Timetag web11/30/2022 Prominent examples of time-dynamic geospatial objects are satellites, aircraft, cars, ships, wild animals, mobile subscribers, meteorological disasters, forest fires, land cover, snow coverage in mountains, and tectonic plates. With the recent technological advances in geospatial information acquisition, such as global navigation satellite systems (GNSS), remote sensing (RS), mobile computing, and sensor networks, the number of time-dynamic geospatial objects and their applications in various disciplines are steadily increasing. It is well known that the Earth is three-dimensional and rapidly changing over time. One of the current main limitations of KML is the lack of advanced capability and necessary flexibility in representing time-dynamic geospatial objects. While KML has proven to be quite useful for representing geographical maps and spatially-based geographical information, there remain several serious limitations when using KML to interact with geospatial objects in a virtual environment. These applications primarily use KML to generate geographic annotations and visualizations on 3D virtual globes. In the few years since the approval of the OpenGIS KML 2.2 Encoding Standard (OGC KML 2.2) in 2008, KML has found numerous applications in several branches of geoscience, including geology, geophysics, geochemistry, climate change, weather forecasting, natural disaster management, and online education games. Due to the authority and broad scope of applications, KML has become widely used for representing geospatial objects in the geoscientific environment, allowing spatially-based objects to be distributed, visualized, and analyzed in one seamless virtual globe interface. Using KML, scientific users can easily create dynamic, interactive displays on virtual globes. As an open standard authorized by the Open Geospatial Consortium (OGC), KML allows users to define how, where, and when custom objects are displayed or animated. Among them, Keyhole Markup Language (KML), an XML-based encoding schema, was adopted by nearly all major virtual globes as the dominant data format for describing custom geospatial objects. At present, there are plenty of universal standards/specifications for the representation and exchange of geospatial objects, such as GML, CityGML, and 3D Portrayal Service. They also offer users an open framework for efficiently describing, displaying, and understanding their own geospatial objects in exquisite detail. The primary reason for virtual globes’ success is that they provide more than just a digital replica of the Earth’s surface with high-resolution images and terrain data. A number of sophisticated and powerful virtual globes, such as Google Earth, NASA World Wind, Cesium, and other online Earth browsers, have been developed and, subsequently, accepted by Earth scientists from different subject fields as convenient platforms to conduct studies, exchange ideas, present results, and share knowledge with a global perspective in a natural and intuitive way. Over the past two decades, virtual globes have become a standard way to integrate, visualize, and analyze multidisciplinary geospatial information at both local and planetary scales. The relevant applications, academic influence, and future developments of CZML are explored in a second paper. These innovative improvements provide highly-efficient and more reliable supports for representing time-dynamic geospatial objects. #Timetag web how toHere, 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. Such a perspective is the topic of the two present companion papers. 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. 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. 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. Cesium Markup Language (CZML) is an emerging specification for the representation and exchange of time-dynamic geospatial objects on virtual globes.
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