Advanced Radar

At SLU, we conduct extensive research on the application of radar in forestry. Radar, specifically synthetic aperture radar (SAR), is an imaging technology that transmits electromagnetic waves from an active sensor via an antenna, which are scattered by objects and then received by the antenna. Radar wavelengths are divided into bands, which correspond to different parts of the electromagnetic spectrum. For forest structures, the P-, L-, C-, and X-bands (with wavelengths from approximately 80 cm to 3 cm) have proven most useful. Unlike laser scanners, radar beams are relatively wide, scatter across multiple objects simultaneously, and employ a side-looking geometry.

Much of our work focuses on how different wavelengths interact with various forest and vegetation types, allowing us to estimate forest properties such as biomass, volume, and height. A common outcome is the production of wall-to-wall maps of forest attributes. Because active SAR sensors use wavelengths capable of penetrating clouds and rain, the data can be updated more frequently than that from laser scanning or optical sensors, with the only limitation being the platform carrying the sensor. We have worked with sensors including ALOS-2 PALSAR-2, TanDEM-X, Sentinel-1, CosmoSkyMed, Radarsat, SAOCOM, LORA, Carabas, and others.

To gain a better understanding of the relationship between radar measurements and forest properties, our research has also extended to the ground level. This approach allows for higher spatial resolution, improved control over weather conditions, and the collection of consistent, long-term time series data. It also facilitates better integration between radar-based research and other sensing technologies.

Part of this research is conducted at the Svartberget Experimental Forest, which features unique infrastructure for forest studies. Key components that make this site exceptional include the BorealScat-2 radar tower—a 50-metre-high tower equipped with a radar system—and the nearby 150-metre-high ICOS tower, which collects air quality and radiation measurements for large-scale forest ecology research. In addition, we collect ground-penetrating radar profiles, drone-based SAR measurements, ground-based and airborne LiDAR, soil moisture data, dendrometer measurements, weather data, and much more from the area.