In recent times we are witnessing a steep increase in the availability of data coming from real–life environments. Nowadays, virtually every one connected to the Internet may have instant access to a tremendous amount of data from satellite elevation maps, airborne time-of-flight scanners and digital cameras, street–level photographs and even cadastral maps. As for other more traditional types of data such as documents, pictures and videos, users of digital exploration softwares expect commodity hardware to exhibit good performances for interactive purposes, regardless to the size of these data.
In this thesis we propose novel solutions to the problem of rendering large terrain and urban models on site and remotely on commodity platforms. Our solutions build on the concept of multiresolution representation, where alternative representations of the same data with different accuracy are used to selectively distribute the computational power, and consequently the visual accuracy, where it is more needed on the base of user's point of view. In particular, we will introduce an efficient multiresolution data compression technique for planar and spherical surfaces applied to terrain data which is able to handle huge amount of information at a planetary scale. We will also describe a novel data structure for compact storage and rendering of urban entities such as buildings to allow real–time exploration of cityscapes from a remote online repository. Moreover, we will show how recent technologies can be exploited to transparently integrate virtual exploration and general computer graphics techniques with web applications.