogan, M., Kuemmerle, T., Wendland, K.J., Esipova, E., Radeloff, V.C. 2012. Using the Landsat record to detect forest-cover changes during and after the collapse of the Soviet Union in the temperate zone of European Russia. Remote Sensing of Environment, 124:174–184. DOI:10.1016/j.rse. 2012.05.001.
  7. Bennett, G., Hardy, A., Bunting, P., Morgan, P., Fricker, A. 2020. A transferable and effective method for monitoring continuous cover forestry at the individual tree level using UAVs. Remote sensing, 12(13):2115. DOI:10.3390/rs12132115.
  8. Berland, A., Shiflett, S.A., Shuster, W.D., Garmestani, A.S., Goddard, H.C., Herrmann, D.L., Hopton, M.E. 2017. The role of trees in urban stormwater management. Landscape and Urban Planning, 162:167–177. DOI:10.1016/j.landurbplan.2017.02.0 17.
  9. Bochkovskiy, A., Wang, C.Y., Liao, H.Y.M. 2020. Yolov4: Optimal speed and accuracy of object detection. arXiv preprint arXiv:2004.10934. DOI:10.48550/arXiv.2004.10934.
  10. Bohlin, J., Wallerman, J., Fransson, J.E.S. 2012. Forest variable estimation using photogrammetric matching of digital aerial images in combination with a high-resolution DEM. Scandinavian Journal of Forest Research, 27(7):692–699. DOI:10.1080/02827581. 2012.686625.
APA
Portnov, A., Shubin, A., & Frolova, G. (2024). The Effect of Pre- and Post-Processing Techniques on Tree Detection in Young Forest Stands from Images of Snow Cover Using YOLO Neural Networks. European Journal of Forest Engineering, 10(2), 149-159. https://doi.org/10.33904/ejfe.1462335