Introduction
The GES DISC, located at Goddard Space Flight Center in Greenbelt, Maryland, is one of several NASA Earth Science data archive centers, primarily archives satellite data related to precipitation, hydrology (Nadeau, et al. 2006), hurricanes, atmospheric chemistry, and atmospheric dynamics. It aims to maximize use of satellite data from numerous satellites and field programs.
Scientists at the GES DISC are familiar with the recent advent of “virtual globes”, such as NASA World Wind (NASA 2008a), Google Earth (Google 2008), Microsoft Virtual Earth (Microsoft 2008), ArcExplorer (ESRI 2008), and others. These virtual globes can integrate satellite imagery, aerial photography, and digital maps and present a three-dimensional interactive representation of data on a global scale.. Especially, “NASA has released World Wind as an open source program to improve its quality through peer review, maximize awareness and impact of NASA research, and increase dissemination of World Wind in support of NASA's mission” (NASA 2008a). It provides, in default, lots of NASA Earth science data from such missions as Landsat 7, the Shuttle Radar Topography Mission, and the Moderate-resolution Imaging Spectroradiometer (MODIS). However, better support for Keyhole Markup Language (KML) makes Google Earth very popular and widely accepted by professionals and public. For this reason, Google Earth was selected to augment the value of geospatial data at NASA GES DISC. Virtual globe systems can be used to discover, add, and share information about any subject in the world that has a geospatial element (Nature 2006). These systems also enable researchers to conveniently collaborate and share their research projects and results. There is renewed hope that every sort of information on the state of the planet, from the levels of toxic chemicals to the incidence of disease will become available to all with a few moves of the mouse (Butler 2006). With the emergence of Web 2.0 and 3.0, research and applications are moving from local machine-based environments to online web-based platforms. Thus, virtual globes are recognized as an important trend in geoscience research and applications.
For the last few years, virtual globes, notably Google Earth, have been used for research and applications in areas such as global climate change (Burek, et al. 2007), weather forecasting (Travis, et al. 2006), natural disasters, conservation of the environment (NIEES 2006), travel, nature, people and culture, history illustration, presidential elections, avian flu (Nature 2006), online game, etc. Most applications involve flat geospatial data and socio-economic data. They are displayed in a virtual globe using geographic elements. The hurricane portal (Leptoukh 2006), implemented and maintained by the GES DISC, uses data derived from NASA remote-sensing instruments to study and visualize hurricanes. More descriptions for other researches and literatures can be found in ‘Related research and discussion’ section of the paper.
In this paper, several solutions are proposed to augment the value of distributed geospatial data based on Google Earth. These solutions cover most of current available methods used in Google Earth for two-dimensional (2D) and three-dimensional (3D) geospatial data. In particular, a new method is proposed here to render vertical geospatial data into vertical orbit curtains in Google Earth. The resultant orbit curtains make vertical geospatial data viewable, transparently or opaquely, in Google Earth. Using our method, 3D geospatial data can be combined and compared with other simultaneously displayed data to facilitate scientific research, create new insights, and improve public understanding of our planet.. Vertical geospatial data derived from satellite CloudSat, Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO), and the Aqua and 2D flat geospatial data from Tropical Rainfall Measurements Mission (TRMM) and Aqua satellite are rendered in Google Earth to provide a basis for synergistic research of Earth science.