Site Prediction |
Stereophotomap and Stereopace for the management of cultral heritage: An example
Stereophotomap is made up of a set of aerial and/or terrestrial photogrammetric blocks and allows surveying and recording of monuments and sites, without any preliminary restitution. It could be considered a 3D evolution of the traditional ortho-photomap.
Sterophotomap can be observed in 3D and appears as a photographic image that contains all the metric information, like a traditional map, in a single 3D reference system.
Stereophotomap can include both aerial and terrestrial images at the same time, in an unique geo-referenced environment. This could be an interesting and powerful tool when the object of interest is an architectonical or historical building inserted in its contest. Stereophotomap represents a new way of recording photogrammetric surveys, separating the different competencies required by a metric survey and its representation.
The Stereophotomap production process follows the standard procedures used in a traditional photogrammetric survey: image acquisition, survey of a control network and photogrammetric triangulation. Digital images can be directly acquired with a digital camera or, indirectly, by using a classical camera and a photo-scanner. The orientation parameters are obtained through photogrammetric triangulation, where a bundle block adjustment procedure is recommended.
Images, orientation parameters and other data are organised in a logic structure through a software named SV Master. At the end of this phase, any operator, even if an unskilled, seek information, measure elements of the object and carry out a historical-artistic analysis.
The sets of images that constitute the Stereophotomap of the Basilica of Assisi are:
All these sets are linked together in photogrammetric blocks and it is possible to navigate inside them without interruptions. The navigation sequence foresees starting from an aerial view, then going down into the square in front of the Basilica and exploring the facade and finally going inside the Basilica for an analysis of the walls and vaults.
- n.1 aerial set
- n.3 façade sets
- n. 11 internal wall sets
- n. 4 vault sets
Figure 1 - Basilica of Assisi - Scheme for the 3D navigation
The resulting drawings obtained by a traditional architectural survey allow measurements of geometric elements (co-ordinates of single points, distances, areas, volumes…) and require a simple ruler as a measuring instrument. In a more modern approach, the results of a survey are recorded in digital form and the required measuring instruments for reading the co-ordinates of the points are appropriate CAD softwares (e.g. Autocad, Microstation, etc.). In the same way, a stereophotomap requires a specific instrument that is suitable for a correct and complete use of this new type of "map": the Stereospace. This allows the user to explore the stereophotomap and "navigate" all over the stereo-models. The user can move freely from aerial to terrestrial 3D views in a single geo-referenced environment, and can easily measure point co-ordinates.
The features of this instruments are: easy movement inside the whole photogrammetric block without problems in passing from model to the next, easy exchange from aerial to terrestrial images, stereoscopic collimation of points even by unskilled operators thanks to the refinement that is offered by the system, calculations of distances, areas and volume and basic procedures for the restitutions of plots, profiles and DEM. Furthermore, the quick and precise measurement of points co-ordinates and the simultaneous vision of different models with different scales and/or epochs are also possible.
Stereospace uses many of the automatic procedures offered by digital photogrammetry in order to obtain maximum efficiency and to foresee its use by unskilled operators. Stereospace is based on low cost PC, equipped with a stereovision device: an active polarised filter on the screen and passive polarised glasses or LCD glasses.
The images should be recorded at 800/1200 dpi resolution in order to obtain a good visualisation of the details. When a model is observed, only the common part of the images (about 70%) is charged in the RAM, saving space for other purposes.
The standard configuration of the PC is:
PIII 750/PIII Processor
- RAM 256 Mb;
- 2 HD 10 Gb each (One hard disk is reserved for software, another one is for image storing)
- Mouse Wheel PS2
- Stereoscopic vision system
- Stereo Ready graphic board
- Monitor with FV ³ 100HZ
- operative System: WinNT 4.0 or more.