Analysis of TerraSAR-X data and their sensitivity to soil surface parameters over bare agricultural fields

• Published in: Remote sensing of environment Vol. 112; no. 12; pp. 4370 - 4379
• Main Authors: Baghdadi, Nicolas, Zribi, Mehrez, Loumagne, Cécile, Ansart, Patrick, Anguela, Thais Paris
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 15-12-2008; Elsevier
• Subjects: Agronomy. Soil science and plant productions; ALOS/PALSAR; Applied geophysics; ASAR/ENVISAT; Biological and medical sciences; Computer Science; Continental interfaces, environment; Earth Sciences; Earth, ocean, space; Engineering Sciences; Environmental Sciences; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Generalities. Biometrics, experimentation. Remote sensing; Global Changes; Hydrology; Internal geophysics; Remote sensing; Sciences of the Universe; Signal and Image Processing; Soil moisture; Surface roughness; TerraSAR-X; ASAR/ENVISAT; Surface roughness; TerraSAR-X; Soil moisture; ALOS/PALSAR; Cultivated field; soil moisture; X band; L band; remote sensing; incidence angle; Edaphic factor; dynamics; Sensitivity; roughness; Ground surface; C band; frozen ground; Parameter; polarization; soils; radar methods; Synthetic aperture radar
• ISSN: 0034-4257; 1879-0704
• DOI: 10.1016/j.rse.2008.08.004

The sensitivity of TerraSAR-X radar signals to surface soil parameters has been examined over agricultural fields, using HH polarization and various incidence angles (26°, 28°, 50°, 52°). The results show that the radar signal is slightly more sensitive to surface roughness at high incidence (50°–52°) than at low incidence (26°–28°). The difference observed in the X-band, between radar signals reflected by the roughest and smoothest areas, reaches a maximum of the order of 5.5 dB at 50°–52°, and 4 dB at 26°–28°. This sensitivity increases in the L-band with PALSAR/ALOS data, for which the dynamics of the return radar signal as a function of soil roughness reach 8 dB at HH38°. In the C-band, ASAR/ENVISAT data (HH and VV polarizations at an incidence angle of 23°)
are characterised by a difference of about 4 dB between the signals backscattered by smooth and rough areas.
Our results also show that the sensitivity of TerraSAR-X signal to surface roughness decreases in very wet and frozen soil conditions. Moreover, the difference in backscattered signal between smooth and rough fields is greater at high incidence angles. The low-to-high incidence signal ratio (Δ
σ°
=
σ
26°–28°/
σ
50°–52°) decreases with surface roughness, and has a dynamic range, as a function of surface roughness, smaller than that of the backscattering coefficients at low and high incidences alone. Under very wet soil conditions (for soil moistures between 32% and 41%), the radar signal decreases by about 4 dB. This decrease appears to be independent of incidence angle, and the ratio Δ
σ° is found to be independent of soil moisture.