Geodaysit 2023

Federica Ghilardi

Dott. Federica Ghilardi

PhD Student – SUSTNET
Department of Agricultural, Forest and Food Sciences - DISAFA - University of Torino (Italy)
GEO4Agri Lab - Laboratorio di Geomatica e Telerilevamento Agro-Forestale del DISAFA


Pixel Mixture Issue in Mapping Vineyard Phenology. A Possible Solution Based on Sentinel-2 Imagery and Local Least Squares
Enrico Borgogno-Mondino, Francesco Parizia, Federica Ghilardi, Alessandro Farbo, Filippo Sarvia, Samuele De Petris

Precision viticulture aims to enhance quality standards of wine production by improving vineyard management. In this framework, satellite optical remote sensing has already proved to be effective for mapping vegetation behavior in space and time. These maps, properly processed, are useful to optimize agronomic practices improving wine production/quality and mitigating environmental impacts. Nevertheless, vineyards represent a challenge in this context because grapevine canopies are discontinuous, and the observed reflectance signal is affected by background. In fact, satellite imagery ordinarily provides spectral measures with medium-low geometric resolution (≥ 100 m2). Therefore, spectral mixture between grapevine canopies, grass and soils is expected within a satellite-derived reflectance pixel and not considering this problem can deeply affect deductions based on this data. In this work, Sentinel-2 (S2) NDVI maps (10 m resolution) were computed and compared to the ones obtained from DJI P4 multispectral UAV over a vineyard sizing 1.5 ha and located in Piemonte region (NW Italy). The proportion of row and inter-row (α(x,y) and 1-α(x,y)) within S2 pixel was computed and mapped classifying DJI photogrammetry point cloud. Involving α(x,y) and S2 NDVI values, reversing spectral unmixing system was defined solving for two average endmembers NDVI values (row and inter-row) using a moving window (21x21 pixels) least squares approach. Results were compared at S2 pixel-level to the average ones computed from DJI, showing a MAE of 0.15 and 0.10 of row and inter-row NDVI respectively.

AIT Contribution
Sala Biblioteca @ PoliBa
A Possible Role of NDVI Time Series from Landsat Mission to Characterize Lemurs’ Habitats Degradation in Madagascar
Enrico Borgogno-Mondino, Federica Ghilardi, Samuele De Petris, Valeria Torti, Cristina Giacoma

Deforestation is one of the main drivers of environmental degradation around the world. Slash-and-burn is a common practice, performed in tropical forests to create new agricultural lands for local communities. In Madagascar, this practice affects many natural areas including lemurs’ habitats. Reforestation within natural reserves is desirable combining native species with fast-growing ones, aiming at habitats restoration. In this context, the extensive detection of forest disturbances can effectively support restoration actions, providing an overall framework to address priorities and maximizing ecological benefits. In this work and with respect to a study area located around the Maromizaha New Protected Area (Madagascar), an analysis was conducted based on a time series of NDVI maps from Landsat missions (GSD = 30 m). The period 1991-2022 was investigated to detect location and moment of forest disturbances with the additional aim of quantifying the level of damage and of the recovery process at every disturbed location. It is worth to remind that the Maromizaha New Protected Area presently hosts 12 species of lemurs. Detection was operated at pixel level by analyzing the local temporal profile of NDVI (yearly step). Time of the eventual detected disturbance was found within the profile looking for the first derivative minimum. Significance of NDVI change was evaluated testing the Cebyšëv condition and the following parameters mapped: (i) level of damage; (ii) year of disturbance; (iii) year of the eventual “total” recovery; (iv) rate of recovery. Finally, temporal trends of both forest lost and recovery were analyzed to investigate potential impacts onto local lemurs population and, more in general, to the entire Reserve.

AIT Contribution
Sala Videoconferenza @ PoliBa