How TerraSar-X Quadpol Data can help describing canopies? A comparison to Rapideye multispectral vegetation indices

Kurzfassung

For monitoring of crops in tropical regions satellite SAR data are essential. Only few cloudless days per year hinder the use of optical data. In the microwave region of the electromagnetic spectrum, intensity of energy scattered by vegetation is primarily a function of canopy architecture, dielectric properties, and cropping characteristics, while the visible and infrared energy reflected by vegetation is related to plant pigmentation, internal leaf structure, and leaf/canopy moisture. The TerraSAR-X satellite operates basic imaging modes with different swath widths, resolutions and polarisations. Adjacent to that, the Quadpol experimental mode delivers full polarization capacity (HH, VV, VH and HV). This study analyses the potential of TerraSAR-X Quadpol data for estimating crop canopy parameters by comparing to a RapidEye image of same region and time. We analyzed to which extent different polarizations are correlated to the respective vegetation index using pixel- and object-based comparison approaches. The study highlights potentials and limitations of high resolved X-band SAR data and the full polarization capacity for estimating plant physiological parameters in a region dominated by rice cropping. The study region has been within the Mekong Delta in Vietnam, one of the worlds most prone areas to climate change potentially yielding in increasing natural hazards and dearth prevention. Food security is therefore a major task in Vietnam’s most productive rice growing region. For doing so, knowledge about actual acreage, cropping system and yield estimation is required which for large areas can only be assumed by satellite-based SAR remote sensing.