地球信息科学学报 ›› 2018, Vol. 20 ›› Issue (4): 515-522.doi: 10.12082/dqxxkx.2018.170379

• 地球信息科学理论与方法 • 上一篇    下一篇

逆向热力图的绘制方法

王胜开1,2(), 徐志洁2,3,*(), 张健钦1,2, 杜明义1,2   

  1. 1. 北京建筑大学测绘与城市空间信息学院,北京 100044
    2. 现代城市测绘国家测绘地理信息局重点实验室,北京 10044
    3. 北京建筑大学 理学院,北京 100044
  • 收稿日期:2017-08-15 修回日期:2018-02-16 出版日期:2018-04-20 发布日期:2018-04-20
  • 通讯作者: 徐志洁 E-mail:shengkai_bucea@163.com;xuzhijie@bucea.edu.cn
  • 作者简介:

    作者简介:王胜开(1989-),男,河北邢台人,硕士,主要从事交通GIS,地理可视化,虚拟地理环境方面研究。 E-mail: shengkai_bucea@163.com

  • 基金资助:
    国家自然科学基金项目(41771413);国家自然科学基金青年项目(41701473);北京市自然科学基金项目(173053);北京建筑大学校设基金项目(ZF16081、ZF17062)

A Reverse Rendering Method of Heatmap

WANG Shengkai1,2(), XU Zhijie2,3,*(), ZHANG Jianqin1,2, DU Mingyi1,2   

  1. 1. School of Geomatics and Urban Spatial Information, Beijing University of Civil Engineering and Architecture, Beijing 100044, China
    2. Key Laboratory of Modern Urban Surveying and Mapping, National Administration of Geomatics and Geoinfomation, Beijing 100044, China
    3. College of Science, Beijing University of Civil Engineering and Architecture, Beijing 100044, China
  • Received:2017-08-15 Revised:2018-02-16 Online:2018-04-20 Published:2018-04-20
  • Contact: XU Zhijie E-mail:shengkai_bucea@163.com;xuzhijie@bucea.edu.cn
  • Supported by:
    National Natural Science Foundation of China, No.41771413;The Youth Project of National Natural Science Foundation, No.41701473;Beijing Municipal Natural Science Foundation, No.173053;Beijing University of Civil Engineering and Architecture Foundation, No.ZF16081, ZF17062.

摘要:

热力图是对数据的一种直观的表示方法,在空间大数据挖掘和知识发现的研究中具有良好的展示效果。本文研究了一种逆向渲染流程绘制热力图的方法,提出了将渲染器像素映射的地理空间作为计算分析的空间粒度,解决了热力图影响力叠加规则依赖于渲染器机制的缺点。逆向渲染热力图方法使用地理距离与绘制像素结合计算得到分析点缓冲区半径系数和影响力参数,以此来减弱在不同的地图尺度下热力图的形变程度。采用Kapur多级分割算法自动探测图像阈值得到色彩梯度,优化了热力效应的分级展示,在视觉效果上数据特征更加美观清晰。本文通过一组实验进行了验证,数据是由北京市交通委提供的公交IC刷卡记录,提取了其中某一时间段的刷卡数据作为样本,在相同的实验条件下,分别使用基于开源的Leaflet在线地图和Canvas渲染技术2种绘制热力图渲染方法,得到可视化结果后对比分析。在相同的实验条件下,逆向渲染热力图的可视化效果更符合现代的多尺度电子地图需求,更适用于地理空间POI点空间特征可视化。

关键词: 热力图, 数据可视化, 公交客流分析, 逆向渲染, Leaflet地图

Abstract:

As a graphical representation and visualization method, Heatmap has a more visual and comprehensive display effect due to its capability in large spatial data mining and knowledge discovery, compared with standard analysis chart. With the development of big data and multi-scale digital map technology, a static Heatmap has not been able to meet the user requirements and heatmap has begun to turn multidimensional. This paper presents a method of drawing the Heatmap using the reverse rendering process, in which the geographic space mapped by renderer pixels was taken as the spatial granularity in calculation and analysis. This method solved the problem that the influence superposition mode of the Heatmap is much limited by the rendering mechanism. With the improved method, the influence superposition mode can be flexibly selected according to the analysis requirements, and radius coefficient and influence parameter of the analysis point are calculated by combining the geographical distance and rendering pixel to reduce the deformation of heatmap at different map scales. We used the Kapur multi-level segmentation algorithm to automatically detect the image threshold and get the gradient colors, so that the hierarchical display of thermodynamic effect can be optimized and the visual effects on the data can be more beautiful and clear in the map. This method was tested in a group of experiments with bus IC card records provided by Beijing Municipal Transportation Commission. Under the same experiment condition, Heatmaps were derived by using the reverse rendering process method, as well as the standard process method, both based on the leaflet map and Canvas render. The visual results of the two methods were compared and analyzed at different map scales in different locations. It shows that the visualization effects of reverse rendering method can provide more stable details and more comprehensive display of data features under same experiment conditions. This indicates that the proposed reverse rendering method can improve the visualization effect of spatial features of POI (position of interest) points in Heatmap and is more in line with the requirements of modern multi-scale digital map.

Key words: Heatmap, visualization analysis, analysis of bus passenger flow, reverse rendering, Leaflet map