Christos Stentoumis

National Technical University of Athens

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I. Kalisperakis

Technological Educational Institute of Athens

ΛΓ

Λάζαρος Γραμματικόπουλος

University of West Attica

Paraskevi Nomikou

National and Kapodistrian University of Athens

George C. Karras

University of Thessaly

Sotiris Diplaris

Information Technologies Institute

Eftychios Protopapadakis

National Technical University of Athens

Stefanos Vrochidis

Centre for Research and Technology Hellas

Anastasios Doulamis

National Technical University of Athens

Andreas El Saer

University of West Attica

Varvara Antoniou

National and Kapodistrian University of Athens

Cooperative Institutions

National Technical University of Athens

National and Kapodistrian University of Athens

Centre for Research and Technology Hellas

Information Technologies Institute

Technical University of Crete

Institute of Communication and Computer Systems

University of Crete

Aristotle University of Thessaloniki

Pompeu Fabra University

China Philanthropy Research Institute

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DEVELOPING A STRATEGY FOR PRECISE 3D MODELLING OF LARGE-SCALE SCENES FOR VR

The international archives of the photogrammetry, remote sensing and spatial information sciences/International archives of the photogrammetry, remote sensing and spatial information sciences (2020)

Andreas El Saer Christos Stentoumis I. Kalisperakis Paraskevi Nomikou

Abstract. In this work, we present a methodology for precise 3D modelling and multi-source geospatial data blending for the purposes of Virtual Reality immersive and interactive experiences. We evaluate it on the volcanic island of Santorini due to its formidable geological terrain and the interest it poses for scientific and touristic purposes. The methodology developed here consists of three main steps. Initially, bathymetric and SRTM data are scaled down to match the smallest resolution of our dataset (LIDAR). Afterwards, the resulted elevations are combined based on the slope of the relief, while considering a buffer area to enforce a smoother terrain. As a final step, the orthophotos are combined with the estimated Digital Terrain Model, via applying a nearest neighbour matching schema leading to the final terrain background. In addition to this, both onshore and offshore points-of-interest were modelled via image-based 3D reconstruction and added to the virtual scene. The overall geospatial data that need to be visualized in applications demanding photo-textured hyper-realistic models pose a significant challenge. The 3D models are treated via a mesh optimization workflow, suitable for efficient and fast visualization in virtual reality engines, through mesh simplification, physically based rendering texture maps baking, and level-of-details.

Raised-relief map

Orthophoto

Geoinformatics

Level of detail

10.5194/isprs-archives-xliii-b4-2020-567-2020

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Citations (4)

Automatic Transcription of Greek Folk Dance Videos to Labanotation Based on Autoencoders

Communications in computer and information science (2023)

Georgios Loupas Theodora Pistola Sotiris Diplaris Christos Stentoumis Konstantinos Ioannidis

Autoencoder

Motion Capture

10.1007/978-3-031-49212-9_63

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Citations (0)

A MODULAR MOBILE MAPPING PLATFORM FOR COMPLEX INDOOR AND OUTDOOR ENVIRONMENTS

The international archives of the photogrammetry, remote sensing and spatial information sciences/International archives of the photogrammetry, remote sensing and spatial information sciences (2020)

I. Kalisperakis Theodoros Mandilaras Andreas El Saer P. Stamatopoulou Christos Stentoumis

Abstract. In this work we present the development of a prototype, mobile mapping platform with modular design and architecture that can be suitably modified to address effectively both outdoors and indoors environments. Our system is built on the Robotics Operation System (ROS) and utilizes multiple sensors to capture images, pointclouds and 3D motion trajectories. These include synchronized cameras with wide angle lenses, a lidar sensor, a GPS/IMU unit and a tracking optical sensor. We report on the individual components of the platform, it’s architecture, the integration and the calibration of its components, the fusion of all recorded data and provide initial 3D reconstruction results. The processing algorithms are based on existing implementations of SLAM (Simultaneous Localisation and Mapping) methods combined with SfM (Structure-from-Motion) for optimal estimations of orientations and 3D pointclouds. The scope of this work, which is part of an ongoing H2020 program, is to digitize the physical world, collect relevant spatial data and make digital copies available to experts and public for covering a wide range of needs; remote access and viewing, process, design, use in VR etc.

Mobile mapping

Implementation

Sensor Fusion

Structure from Motion

Motion Capture

Scope (computer science)

10.5194/isprs-archives-xliii-b1-2020-243-2020

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Citations (3)

Monocular Camera Fall Detection System Exploiting 3D Measures: A Semi-supervised Learning Approach

Lecture notes in computer science (2012)

Konstantinos Makantasis Eftychios Protopapadakis Anastasios Doulamis Λάζαρος Γραμματικόπουλος Christos Stentoumis

Robustness

Monocular

Implementation

Software portability

10.1007/978-3-642-33885-4_9

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Citations (8)

Autonomous robotic system for tunnel structural inspection and assessment

International Journal of Intelligent Robotics and Applications (2017)

Konstantinos Loupos Anastasios Doulamis Christos Stentoumis Eftychios Protopapadakis Konstantinos Makantasis

Benchmarking

Machine Vision

10.1007/s41315-017-0031-9

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Citations (78)

[Comparative study of the operation of two day's Hospitals in Athens].

PubMed (2014)

J. E. Mantonakis Nicolas A. Karakatsanis E Spilioti I Karanikoli Christos Stentoumis

The present paper describes the preparation for the commencement of services by the University Mental Health Research Institute (UMHRI) Day Hospital and Eginition Day Hospital whose operation (in 1977) signifies the beginning of the Psychiatric Reform in our country. The two units' functional characteristics and the type of offered services are mentioned. Psychotherapeutic, biological and sociotherapeutic approaches are practiced on a daily basis within a framework of Therapeutic Community services. Moreover, relations, similarities and differences among the two day hospitals are pointed out. Special mention is given to the problems and difficulties that these two units faced upon their commencement, which took place at different time periods, set 32 years apart. The lack of legislative framework with regards to the operation of Day Hospitals, the bureaucratic obstacles and the skepticism towards the new treatment approach of patients, were the basic obstacles that had to be overcome in order for the first Day Hospital to become operational in 1977. Licensing and funding were the main obstacles that the creation of UMHRI's Day Hospital faced, although these two units had already been established. Emphasis was placed on the staff's training, which mainly consisted of young professionals and at the social environment's and all those services' (health-care, community etc) attitude, in the specific catchment area (6th Mental Health Sector). The study of patients' characteristics hospitalized in Eginition's Day Hospital throughout its first year of operation (1977-1978) and of patients hospitalized at UMHRI's Day Hospital, also at its first year of operation (2009-2010), showed, among other things, that in both cases, the number of hospitalized male patients is larger than the number of female patients. This constitutes an exception compared to other countries, whereby female patients outnumber male patients in Day Hospitals. Especially at UMHRI's Day Hospital, the number of men is twice the number of women and three times the number of women in the subgroup of patients with schizophrenia. In addition, at Eginition Day Hospital, the men- women ratio is 3:2 in the total number of hospitalized patients and 2:1 in the schizophrenia subgroup. The comparison between the hospitalized patients in Eginition Day Ηospital and UMHRI. Day Hospital brought out the following differences: inpatients at UMHRI's day Hospital were more often older, (x²= 29.52, p=0.0001), unemployed (x²=14.65, p=0.0001) and used public means of transportation more rarely (x²=7.38, p=0.005). No other differences were found in the rest of the sociodemographic variables such as education, marital status, insurance agency, living conditions, traveling time to the day Hospital, referral source, diagnosis of schizophrenia, past hospitalizations. To conclude, it is worth mentioning that the Day Hospital is in a position to treat patients with active psychotic symptomatology, preventing thus their hospitalization on a 24 hour basis.

Bureaucracy

Day hospital

Catchment area

Source

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Creating a Story Map Using Geographic Information Systems to Explore Geomorphology and History of Methana Peninsula

ISPRS International Journal of Geo-Information (2018)

Varvara Antoniou Lemonia Ragia Paraskevi Nomikou Pavlina Bardouli Danai Lampridou

Story maps are used as an interactive tool for communication and information dissemination. A web-based application using story mapping technology is presented to explore the Methana peninsula. This volcanic area is characterized by specific volcanic geoforms, unique flora and rich history. The story map combines maps, narrative texts and multimedia content. The spatial data produce thematic maps created by a Geographic Information System on geological data, historical monuments, biodiversity and hiking paths. The purpose is to highlight the distinguishing characteristics of the Methana peninsula, to enable users to interact with maps, texts and images and to inform professional and non-professional users about the particular aspects of volcanic areas.

Peninsula

Thematic map

Geologic map

10.3390/ijgi7120484

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Citations (28)

Multiple View Stereovision

Christos Stentoumis

10.5040/9781641899444.015

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Citations (0)

AUTONOMOUS ROBOTIC INSPECTION IN TUNNELS

ISPRS annals of the photogrammetry, remote sensing and spatial information sciences (2016)

Eftychios Protopapadakis Christos Stentoumis Nikolaos Doulamis Anastasios Doulamis Konstantinos Loupos

Abstract. In this paper, an automatic robotic inspector for tunnel assessment is presented. The proposed platform is able to autonomously navigate within the civil infrastructures, grab stereo images and process/analyse them, in order to identify defect types. At first, there is the crack detection via deep learning approaches. Then, a detailed 3D model of the cracked area is created, utilizing photogrammetric methods. Finally, a laser profiling of the tunnel’s lining, for a narrow region close to detected crack is performed; allowing for the deduction of potential deformations. The robotic platform consists of an autonomous mobile vehicle; a crane arm, guided by the computer vision-based crack detector, carrying ultrasound sensors, the stereo cameras and the laser scanner. Visual inspection is based on convolutional neural networks, which support the creation of high-level discriminative features for complex non-linear pattern classification. Then, real-time 3D information is accurately calculated and the crack position and orientation is passed to the robotic platform. The entire system has been evaluated in railway and road tunnels, i.e. in Egnatia Highway and London underground infrastructure.

Discriminative model

Visual inspection

10.5194/isprs-annals-iii-5-167-2016

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Citations (28)

An Effective Camera-to-Lidar Spatiotemporal Calibration Based on a Simple Calibration Target

Sensors (2022)

Λάζαρος Γραμματικόπουλος Anastasios Papanagnou Antonios Venianakis I. Kalisperakis Christos Stentoumis

In this contribution, we present a simple and intuitive approach for estimating the exterior (geometrical) calibration of a Lidar instrument with respect to a camera as well as their synchronization shifting (temporal calibration) during data acquisition. For the geometrical calibration, the 3D rigid transformation of the camera system was estimated with respect to the Lidar frame on the basis of the establishment of 2D to 3D point correspondences. The 2D points were automatically extracted on images by exploiting an AprilTag fiducial marker, while the detection of the corresponding Lidar points was carried out by estimating the center of a custom-made retroreflective target. Both AprilTag and Lidar reflective targets were attached to a planar board (calibration object) following an easy-to-implement set-up, which yielded high accuracy in the determination of the center of the calibration target. After the geometrical calibration procedure, the temporal calibration was carried out by matching the position of the AprilTag to the corresponding Lidar target (after being projected onto the image frame), during the recording of a steadily moving calibration target. Our calibration framework was given as an open-source software implemented in the ROS platform. We have applied our method to the calibration of a four-camera mobile mapping system (MMS) with respect to an integrated Velodyne Lidar sensor and evaluated it against a state-of-the-art chessboard-based method. Although our method was a single-camera-to-Lidar calibration approach, the consecutive calibration of all four cameras with respect to the Lidar sensor yielded highly accurate results, which were exploited in a multi-camera texturing scheme of city point clouds.

Ranging

10.3390/s22155576

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Citations (13)