OBLIQUE PHOTOGRAMMETRY SUPPORTING 3D URBAN RECONSTRUCTION OF COMPLEX SCENARIOS

Accurate 3D city models represent an important source of geospatial information to support various “smart city” applications, such as space management, energy assessment, 3D cartography, noise and pollution mapping as well as disaster management. Even though remarkable progress has been made in recent years, there are still many open issues, especially when it comes to the 3D modelling of complex urban scenarios like historical and densely-built city centres featuring narrow streets and non-conventional building shapes. Most approaches introduce strong building priors/constraints on symmetry and roof typology that penalize urban environments having high variations of roof shapes. Furthermore, although oblique photogrammetry is rapidly maturing, the use of slanted views for façade reconstruction is not completely included in the reconstruction pipeline of state-of-the-art software. This paper aims to investigate state-of-the-art methods for 3D building modelling in complex urban scenarios with the support of oblique airborne images. A reconstruction approach based on roof primitives fitting is tested. Oblique imagery is then exploited to support the manual editing of the generated building models. At the same time, mobile mapping data are collected at cm resolution and then integrated with the aerial ones. All approaches are tested on the historical city centre of Bergamo (Italy)

OBLIQUE PHOTOGRAMMETRY SUPPORTING 3D URBAN RECONSTRUCTION OF COMPLEX SCENARIOS

open9siAccurate 3D city models represent an important source of geospatial information to support various “smart city” applications, such as space management, energy assessment, 3D cartography, noise and pollution mapping as well as disaster management. Even though remarkable progress has been made in recent years, there are still many open issues, especially when it comes to the 3D modelling of complex urban scenarios like historical and densely-built city centres featuring narrow streets and non-conventional building shapes. Most approaches introduce strong building priors/constraints on symmetry and roof typology that penalize urban environments having high variations of roof shapes. Furthermore, although oblique photogrammetry is rapidly maturing, the use of slanted views for façade reconstruction is not completely included in the reconstruction pipeline of state-of-the-art software. This paper aims to investigate state-of-the-art methods for 3D building modelling in complex urban scenarios with the support of oblique airborne images. A reconstruction approach based on roof primitives fitting is tested. Oblique imagery is then exploited to support the manual editing of the generated building models. At the same time, mobile mapping data are collected at cm resolution and then integrated with the aerial ones. All approaches are tested on the historical city centre of Bergamo (Italy).openToschi, I.; Ramos, M. M.; Nocerino, E.; Menna, F.; Remondino, F.; Moe, K.; Poli, D.; Legat, K.; Fassi, F.Toschi, I.; Ramos, M. M.; Nocerino, E.; Menna, F.; Remondino, F.; Moe, K.; Poli, D.; Legat, K.; Fassi, Francesc

MODELLING STEEP SURFACES BY VARIOUS CONFIGURATIONS OF NADIR AND OBLIQUE PHOTOGRAMMETRY

Among the parts of the territory requiring periodical and careful monitoring, many have steep surfaces: quarries, river basins, land-slides, dangerous mountainsides. Aerial photogrammetry based on lightweight unmanned aircraft systems (UAS) is rapidly becoming the tool of election to survey limited areas of land with a high level of detail. Aerial photogrammetry is traditionally based on vertical images and only recently the use of significantly inclined imagery has been considered. Oblique photogrammetry presents peculiar aspects and offers improved capabilities for steep surface reconstruction. Full comprehension of oblique photogrammetry still requires research efforts and the evaluation of diverse case studies. In the present paper, the focus is on the photogrammetric UAS-based survey of a part of a large sandpit. Various flight configurations are considered: ordinary linear strips, radial strips (as the scarp considered has a semi-circular shape) and curved ones; moreover, nadir looking and oblique image blocks were acquired. Around 300 control points were measured with a topographic total station. The various datasets considered are evaluated in terms of density of the extracted point cloud and in terms of the distance between the reconstructed surface and a number of check points

UAV oblique photogrammetry and lidar data acquisition for 3D documentation of the Hercules Fountain

[EN] This paper discusses some enhancements concerning 3D modelling, and the integration and comparison of 3D data from aerial and terrestrial sensors, developed by innovative geomatics techniques around the metric documentation of cultural heritage. In archaeology, it is interesting to deal with the considerable advantages of new multi-sensor approaches for the data acquisition and the management phases in terms of the sustainability (automated acquisition, quickness, precision, time and cost cutting). In particular, Unmanned Aerial Vehicles(UAVs)photogrammetry with the joint use of nadir and oblique cameras can be usefully combined with the large-scale details acquired by the terrestrial Light Detection and Ranging (LiDAR)in vast areas or complex objects, especially in mostly vertical sized objects. Here, we will report the results of an integrated 3D survey in an archaeological context in the Piedmont region of Italy. The Hercules Fountain is located in the gardens of the Venaria Reale (a Savoy Royal Palace included in the UNESCO heritage list) and has witnessed several events and historical phases during the past centuries–from its construction in the 16thcentury to its disuse and decline in the 17thcentury, right up to the 21stcentury when it was eventually brought back to light. The goal of the test is the creation of a3D continuous model of the site for documentation purposes, future consolidation, and enhancement projects finalised fora public promotion. To meet these strategic aims, a terrestrial laser scanning (TLS henceforth) survey has been designed together with multi-flights by a multi-rotor UAV and terrestrial close-range photogrammetry (CRP) acquisition to produce a highly detailed 3D textured model from which we have inferred standard 2D drawings, digital orthoimages, and further 3D products. In conclusion, the entire workflow and the outputs have been compared together to evaluate the effectiveness of each elaboration according to the different goals of the survey.Chiabrando, F.; Spanò, A.; Sammartano, G.; Teppati Losè, L. (2017). UAV oblique photogrammetry and lidar data acquisition for 3D documentation of the Hercules Fountain. Virtual Archaeology Review. 8(16):83-96. doi:10.4995/var.2017.5961SWORD839681

Small Object Detection in 3D Urban Scenes

3D object detection is the core of semantic analysis in 3D urban scenes,but the existing object detection methods mainly focus on large objects such as buildings and roads,while the detection accuracy of these methods for small objects such as street lamps and manhole covers is low.For this sake,a multi-view small object detection method for 3D urban scenes is proposed.It combines the oblique photogrammetry and 3D object localization,to improve the detection accuracy of small objects.Firstly,small objects are detected in the UAV images using a deep neural network.Then,detection results are back projected onto the three-dimensional urban model.Finally,the 3D detection results are obtained by clustering these 3D objects obtained by back projection.Experimental results show that the proposed method can automatically detect small objects such as manhole covers and windows on the large-scale 3D urban model reconstructedby oblique photogrammetry,it is free of spatial occlusion,and has high accuracy and stability compared with object detection on orthophoto maps

Integrated survey for the reconstruction of the Papal Basilica and the Sacred Convent of St. Francis in Assisi, Italy

The Papal Basilica and the Sacred Convent of Saint Francis in Assisi in Italy are characterized by unique and composite particularities that need an exhaustive knowledge of the sites themselves to guarantee visitor's security and safety, considering all the people and personnel normally present in the site, visitors with disabilities and finally the needs for cultural heritage preservation and protection. This aim can be reached using integrated systems and innovative technologies, such as Internet of Everything (IoE), which can connect people, things (smart sensors, devices and actuators; mobile terminals; wearable devices; etc.), data/information/knowledge and processes to reach the wanted objectives. The IoE system must implement and support an Integrated Multidisciplinary Model for Security and Safety Management (IMMSSM) for the specific context, using a multidisciplinary approach. The purpose of the paper is to illustrate the integrated survey for the reconstruction of the considered site that was necessary to obtain all the necessary information to start to set up the considered IMMSSM and the related IoE based technological system

Integrating automated valuation models (AVMs) with valuation services to meet the needs of UK borrowers, lenders and valuers

Lenders traditionally instruct a valuer to conduct a property valuation to support property secured loan decisions. However AVM use for UK residential loan valuations has recently grown rapidly (CML, 2007) raising questions about how the UK valuers’ professional body, the RICS, should respond. The paper reports research funded by the RICS Education Trust and Residential Professional Group, commencing with interviews and a survey examining valuers’ changing roles in residential loan valuation in the UK, including the use of AVMs. Subsequent interviews with lenders and AVM companies explored choices between different valuation and survey levels, including AVMs, and development of AVM tools designed to support valuers. The paper analyses possible approaches to advice, guidance and regulation of AVM use by the UK professional body, drawing on the survey, interviews and a review of other countries’ professional body responses to AVMs. It is the first systematic study of valuers’ current and likely future involvement with automated valuation and their perceptions of it

Close range mini Uavs photogrammetry for architecture survey

The survey of historical façades contains several bottlenecks, mainly related to the geometrical structure, the decorative framework, the presence of natural or artificial obstacles, the environment limitations. Urban context presents additional restrictions, binding by ground acquisition activity and leading to building data loss. The integration of TLS and close-range photogrammetry allows to go over such stuff, not overcoming the shadows effect due to the ground point of view. In the last year the massive use of UAVs in survey activity has permitted to enlarge survey capabilities, reaching a deeper knowledge in the architecture analysis. In the meanwhile, several behaviour rules have been introduced in different countries, regulating the UAVs use in different field, strongly restricting their application in urban areas. Recently very small and light platforms have been presented, which can partially overcome these rules restrictions, opening to very interesting future scenarios. This article presents the application of one of these very small RPAS (less than 300 g), equipped with a low-cost camera, in a close range photogrammetric survey of an historical building façade in Bologna (Italy). The suggested analysis tries to point out the system accuracy and details acquisition capacity. The final aim of the paper is to validate the application of this new platform in an architectonic survey pipeline, widening the future application of close-range photogrammetry in the architecture acquisition process