Abstract
Abstract. For a long time people have been interested in the past and history and how we can go back in time using a time machine. And while we cannot invent a time machine, at least not yet, we can create a virtual one. Our “virtual” time machine is an interactive web application that allows users to browse through and navigate within historical images (aerial/terrestrial photographs or postcards) that are projected on a 3D photogrammetric model (point cloud or 3D mesh), thus going back in time and interacting with historical 3D models and images. This was achieved by adopting a semiautomatic approach where the user identifies first 6 to 8 hints on the historical image and the photogrammetric model, then this information is used as an entry data to a photogrammetric software that computes the pose and orientation of the image. The purpose of this work, which is part of the ALEGORIA project, is to preserve cultural heritage, to give the users the opportunity to go back in time and study history of a place or simply discover how their hometown looked some years ago.
Highlights
This work is part of the ALEGORIA project that aims at facilitating the promotion of iconographic institutional funds collections describing the French territory in various periods going from the interwar period to our days
The term space resection is the name given to the process in which the spatial position and orientation of photograph is determined based on photogrammetric measurements of the images of ground control points appearing on the photograph (Moffitt and Mikhail, 1980)
We used a historical postcard of the Chambord Castle in France (Figure. 2a) that we succeeded in georeferencing using a set of 6 control points acquired by pointing certain details on the postcard and their correspondents on the point cloud (Figure. 2b)
Summary
This work is part of the ALEGORIA project that aims at facilitating the promotion of iconographic institutional funds collections describing the French territory in various periods going from the interwar period to our days. Contrary to the well anchored exploitation which is made of the satellite imagery where the professional practices are many (researchers, institutions and local authorities) and the data well identified and indexed, the promotion of those collections remains confidential and scattered They are spread within various institutions, digitized partially, generally not or little documented and weakly georeferenced. They represent a rich heritage, little known by the general public and exploited in a way forced by their main users (researchers, institutions and local authorities), in direct consultation at the library or by means of online classic libraries The development of such a heritage would benefit from tools allowing to automate their collection, to be capable of crossing them and of studying them better. The space resection makes use of image coordinates and heavily weighted or fixed object space coordinates to determine the positional and rotational elements of a photograph, or of a camera. The process requires approximated initial values of the unknown parameters, some of which must be estimated by another least squares solution
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