Soil moisture is an important part of the soil, which plays a very important role in crop growth and water-saving irrigation. The GPS positioning system grasps the distribution of soil moisture, which provides a scientific basis for differentiated water-saving irrigation. At the same time, accurate water supply is also conducive to improving crop yield and quality.

Moisture is the main factor that determines the dielectric constant of soil. Measuring the dielectric constant of soil can directly and stably reflect the true moisture content of various soils. Using the most popular principle of soil moisture testing in the world-Frequency Domain Reflectance Principle (FDR): The instrument emits a certain frequency of electromagnetic waves, which are transmitted along the probe, and return after reaching the bottom. The output voltage of the probe is detected due to the dielectric of the soil. The change of the constant depends on the water content of the soil, and the water content of the soil can be calculated from the relationship between the output voltage and the water.