TOPICS

The specific topics of the investigation of GAMHer project are:

1. USE OF 3D DATA AS GEOMETRIC DATABASE FOR GIS AND BIM APPLICARIONS (WP1): The project will exploit the integration and interoperability issues of BIM and GIS systems for combined surveying, management and planning projects. Both systems are still independently used in practical applications, whereas a more efficient and combined used is expected at European level to promote collaboration through integrated practices and open standards. It represents a fundamental step towards the creation of a common environment where the different specialists, involved in the project, can share and use geospatial information coupled with architectural/structural models, and viceversa. The work will go through the available open standards for an interoperable BIM/GIS approach, as well as the technical operations, which can be effectively carried out, and those, which will require new specific functions. The geometrical survey from images and laser scans, that provide data at different levels (from the building until the cartographic scale), as well as the availability of existing data, will be taken into consideration for combined BIM/GIS projects. Particular attention will be paid to small and medium building projects that represent the largest part of commercial applications, where existing libraries are available only for specific objects with simple and regular geometry. This will require the development of procedures able to represent the geometric complexity captured modern digital surveying techniques. The analysis will be then extended towards large infrastructures that have a direct impact at the territorial scale, in which digital geospatial information has a primary importance. In this sense, the work will investigate an approach based on multiple levels of detail (LoD).

2. COMPARISON ON THE PHOTOGRAMMETRIC AND STRUCTURE FROM MOTION (SfM) SOLUTIONS BOTH FROM A THEORETICAL AND PRACTICAL POINT OF VIEW BASED ON ALGORITHMS ANALYSIS AND ACCURACY TESTS (WP3): The project will compare the SfM theoretical approach with traditional photogrammetry in order to point out the differences in terms of analytical adopted solutions and statistical possible outputs. The most diffused SfM based platforms give back poor (or nearly null) information about precision and accuracy of the obtained 3D models therefore, one of the main topics will be to extract, from SfM analytic formulations a possible way to estimate the statistical parameters which give to the generated 3D models the necessary information to assess the quality that influence the possibility to correctly use those products as input data for the geometric databases in GIS and BIM platforms. A second approach will be more based on experimental accuracy tests by using set of check points that will be compared with SfM generated 3D models. The accuracy test will be acted on benchmarks furnished by ISPRS as common data sets, which will allow a possible comparison with analogue tests performed by the international research network. This will contribute to an international grown up of knowledge on real advantages and benefits that SfM can give to the metric knowledge.

3. DESIGN OF POSSIBLE INTEGRATION BETWEEN PHOTOGRAMMETRY AND SfM TO OBTAIN AFFORDABLE RESULTS (WP 3): By considering the results obtained in the previous steps, possible scenarios of integration between photogrammetric and SfM solutions could be planned and possibly verified. Photogrammetric external image orientation solutions often required strong approximate values of the unknowns to be estimated. SfM algorithms could give in a short time good approximations usable as starting points for the most statistically affordable photogrammetric solutions. A feasibility design of a platform able to integrate the advantages of the two modelling techniques could be one the possible results that could inspire future research activities. The feasibility of integration between classical photogrammetry and SfM will be inspected by stereoscopic systems. To achieve a higher level of automation, will be furthermore tested some recently developed algorithms used in managing cloud of points derived from airborne LiDAR surveys. The other aspect is related to the use of these products (cloud points / meshes) for new approaches to structural analysis. Some promising tests were already conducted with cloud points derived from terrestrial laser scanning through a new semi-automatic procedure to transform three-dimensional point clouds of complex objects to three-dimensional finite element models. The procedure aims at solving the problem by constructing a fine discretized geometry with a reduced amount of time and ready to be used with structural analysis. To assess the accuracy of the proposed FE model, a linear natural frequency analysis has been performed; results, illustrated by means of computed natural frequencies, show very good agreement. GAMHer project will exploit the potentialities of photogrammetry for this scope and the benefits that can be obtained in respect to scanning when dealing with the radiometric information provided by the images.

4.  DEFINITION OF THE PROPERTIES OF THE IMAGES THAT CAN BE USED FOR A 3D MODELING OF NATURAL AND BUILT OBJECTS (WP 3): The studies and the experimental tests performed in the previous points will allow defining the correct properties of the images, which can be used to obtain 3D models with a known accuracy useful for different applications.
Simple rules to acquire images for 3D modelling will be defined such as: taken distance, used lenses, used camera, base/distance ratios, radiometric and geometric resolutions, basic metric information. Those specifications will allow to update the 3x3 rules already defined in the past by CIPA-HD for digital photogrammetric software management.

5. SETTING UP OF A PLATFORM TO SHARE IMAGES USEFUL TO EXTRACT 3D METRIC DATA (WP 2): The rapid diffusion of IT technologies and devices to acquire images and video and the interesting results obtained by participative actions to share knowledge and experience. Many initiatives are currently on line to collect tourist and personal images that can be classified and used for different purposes. The intention of the research group is to build up a website where interested people can upload images of CH built and natural assets able to be used for the 3D modelling. Basic instructions will be given to the users in order to select which images can be accepted and to drive the users to document them by means of a basic set of metadata and ancillary information. The images will be checked with respect to the possibility to use them for 3D modelling by using photogrammetric and/or SfM approaches and obtained 3D models will be published and shared to the community. The website will be linked to the main national and international initiatives of CH assets documentation and, possibly, to other international similar initiatives. 

6. TEST AND DEFINITION OF THE BEST SOLUTIONS TO TRANSFORM 3D POINT CLOUDS GENERATED BY AUTOMATIC PHOTOGRAMMETRY AND/OR SfM PLATFORM INTO 3D MODELS FOR VIRTUAL AND REAL REPLICAS BY MEANS OF 3D PRINTERS (WP2): Finally the research group will focus the research on the process pipeline that from point cloud (acquired from integrated methodologies and with a particular focus on data obtained from traditional photogrammetry and SfM techniques) leads to digital fabrication of real replicas and reintegration of built architecture for heritage digitization and dissemination. Thanks to the increase in accuracy of current technologies and the reduction in reproduction costs, digital fabrication has been applied in many new contexts, for example in the reproduction of artworks for museum exhibitions or to support Cultural Heritage scholars or restoration. The project is based on the consideration that 3D models are widely used in cultural heritage to create accurate records of individual monuments and buildings as well as complete sites. This is confirmed by relevant projects  (H2020-REFLECTIVE-7-2014: Advanced 3D modelling for accessing and understanding European cultural assets) and on-going activities on heritage digitization and creation of shareable models (Europeana): the focus is the development of new methods and tools for 3D modelling and the analysis of both resources and physical cultural sites going beyond simple digital reconstruction. The models will be able to spread the knowledge of cultural heritage to researchers and citizens. The documentation of cultural assets is a multimedia process addressed through digital representation of shape and  conservation condition of the heritage. Digital models are expected to become the “new” representation so it is necessary to acknowledge the changing role of the digital reconstruction; preservation and conservation now play in the documentation, analysis and dissemination of heritage. In the perspective of a representation “for everybody”, the new development of 3D printings has underlined some problems in the creation of digital models usable for this final aim. In the Geomatics field, 3D printing is one of the possible results of a survey, as the digital and hardcopy traditional drawings. Metric characteristics (as precision and accuracy) of the printed 3D model have to be taken into account and compared with the same characteristics of the digital model obtained from the survey. This is fundamental in order to understand the possible application fields of digital  reproductions: in some cases the copy has to replace the original, when this is not available anymore (as in Gravitate or Scan4Reco project, within the H2020-REFLECTIVE-7-2014); in other cases copies can efficiently replace an existent piece if this has to be preserved or its fruition has to be limited to the simple exhibition. The model, whose metrical characteristics will have been verified, will be used for example when a tactile exploration will be needed: we are referring to exhibitions meant for children or visually impaired.