Fig. 1. Simulation environment construction and line distribution of the experimental station in Tongzhou, Beijing

Fig. 2. Study area and the location of samples in Quzhou County, Hebei Province

Fig. 3. Flowchart of soil layer identification based on envelope detector and STFT spectrum analysis of ground penetrating radar signals

Fig. 4. Soil layer identification results based on ground penetrating radar by envelope detection in the simulated experimental environment

Fig. 5. Soil layer identification results based on ground penetrating radar by envelope detection in the actual farmland environment

Fig. 6. Relationship between peak weighted value of frequency amplitude and soil relative dielectric constant

Fig. 7. Soil stratification of typical sample sites in study area in Quzhou County, Hebei Province