Research On Representation Method Of Spatio-Temporal Object Dynamic Line Symbol With Graph Structure

Geographic spatio-temporal data visualization is combined with visual thinking,pattern identification together with computer data storage and processing capabilities.Which expresses the spatial distribution of geographical phenomena,temporal and spatial changes visually with graphing.Visualization of temporal and spatial data has always been an important means of understanding the organizational structure of spatial and temporal data and the expression of geography.Graph is an abstract data structure which can be used as a mathematical model of spatio-temporal relationship.The relationship of graphic structures are the most common relationships in geographic information spatio-temporal data,such as network topology,social network and international trade graphs.Graph structure relationship is based on the topological relation of the network node and the connection and which demonstrate the potential mode relationship of geographic spatio-temporal data directly.Visualization of spatio-temporal objects with graphical features such as visualization of social networks,visualization of population migration is a hot issue in the field of map visualization.The most important feature of the expression method is a combination of geometric characteristics of line symbols(indicates the direction of movement and so on)and visual characteristics of variables to express the change of spatio-temporal object of the graph structure over time.In this paper,the spatio-temporal objects with graph structure is used as the starting point,the main spatio-temporal change types of the spatio-temporal objects with graph structure is analyzed and then based on the structure of data structure the method of spatial and temporal object representation of graph structure is constructed.The temporal and spatial changes of spatio-temporal objects with graph structure features are visualized by using the dynamic map symbol to express the geographical objects that exist in the form of graph structure.The main contributions are as follows:(1)the expression method of spatio-temporal objects with graphic structureAs the basic of spatio-temporal object expression,the spatio-temporal object data types with graph structures are divided into three types:spatial type data,time type data and attribute type data,the change of the spatio-temporal objects with the structural features of the graph is divided into three variations of the attribute change,the time change and the spatial change.The change of the attribute includes the change of the quantity that is the change of the weight of the spatio-temporal objects with the graph structure.And the change of mass(ie,the change of static visual variable).The change of time contains mainly the change of time node and the change of time interval.The change of space is mainly reflected in the change of spatial geometry and the change of spatial geometric position.In this paper,the construction of the expression model at the concept level is carried out by using the visual variables and spatial geometric features of the flow-line symbol.The mainly characteristic of the expression method is to combine the geometric features of the flow-line symbol with the characteristics of the visual variable,and express the temporal and spatial real object relationship.(2)the symbolic rendering algorithm of spatio-temporal objects with graphic structureThe symbolic expression of spatio-temporal objects with graph structure is the symbolization of flow-line symbol.The geometric features of the flow-line symbol are extended by the shape of the symbol,and the shape of the single element structure flow-line symbol is extended into a complex map symbol with the structure of the map structure in combination with the expression method of the spatio-temporal objects with the structural features of the graph.The flow-line symbol is used to express the change of the point-like geographical object,and the basic flow-line symbol is used to express the flow-line symbol.To express the change of the linear geographic entity;the scalable line symbol is used to express the change of the planar geographic entity.With respect to the spatio-temporal data of the original data connection confusion,the combination of the line symbols and the edge bundling algorithm is used in this paper,and the arcs of the space-temporal objects with the same motion direction are clustered which reduce the problem of visual confusion.In this paper,a symbolic rendering algorithm with the spatio-temporal object expression types with graphic structure is proposed which is used to visualize the geographical phenomena.The spatio-temporal objects symbolic algorithm with graph structures can not only use the dynamic line symbols to express the moving direction of spatio-temporal objects.It can also use the weight to reflect the attribute value of spatio-temporal objects of the graph structure.For the structural changes in the structure of spatio-temporal objects,such as merging,splitting and other changes can be expressed visually.Combined with the dynamic map of the expression method,the restrictions of the static map can only express a single state are broken.