Probabilistic Model Of Random Encounter In Obstacle Space

Based on probabilistic temporal geography,the encounter between two moving objects are random.When the areas of the potential positions of the two moving objects in a certain time and space are overlapped,then the probability of the two moving objects meeting at this time is relatively large,which also means that we calculate the movement to some extent.The probability distribution of the potential location active area of the object at some point in time can infer the probability that two moving objects will encounter an event at that moment.From the perspective of probability time geography,the probability of encountering two moving objects in different time and space is not exactly the same,so we need to judge the actual situation when we calculate the probability of encountering two moving objects.The known method for calculating the probability of encountering moving objects is based on discrete space and continuous space.In the discrete space,the encounter event is defined as when two moving objects meet at the same time in the same discrete unit,but the method is limited to discrete.It is not suitable for continuous space because of the effect of the size of the grid cell and the position of the grid cell.The calculation result of this method will change with the granularity of the grid cell.In the calculation method,the constraint condition of the distance threshold is introduced,and the condition that the two moving objects meet is that,at a certain moment,when the distance of the two moving objects in the space of the study area is less than or equal to the distance threshold d_meet,they meet.However,this method is limited to the calculation of the ideal geospatial space without obstacles,but the impact of the widespread obstacles on the encounter events is not considered.Therefore,the quantitative analysis of the probability of encounter needs to consider the actual geographical environment.The existing encounter probability algorithm is based on homogeneous space,ignoring various obstacles and their impact on encounter events.On this basis,the paper first introduces the terrain obstacle factor and proposes the encounter event constrained by the obstacle,that is,the distance between the position points of two moving objects at a certain moment in the obstacle space is less than d_meet and there is no intersection between the line of sight and the surface.This is based on the influence of obstacles on visual perception.Using the principle of line-of-sight analysis,the calculation model of the probability of encountering moving objects is established.In this model,note that the obstacle space is also discrete and discrete space is calculated by the grid unit.The line of sight of the two moving objects is a straight line function considering the height of the moving object itself,and the surface is also represented by the surface function.The calculation method of the encounter probability in the obstacle space proposed in this paper.In the case of not considering the influence of obstacles on the encounter event,the calculation method of the encounter probability in the continuous space is supplemented to some extent.The method is more suitable for the realistic simulation environment and data and to provide a quantitative basis for predicting two moving objects and the maximum possible encounter position.Finally,the paper verifies the validity of the model by simulating the spatio-temporal data of two moving objects.The model uses the partial data of the Wuhan Digital Elevation Model（DEM）to calculate the probability distribution of the moving object into its reachable domain by discretizing the DEM model and inverse proportional weight method.And then according to the proposed obstacle space encounter,the probability calculation method calculates the probability of encountering two moving objects and analyzes the spatiotemporal distribution characteristics of these probabilities.