pTolemy3D is described as 'projects goal is to provide FOSS tools necessary to build your own 3D GeoWeb application. The Viewer application is similar in concept to Google Earth and World WInd Java. Unlike WWJ, there is greater emphasis on the Browser as a platform' and is an app in the Travel & Location category. There are six alternatives to pTolemy3D for a variety of platforms, including Windows, Mac, Online / Web-based, Linux and Android. The best alternative is Google Earth. It's not free, so if you're looking for a free alternative, you could try NASA World Wind or Flash Earth. Other great apps like pTolemy3D are Earth Browser (Paid), Spectator (Free) and Earth View from Google Earth (Free).
Google Earth lets you fly anywhere on Earth to view satellite imagery, maps, terrain, 3D buildings, from galaxies in outer space to the canyons of the ocean. You can explore rich geographical content, save your toured places, and share with others.
World Wind lets you zoom from satellite altitude into any place on Earth. Leveraging Landsat satellite imagery and Shuttle Radar Topography Mission data, World Wind lets you experience Earth terrain in visually rich 3D, just as if you were really there.
Spectator simplifies access to satellite imagery from NASA, ESA and other providers. It gives you access to images archives, but also tracks satellites in real-time to give you information about next image acquisition.