Bird's-eye viewA bird's-eye view is an elevated view of an object or location from a very steep viewing angle, creating a perspective as if the observer were a bird in flight looking downwards. Bird's-eye views can be an aerial photograph, but also a drawing, and are often used in the making of blueprints, floor plans and maps. Before crewed flight was common, the term "bird's eye" was used to distinguish views drawn from direct observation at high vantage locations (e.g. a mountain or tower), from those constructed from an imagined bird's perspectives.
Height above mean sea levelHeight above mean sea level is a measure of the vertical distance (height, elevation or altitude) of a location in reference to a historic mean sea level taken as a vertical datum. In geodesy, it is formalized as orthometric heights. The quantity is called "metres above mean sea level" in the metric system, while in United States customary and imperial units it would be called "feet above mean sea level". Mean sea levels are affected by climate change and other factors and change over time.
Virtual globeA virtual globe is a three-dimensional (3D) software model or representation of Earth or another world. A virtual globe provides the user with the ability to freely move around in the virtual environment by changing the viewing angle and position. Compared to a conventional globe, virtual globes have the additional capability of representing many different views of the surface of Earth. These views may be of geographical features, man-made features such as roads and buildings, or abstract representations of demographic quantities such as population.
NASA WorldWindNASA WorldWind is an open-source (released under the NOSA license and the Apache 2.0 license) virtual globe. According to the website (), "WorldWind is an open source virtual globe API. WorldWind allows developers to quickly and easily create interactive visualizations of 3D globe, map and geographical information. Organizations around the world use WorldWind to monitor weather patterns, visualize cities and terrain, track vehicle movement, analyze geospatial data and educate humanity about the Earth.
