|Left: An aerial photograph of Fort Jay, courtesy of the National Park Service. Right: A view of our resulting 3-D model of For Jay.|
Construction of dense and detailed three-dimensional models of large 3-D structures, such as buildings and their surroundings, can be useful in many fields. These models can allow engineers to analyze the stability of a structure and then test possible corrections without endangering the original. The models can also provide documentation of historical sites in danger of destruction and archaeological sites at various stages of an excavation. With detailed models, professionals and students can tour such sites from thousands of miles away.
To assist with the planning task for 3-D model acquisition, we have developed a two--stage view planning algorithm to automatically decide where to acquire scan data. Our method proceeds in two distinct stages. In the initial stage, the system is given a 2-D site footprint with which it plans a minimal set of sufficient and properly constrained covering views. We then use a 3-D laser scanner to take scans at each of these views. When this planning system is combined with our AVENUE mobile robot, it automatically computes and executes a tour of these viewing locations and acquires them with the robot's onboard laser scanner. These initial scans serve as an approximate 3-D model of the site. The planning software then enters a second stage in which it updates this model by using a voxel-based occupancy procedure to plan the next best view. This next best view is acquired, and further next best views are sequentially computed and acquired until an accurate and complete 3-D model is obtained.
During the Fall of 2006 we brought this robotic system to Governors Island in the City of New York and constructed a model of Fort Jay (pictured above, first as in an aerial photograph, then as a 3-D model).
|AVENUE Mobile Robot navigating the Fort Jay courtyard|
|Fly around of the complete Fort Jay model|