Impulse radar — A new sensor for robots

Ground-based robots for agricultural applications are receiving increased attention as labour availability and cost drive interest and uptake. Here we describe a radar method that is suitable for soil moisture measurement from a moving vehicle. We have employed techniques from impulse radar that enable measurement of soil reflection at resolutions smaller than the antenna beam width. We show how the resolution is affected by the radar pulse-width, antenna parameters, radar location and sensing angle. The radar backscatter coefficient is calculated from the radar signals themselves, and demonstrated by measurements taken on wet pasture at different elevation angles. Measurements show that radar backscatter coefficients can be reliably measured at angles up to 60 degrees from the nadir.