Investigating the Relationship between X-Band SAR Data from COSMO-SkyMed Satellite and NDVI for LAI Detection

Remote Sensing

Fulvio Capodici¹  Guido D’Urso¹ 

[1] Dipartimento di Agraria, Università di Napoli “Federico II”, Via Università 100, I-80055 Portici (NA), Italy; E-Mail:

关键词: Normalized Difference Vegetation Index (NDVI);    LAI;    cross-polarized backscattering;    DEIMOS-1;    COSMO-SkyMed;   

DOI  :  10.3390/rs5031389

来源: mdpi

【 摘 要 】

Monitoring spatial and temporal variability of vegetation is important to manage land and water resources, with significant impact on the sustainability of modern agriculture. Cloud cover noticeably reduces the temporal resolution of retrievals based on optical data. COSMO-SkyMed (the new Italian Synthetic Aperture RADAR-SAR) opened new opportunities to develop agro-hydrological applications. Indeed, it represents a valuable source of data for operational use, due to the high spatial and temporal resolutions. Although X-band is not the most suitable to model agricultural and hydrological processes, an assessment of vegetation development can be achieved combing optical vegetation indices (VIs) and SAR backscattering data. In this paper, a correlation analysis has been performed between the crossed horizontal-vertical (HV) backscattering (σ°_HV) and optical VIs (VI_opt) on several plots. The correlation analysis was based on incidence angle, spatial resolution and polarization mode. Results have shown that temporal changes of σ°_HV (Δσ°_HV) acquired with high angles (off nadir angle; θ > 40°) best correlates with variations of VI_opt (ΔVI). The correlation between ΔVI and Δσ°_HV has been shown to be temporally robust. Based on this experimental evidence, a model to infer a VI from σ° (VI_SAR) at the time, t_{i+ 1}, once known, the VI_opt at a reference time, t_i, and Δσ°_HV between times, t_{i + 1} and t_i, was implemented and verified. This approach has led to the development and validation of an algorithm for coupling a VI_opt derived from DEIMOS-1 images and σ°_HV. The study was carried out over the Sele plain (Campania, Italy), which is mainly characterized by herbaceous crops. In situ measurements included leaf area index (LAI), which were collected weekly between August and September 2011 in 25 sites, simultaneously to COSMO-SkyMed (CSK) and DEIMOS-1 imaging. Results confirm that VI_SAR obtained using the combined model is able to increase the feasibility of operational satellite-based products for supporting agricultural practices. This study is carried out in the framework of the COSMOLAND project (Use of COSMO-SkyMed SAR data for LAND cover classification and surface parameters retrieval over agricultural sites) funded by the Italian Space Agency (ASI).

【 授权许可】

CC BY   
© 2013 by the authors; licensee MDPI, Basel, Switzerland.