The Research Of Calculating Alternative Samples Of Soil Samples In Mobile Environment

The design of soil samples plays a critical role for the inference of soil property maps in digital soil mapping and it also affects the accuracy of the predicted soil property maps.In the course of real-world field soil sampling,soil samples usually are collected at the designated sampling sites by sampling staff.However,as for the complex and uncertain field environment,the real-world geographic environment conditions of the soil samples can not be predicted and the environment of inaccessible sample points are very common.For instance,the designated soil sample locates in the thick brushwood or at the high-valued crop farmland or the filed is too physically stony to sample without damage to the equipment,sampling at the designated coordinates is impractical in this circumstance.The scheme of the design of soil samples may be damaged by the inaccessible samples points which will decrease the accuracy of the soil property map.In this case,the current scholar's solution is trying to solve the above problem by setting a series of backup soil samples for the soil samples.However,all the solutions are static solutions put forward in the process of the design of soil samples in room and can not deal with the unpredictable environment in the field.All in all,the solutions presented above are unable to solve the problem which the inaccessible soil samples bring.In order to solve the above problems which may be encountered in field sampling work,this paper proposes a dynamic method of calculating alternative samples of soil samples in mobile environment.Based on the assumption that the more similar the environment conditions of two sites,the more similar the soil attributes of the two,this paper calculates the environment similarities between the inaccessible sites and the other grids in the study area,then selects the most similar grids as the alternative sample,and finally applies this method in mobile environment so as to realize the dynamic suggestion of the alternative samples.The research contents and conclusions are as below:1.The research of the method of calculating of alternative samplesFirstly,when a certain designated soil sample can not be accessed in field soil sampling work,based on the assumption that the more similar the environment conditions of two sites,the more similar the soil attributes of the two,calculate the environment similarities between the inaccessible sites and the other grids in the study area,then set a similarity threshold value,set a buffer zone centered on the blocked sample and get the candidate samples.Secondly,analyze the spatial representativeness of the candidate samples and select the most representative samples as the alternative samples.Finally,calculate the cost distance between the location of the staff and the alternative samples.Therefore,the sampling staff could select a alternative sample which is easy to find.2.The design of the prototype system of the calculation of the alternative samples.The prototype system consists of the Android mobile client and the server based on the assumption that the more similar the environment conditions of two sites,the more similar the soil attributes of the two.The Android mobile client is used to realize the basic map service,show the alternative samples dynamically,load the soil sample information and interact with soil sampling staff.The server receives data sent by the mobile client and calculates the alternative samples.3.Application and AssessmentWe apply the dynamic method of calculating the alternative samples proposed in this paper in Xuancheng,Anhui province and calculate the alternative samples in real-world field work.Thirty soil samples were designated based on the method of representativeness grade and 30 alternative samples was calculated based on the method proposed in this paper.We compare the relative deviation between the inaccessible sample sites and their alternative samples and predict the soil property maps based on individual predictive soil mapping.The result shows that the relative deviation between the inaccessible sample sites and their alternative samples are very small and the precision of predicted soil property map and the precision of the 30 designated samples are almost the same.In conclusion,using the method proposed by this paper,we can realize the dynamic calculation of the alternative samples when some certain sample points is blocked in field sampling work,and reduce the time and cost of the sample work,increase the sampling efficiency.And the alternative samples have the similar representativeness as the inaccessible sample sites and they have the similar soil property.