Representing Time-Dynamic Geospatial Objects on Virtual Globes Using CZML—Part I: Overview and Key Issues

Abstract

Cesium Markup Language (CZML) is an emerging specification for the representation and exchange of time-dynamic geospatial objects on virtual globes. The principal focus of CZML is on the definition of time-varying characteristics that are important for applications of geospatial objects, such as changeable positions/extents, graphical appearances, and other geospatial properties. Due to its unique ability to stream massive geospatial datasets, CZML is ideally suited for efficient, incremental streaming to the client in the network environment. Our goal is to explore and outline the overall perspective of CZML as an efficient schema for representing time-dynamic geospatial objects on virtual globes. Such a perspective is the topic of the two present companion papers. Here, in the first part, we provide an overview of CZML and explore two key issues, and their associated solutions, for representing time-dynamic geospatial objects using CZML: one is how to use CZML properties to describe time-varying characteristics of geospatial objects, and the other is how to use CZML to support streaming data. These innovative improvements provide highly-efficient and more reliable supports for representing time-dynamic geospatial objects. The relevant applications, academic influence, and future developments of CZML are explored in a second paper.

Microservice-Based Platform for Space Situational Awareness Data Analytics

“…Cesium [61] is an open-source JavaScript library for world-class three-dimensional (3D) globes and maps based on WebGL and has become the leading 3D WebGIS platform [62,63]. Cesium is capable of merging image layers from different data sources, loading various industrial-grade 3D model formats (e.g., KML, glTF, GeoJSON, and TopoJSON), and supporting open geospatial consortium (OGC) standards.…”

“…CZML is a JavaScript object notation (JSON) format for the description of a time-dynamic graphical scene. It is an effective means for the network-based, real-time, datadriven analysis of dynamic objects in a 3D digital earth [62,63]. In addition to various default properties, CZML also supports custom properties.…”

“…CZML can meet all kinds of data processing needs; especially for stream computation, CZML is ideally suited for incremental streaming to Cesium for the visualization because of its unique ability to stream massive datasets and the storage of property information of different objects in multiple packets. A CZML packet is a collection of name-value pairs, which describe the geometrical, graphical, semantic, and temporal aspects of a single geospatial object [62]. The data volume in a packet depends on the needs; therefore, CZML guarantees the timeliness of each computation and transmission by controlling the data volume.…”

Representing Time-Dynamic Geospatial Objects on Virtual Globes Using CZML—Part II: Impact, Comparison, and Future Developments

“…At present, there are plenty of Google Earth-based applications that utilize KML to create dynamic, interactive displays of geospatial information. However, due to the increasing incompatibility of the Google Earth API with modern web browsers, Google decided to retire the Google Earth API [1,37], and it did not provide any clear alternatives for the established web-based 3D visual globe applications. Therefore, many Google Earth-based applications are facing the problem of transition.…”

“…In recent years, the importance of time-dynamic geospatial objects and their virtual globe-based applications has been rapidly increasing [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. At present, the most favorite schema for describing custom geospatial objects is the Keyhole Markup Language (KML) [16][17][18].…”