针对现有的商业地理信息系统平台难以灵活整合多源影像数据融合使用的问题，深入研究Cesium平台下多种数据源的空间参考差异和瓦片组织规则，针对不同空间参考的瓦片数据源进行混搭设计，提出基于Cesium的多源本地瓦片数据静态和动态加载方案。实验结果表明，单一瓦片数据源加载方案、静态和动态多源瓦片混搭方案的展示效果较好；静态瓦片混搭方案在加载不同空间参考瓦片数据时容易造成变形；动态多源、多空间参考瓦片混搭方案能有效克服变形问题且展示效果佳。本文实现了在开源GIS平台下的多源影像数据的融合使用，为地理信息系统与遥感类项目应用提供了一个低成本、高灵活性的解决方案，具有较为明显的实际应用价值。

Developments and customizations based on open source software have lower costs and higher flexibilities than the large-scale, high-cost, and high-complexity routine maintenance of commercial geographic information system (GIS) platforms that is limited by the function of the system. An increasing number of GIS applications are migrating from commercial platforms to open source GIS platform frameworks. The open source GIS platform facilitates the application of GIS and promotes the rapid development of spatial data management and processing technologies. However, developers may still face the challenge of scenarios of integration or mashup applications of tile datasets from multiple digital map sources in many GIS projects. Therefore, the data source of the base map based on the open source GIS platform must be increased to extend the space and time coverage of the base map in the study area.
Cesium is an open source 3D map engine developed based on the Web Graphics Library with various characteristics, such as cross-platform, cross-browser, 2D/3D integration, and dynamic geospatial data visualization. This library offers a flexible and efficiency base map customization environment for WebGIS applications with low costs. Cesium provides access and loading support for two mainstream spatial references:WGS84 and Web Mercator coordinate systems. On the basis of these considerations, we comprehensively examined the tile data organization mechanisms and spatial reference differences of the Cesium platform and various tile data sources, such as Google maps, Tianditu, and Bing maps. Two types of tile data loading schemes, namely, static and dynamic loading, were designed for the mashup of multi-source tiles with different spatial references. (1) Experiment involving the single data source tile loading scheme illustrated that single data source tiles could be loaded successfully by the two image services, and the createTileMapServiceImageryProvider image service was suitable as a choice of single data source tile loading scheme. (2) The static and dynamic schemes showed favorable visualization effects when tiles from different data sources with the same spatial coordinate system were loaded. (3) The static tile mashup loading scheme could lead to tile image deformation when multi-source tile data with different spatial references were loaded. (4) The dynamic mashup scheme could overcome the deformation problem and shown better visualization effects than the static one when multi-source tile data with different spatial references were loaded.
The proposed method that is based on Cesium and involves different spatial references and multi-source tile data in offline maps, data fusion, and integration applications can be used to extend the base map data source of GIS and remote sensing projects and has evident potential practical application values.