Representing time-dynamic geospatial objects on virtual globes using czml-part I: Overview and key issues

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.