| Precision agriculture (PA) is a very important direction for agriculture development in 21st Century. PA will promote the change from extensive agriculture to knowledge and technology-based agriculture. In developed countries, PA is considered as a revolution of crop production and management at the threshold of the new millennium. The key principle of PA is implement of variable management measures based on the spatial & temporal variability of the environment and status of crops, and towards a low-input, high-efficiency, sustainable agriculture. The practice of PA includes three aspects: the acquisition of field information, information management and decision-making, variable-rate management. The acquisition of field information is the premise of PA practice. According to the condition of China, this paper mainly studied the technology of field information acquisition and process based on GPS, GIS and virtual instrument. The main contents of this paper include:1) Based on the analysis of the principle of GPS location and output-sentence format, the hardware interface and communication software were developed for OEM GPS receiver and computer to realize GPS-data real-time acquisition by computer. The methods of GPS-data processing and the way to calculate field area using triangle division were put forward in this paper, and the software was programmed to calculate field area through GPS.2) Experiments were done to test the accuracy of four different kinds of GPS receivers. The static tests showed that the Agl32 provided the most accurate locations with 0.3696m errors, the next was MAP330 and GPS25 OEM, and MAP315 was the last. In area measuring, moving way and static way had the same accuracy, and the error of distance and area was less than 5%, so the GPS accuracy could meet the need ofPA.3) According to the characteristics of field information acquisition, we studied and advanced some field sampling methods. Different sampling methods should be used according to the testing requirement. A field information acquisition platform was designed using network distribution structure and module design method. The signals were divided into analogue signals, digital signals and frequency signals; the same signals were acquired through the same module, so the platform has good universality and extensibility.4) A wireless measuring system was developed for field geographicalinformation based on GPS, and this system was composed of GPS receiver, measuring instrument, GPS wireless communication module and computer, using GPS to measure field geographical information and wireless data communication to transfer data. Testing results showed this method was feasible and no restriction of communication distance.5) The method and principle for rapid measuring soil water content were studied, and a rapid measuring instrument was developed for soil water content based on GPS. The testing results showed that the distribution of soil moisture content in filed had great variability, the range of content was between 17.5% to 40.5%. The results also showed that soil water content had different layers in vertical direction, and with the increase of soil depth the soil water content increased first and then decreased. The variability of soil water content could provide basis for precision saving water irrigation.6) Some spatial interpolations for field information were discussed. Inverse Distance Weighted (IDW) method is sensitive to the distance and circle distributions are found around sampling point. IDW is an accurate interpolation method in case of the field information diffused from some center points. The distribution map produced by spline interpolation is smooth, and spline method has good interpolation effect with rapid run speed in case of dense sampling points. Kriging is a good interpolation method when the data distribute abide normal distribution, and Kringing method can analyze interpolation errors. But the calculating speed of Kringing is the lowest and the imitate model shou...
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