Speaker
Dr
Keith Morrison
(Cranfield University)
Description
At high spatial resolution (<1m) and/or for short wavelengths (i.e. < 3cm) there is a gap in our understanding of the interaction of a radar wave with natural targets over a SAR scene. This information is needed to look to and assess the next generation of EO satellites. Extant scattering models lack either the ability to incorporate the required SAR parameters or are not applicable at high frequencies. Hence there is a need to define a physically robust wave interaction approach that takes into account all the specificities of high resolution / short wavelength SAR imaging. The ESA project SAR Wave INteraction for Natural Targets Over Land (SWINTOL) is designed to address these deficiencies through a combined modelling and experimental study.
Fieldwork was undertaken by Cranfield University to provide the data necessary for model validation and development. SAR and tomographic profiling (TP) imagery were taken of a barley crop over the growing season with Cranfield’s portable outdoor Ground-Based SAR (GB-SAR) system. It comprises a trailer-mounted cherry picker which can provide measurements up to a height of 9m. Wide-area ~30m x 30m SAR images were captured of the scene from full height, in combination with lower height TP measurements. TP is a scheme for providing a detailed map of the vertical backscatter pattern through a crop canopy along a narrow transect directly beneath the along-track direction, whilst side-looking SAR imagery captures coarser sigma-nought measurements.
Fully-polarimetric imagery was obtained across overlapping 6.5GHz bandwidths over the X- and Ku-band frequency range 8-20GHz. Such high bandwidths provide resolutions in the slant range direction at the wavelength scale. With comparable resolutions in the cross-range directions (there are two within a crop canopy volume) in the TP images, it gives the opportunity to see detail at the plant component level. Measurements were made on seven separate dates between 15 April and 31 July. The former corresponded to emergence of the crop, whilst the latter immediately followed harvesting of the crop. Surface roughness characterisation of the soil was made at the start of the season using a 3D optical stereoscopic system. Full bio-geophysical characterisation of the crop and soil was made on each date; a representative square metre of crop was fully described for 3D structure, biomass, and water distribution, along with soil moisture across the scene.
The presentation will detail the measurements made and provide examples of TP and SAR imagery, and provide an comparative assessment of the results in terms of understanding the backscatter in relation to biophysical and radar parameters.
Primary author
Dr
Keith Morrison
(Cranfield University)
Co-authors
Dr
Arnaud Ginestet
(Noveltis)
Mr
Björn Rommen
(ESA)
Dr
Daniel Andre
(Cranfield University)
Jaime Polo Bermejo
(Cranfield University)
