Multi-scale Representation Of Ocean Flow Fields Euler Method With Consideration Of Features

The Euler method is a common drawing method of ocean flow fields.In the electronic map,it is necessary to dynamically simplify or densify the Euler arrow symbols to meet user's multi-scale representation requirement.While sampling data based on scale,traditional equal-interval sampling will cause loss of feature information of flow field;existing basic electronic map is based on continued summary of accumulating experience and repeated practice which lacks support and guidance from the quantitative model.In oeder to realize multi-scale representation of flow fileds,this paper analyzes weight distribution with consideration of flow field features and the key scales of Euler Method based on map load.And then this paper realizes multi-scale representation of ocean flow fields Euler Method with consideration of features.Finally,this paper evaluates the uability of multi-scale representation of ocean flow fields map.Because different points of data in the flow field are of different importance,this paper distributes weights according to points'importance to ensure that the sampling data can express flow fields feature in details as possible.Firstly,this paper come up with distributing weights on the basis of results of feature extraction,spatial autocorrelation analysis and classification analysis.Then this paper uses rough set theory and takes feature region,velocity autocorrelation analysis,flow velocity,flow direction rate autocorrelation analysis and flow direction rate as the conditional attribute to ensure support degree of the conditional attribute to the feature area.Then this paper determines the weight distribution of different attribute through evidence theory.In order to ensure the stability of the flow field Euler method multi-scale representation after simplifying or densifying data and reduce visual hopping caused by scale switching,this paper takes the map load as the evaluation indicator of multi-scale representation of the Euler method.Firstly,this paper chooses the linear symbol calculation method to obtain the map load and analyzes the suitable map load interval by expert scoring method.Then this paper fits the relationship between map load and scale and limits the load by appropriate load interval to obtain the key scale of multi-scale representation of ocean flow fields.This paper summarizes the drawing precision of flow field in different scales.This paper makes the multi-scale map of ocean flow fields according to the weight of data and the resolution of cartographic data under different scales.Compared with the equal interval sampling,the weighting sampling effectively preserves the feature information of the flow field.When the feature region disappeared because of too small scale,this paper uses the fisheye view technology to densify data within feature region which can preserve flow field feature in a small scale.In the end,this paper establishes evaluation mathematical model by multilevel comprehensive evaluation in fuzzy mathematics and evaluates the uability of multi-scale representation of ocean flow fields map by questionnaire.According to the evaluation results,the Euler method flow fields multi-scale representation can preserve the feature of flow field effectively and keep smooth vision switching at arbitrary scales which better than the traditional equal interval sampling flow field mapping method in effectiveness.