Information about different vegetation parameters such as type, biomass, water content and stages of development are important in many contexts. Together with Earth parameters such as soil moisture and composition, vegetation parameters are used as input for global circulation models in connection with climate change studies, for example. These parameters are used on a global scale for modelling and identifying evaporation, desertification, deforestation and the carbon cycle.
At local and regional level, information about vegetation parameters such as type, status etc. is used to predict crop yields, to monitor which crops are grown in the fields and to regulate fertilization and/or irrigation. Monitoring the development and spread of natural vegetation is another important element in environmental monitoring.
Observations from satellites can be used to measure several of the Earth and vegetation parameters mentioned above. Satellite instruments using microwave frequencies, including radar systems, can measure parameters such as soil moisture, vegetation type, vegetation water content, biomass and vegetation structure.
Radar identifies vegetation
A radar device emits a radar signal and subsequently measures the energy pulse reflected by the Earth’s surface or objects on the surface such as buildings, trees or crops. Radar also measures the degree to which the radar wave changes on reflection, this change being different for different objects. In this way it is possible to distinguish different objects from one another, i.e. different crops, types of forest, terrain, lakes etc. Based on such information, it is possible to create a map of a given area and identify different types of objects such as barley fields, coniferous forests and grass fields.
DTU Space is engaged in developing and assessing methods for determining vegetation types and parameters using advanced radar systems, the so-called polarimetric SAR systems (Synthetic Aperture Radar). This often takes the form of national or international projects, where data from own and other airborne radar and satellite systems are used. Currently, several such advanced radar systems are operational aboard satellites and many more are planned for the near future.