Geomatics

STANDORT

by Piyush Shah

The most pressing need facing Disaster managers during the immediate aftermath of a disaster is to estimate the impact... more The most pressing need facing Disaster managers during the immediate aftermath of a disaster is to estimate the impact of the disaster on the local population to determine where first-responders should focus rescue efforts. This problem requires an awareness of the scale and scope of the disaster as well as the ability to know where response resources are located, what their capabilities are, and what routes are available for them to take to those who need their help. Solve this problem by developing such a system which will guide Authority taking decision in real time.

Network RTK and Reference Station Configuration

by Mattia De Agostino

Co-authored with Paolo Dabove, published in 'Inside GNSS' on December, 2011.

What effect does network size have on NRTK positioning?
What is the effective distance between reference stations... more What effect does network size have on NRTK positioning?
What is the effective distance between reference stations that enables the precision required for real-time positioning, using multi-frequency, multi-constellation receivers? Also, how does the position accuracy change with increasing distances between CORS?

We carried out some experiments to answer these questions.

Spatial research and geomatic resources applied to the archaeology of the Farafra Oasis

by Fabiani Ulisse

- SPATIAL RESEARCH AND GEOMATIC RESOURCES APPLIED TO THE ARCHAEOLOGY OF THE FARAFRA OASIS (WESTERN DESERT, EGYPT) -... more - SPATIAL RESEARCH AND GEOMATIC RESOURCES APPLIED TO THE ARCHAEOLOGY OF THE FARAFRA OASIS (WESTERN DESERT, EGYPT) - Archaeological research in the desert areas of North Africa has long employed multidisciplinary field and laboratory methods. Increasingly, high precision instruments for mapping archaeological sites and surrounding landscapes over large areas have been used. The Italian Archaeological Mission in the Farafra Oasis - Egypt (IAMFO) of the Sapienza University of Rome benefits from three decades of experience during which it has kept pace with the latest developments in fieldwork techniques. Geomatic techniques, as used by the Area di Geodesia e Geomatica of the same university, are particularly important for archaeological research concerned with large geographical areas, althoughinnovative approaches appropriate for the scale of the work need to be used. This paper will show how survey work was organised in a number of stages, from the creation of accurate maps, to photoplans of significant structures and to DEMs of the different locations of finds. Processing the cartographic data from the Wadi el Obeiyid, moreover, made it possible to hypothesize which areas would have been suitable for human settlement, and these will form the focus of future surveys.

Standardization of Geomatics Applications In Cultural Heritage

by Mohsen Miri

GM2100 Synthesis project

by Efstratios Tsompanopoulos

REMOTE MONITORING OF A LANDSLIDE USING AN INTEGRATION OF GB-INSAR AND LIDAR TECHNIQUES

by Dario Piatti

The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B1. Beijing 2008

Landslide monitoring activities are of paramount importance for landslide hazard and risk assessment. They allow... more Landslide monitoring activities are of paramount importance for landslide hazard and risk assessment. They allow predictions to be
made of the phenomenon evolution which can be used to define risk scenarios, especially when urban areas and infrastructures are
involved. Over the last decades, spaceborne and, more recently, ground-based interferometric synthetic aperture radar (GB-InSAR)
have been successfully used to identify and classify landslides. Ground-based synthetic aperture radar (GB-SAR) interferometry has
already been recognized as a powerful tool, that can be considered complementary or alternative to spaceborne SAR interferometry
for terrain monitoring and to detect structural changes in buildings.
Terrestrial laser scanning (TLS) is a technique increasingly used in remote sensing of unstable slopes. Detailed digital models of the
observed surface are generated with centimetric resolution. In particular, if multitemporal scans of the same area are performed, these
scans can be compared in order to obtain displacement fields.
Both GB-SAR and TLS observations were planned at the end of July 2007 and at the end of October 2007 in order to assess the
hazard of a quarry that is subject to ground instabilities (the Ex-Locatelli quarry near the Baveno village in the Italian Alps on Lake
Maggiore). This paper reports on these measurement campaigns and on a test site set up in Florence (Italy) and discusses the
advantages of the combined use of these innovative techniques. The availability of radar and laser data at the same time has allowed
a comparison to be made of the two techniques and has provided an effective validation test for both.

INTEGRATED DIGITAL TECHNOLOGIES TO SUPPORT RESTORATION SITES A NEW APPROACH TOWARDS A STANDARD PROCEDURE

by Dario Piatti

VSMM 2008 Digital Heritage – Proceedings of the 14th International Conference on Virtual Systems and Multimedia

LIDAR data integrated with digital photogrammetry today represents one of the most attractive ways of facing the... more LIDAR data integrated with digital photogrammetry today represents one of the most attractive ways of facing the metric surveying
of  an  architectural  object. Many  papers  have  illustrated  the  possibility  of  building  a  complete  3D  model  using  just  these  two
techniques.  In  practice,  not many  restorers  are  used  to managing  3D models  and  traditional  graphic  results,  such  as  plans  and
sections,  are  usually  required. The  paper  defines  a  correct  balance  between  the  use  of  traditional  (manual  and  total  station)  and
innovative  (LIDAR and digital photogrammetry)  techniques  in order  to satisfy  the usual  requirements  for  the metric survey of an
architectural object. A project was  carried out  to obtain knowledge of  a Church  in Turin;  it was necessary  to prepare  the  survey
graphic drawings that would be used for the restoration both of the decorative motives and of the structure of the church. The most
important aspect of  this work  is  the  integration of  traditional  topographic  techniques with  the LIDAR  technique. This  integration
was necessary because of the complexity of the object that was to be surveyed and of the requested short times necessary to realize
the survey. The  tools  implemented  in  the new Sir-IO software  (realized by a DITAG  research group of  the Politecnico di Torino)
were of great help  in  this work. Thanks  to  this software  it was possible  to directly plot the details that were to be surveyed on the
realized solid images and orthophotos, thus making the preparation of the survey graphic drawings considerably easier.

NEW SENSORS FOR CULTURAL HERITAGE METRIC SURVEY: THE ToF CAMERAS

by Dario Piatti

XXIIIth International CIPA Symposium (To be published)

ToF cameras are new instruments based on CCD/CMOS sensors which measure distances instead of radiometry. The resulting... more ToF cameras are new instruments based on CCD/CMOS sensors which measure distances instead of radiometry. The resulting point clouds show the same properties (both in terms of accuracy and resolution) of the point clouds acquired by means of traditional LiDAR devices.
ToF cameras are cheap instruments (less than 10.000 €) based on video real time distance measurements and can represent an interesting alternative to the more expensive LiDAR instruments. In addition, the limited weight and dimensions of ToF cameras allow a reduction of some practical problems such as transportation and on-site management.
Most of the commercial ToF cameras use the phase-shift method to measure distances. Due to the use of only one wavelength, most of them have limited range of application (usually about 5 or 10 m).
After a brief description of the main characteristics of these instruments, this paper explains and comments the results of the first experimental applications of ToF cameras in Cultural Heritage 3D metric survey.
The possibility to acquire more than 30 frames/s and future developments of these devices in terms of use of more than one wavelength to overcome the ambiguity problem allow to foresee new interesting applications.

Sensors for 3D Imaging: Metric Evaluation and Calibration of a CCD/CMOS Time-of-Flight Camera

by Dario Piatti

Sensors, 2009

3D imaging with Time-of-Flight (ToF) cameras is a promising recent technique which allows 3D point clouds to be... more 3D imaging with Time-of-Flight (ToF) cameras is a promising recent technique which allows 3D point clouds to be acquired at video frame rates. However, the distance measurements of these devices are often affected by some systematic errors which decrease the quality of the acquired data. In order to evaluate these errors, some experimental tests on a CCD/CMOS ToF camera sensor, the SwissRanger (SR)-4000 camera, were performed and reported in this paper. In particular, two main aspects are treated: the calibration of the distance measurements of the SR-4000 camera, which deals with evaluation of the camera warm up time period, the distance measurement error evaluation and a study of the influence on distance measurements of the camera orientation with respect to the observed object; the second aspect concerns the photogrammetric calibration of the amplitude images delivered by the camera using a purpose-built multi-resolution field made of high contrast targets.

Integration between calibrated Time-of-Flight camera data and multiimage matching approach for architectural survey

by Dario Piatti

SPIE Europe Remote Sensing 2010

In this work, the integration between data provided by Time-of- light cameras and a multi-image matching technique for... more In this work, the integration between data provided by Time-of- light cameras and a multi-image matching technique for metric surveys of architectural elements is presented. The main advantage is given by the quickness in the data acquisition (few minutes) and the reduced cost of the instruments. The goal of this approach is the automatic extraction of the object breaklines in a 3D environment using a photogrammetric process, which is helpful for the final user exigencies for the reduction of the time needed for the drawing production. The results of the performed tests on some architectural elements will be reported in this paper.

UAV and RPV systems for photogrammetric surveys in archaelogical areas: two tests in the Piedmont region (Italy)

by Dario Piatti

Journal of Archaeological Science

Aerial photogrammetric surveys are usually expensive and the resolution of the acquired images is often
limited.... more Aerial photogrammetric surveys are usually expensive and the resolution of the acquired images is often
limited. For this reason, different innovative systems have been developed and tested in order to perform
a photogrammetric survey in an inexpensive way, with high-resolution images. In this context, one of the
most promising acquisition techniques is represented by the use of Unmanned Aerial Vehicles (UAVs)
equipped with a digital camera.
The paper deals with the acquisition and processing of low-height aerial imagery acquired by UAVs
and Remote Piloted Vehicles (RPVs), in order to provide large-scale mapping to support archaeological
studies: the pros and cons of these acquisition platforms are presented and discussed. These systems
carry out flights that are usually very different from the manned systems as their dimensions and their
light weights never allow the set course to be flown; for this reason, the acquired images are often
affected by large rotations and small overlaps. Therefore, an ad hoc procedure has been implemented to
overcome these limits. In this work, two remote-controlled systems (a mini-helicopter and a mini fixedwing
plane) were tested over two different archaeological sites in order to provide Digital Surface Models
(DSMs) and large-scale maps (numeric maps and orthophotos). Finally, an accuracy evaluation of the
final products is reported.

SR-4000 and CamCube3.0 ToF cameras: tests and comparison

by Dario Piatti

Dario Piatti presentation at RISA 2011

In recent years, a new generation of active cameras, based on the Time-of-Flight (ToF) principle, has been developed.... more In recent years, a new generation of active cameras, based on the Time-of-Flight (ToF) principle, has been developed. The main advantages with respect to other 3D measurement techniques are the possibility to acquire data at video frame rates and to obtain 3D point clouds without scanning and from just one point of view. Several commercial ToF cameras are now available on the market, which presents some differences about sensor resolution, measurement accuracy and maximum distance between camera and object. In particular, the SR-4000 camera by Mesa and the CamCube 3.0 by PMD Technologies have good performances and are well known to researchers dealing with Range Imaging.  Some experimental tests have already been performed on the SR-4000 camera, such as evaluation of the camera “warm-up”, distance accuracy, influence on the distance measurements of the “scattering artifacts” and of the camera orientation with respect to the object surface. The results of similar tests carried out using the CamCube3.0 camera will be reported in this paper, in order to give an idea of the performances of these two ToF cameras.

Il nuovo codice GPS L2C: analisi di qualità del segnale e del posizionamento

by Mattia De Agostino

Co-authored with Ambrogio Manzino, Marco Piras and Chiara Porporato, published in "ASITA 2008 proceedings", L'Aquila (IT), October 21-24 2008, Vol. 1, 969-974, ISBN: 9788890313219.

Italian version:
Il lavoro prende le mosse dall’intenzione di valutare quale sia l’attuale situazione... more Italian version:
Il lavoro prende le mosse dall’intenzione di valutare quale sia l’attuale situazione dell’ammodernamento GPS, ed in particolare del nuovo codice L2C e quali vantaggi si possano ottenere dall’introduzione di quest’ultimo segnale. A tal fine, è stata compiuta un’analisi sui sei satelliti del Blocco IIR-M che ad oggi già trasmettono il nuovo codice civile in aggiunta al codice P2(Y), focalizzando l’attenzione sulla qualità del segnale trasmesso e sulla variazione di precisione nel posizionamento ad una via.

English version:
The paper make an analysis of the status of GPS modernisation, and in particular of the new civil code L2C and of what advantages the introduction of this code could provide. To this purpose, an analysis of the six satellites of Block IIR-M that today already transmit the L2C code in addition to code P2(Y) was carried out, paying particular attention on the quality of transmitted signal and on the variation of one-way position accuracy.

Repertorio delle Stazioni GNSS in Italia. Controllo di qualità e monitoraggio dei dati

by Mattia De Agostino

Co-authored with Ambrogio Manzino and Marco Roggero, published in "SIFET 2007 proceedings", Arezzo (IT), June, 27-29 2007, Vol. 1, 60-67, ISBN: 8890193948

Italian version:
Quante e quali sono le stazioni GNSS permanenti in Italia? E qual è la qualità della... more Italian version:
Quante e quali sono le stazioni GNSS permanenti in Italia? E qual è la qualità della monumentazione, dei dati archiviati e dei metadati? Il presente lavoro cerca di dare una risposta a queste domande, mediante la creazione di un repertorio di quelle stazioni permanenti che rendono pubblici i loro dati, perlomeno alla decimazione a 30 secondi per la post-elaborazione, non affrontando il problema della qualità dei dati trasmessi in tempo reale. I dati archiviati da tali stazioni sono poi stati trattati con il software di calcolo Bernese, allo scopo di individuare le stazioni permanenti che forniscono dati di migliore qualità per scopi statici di elevata precisione, affinando nel contempo la procedura di controllo. L'elaborazione ha prodotto serie temporali significative, per mezzo delle quali è stato possibile valutare la rumorosità dei risultati, che in parte, risulta legata sia alle caratteristiche del sito sia ai reali movimenti della stazione. Un archivio WEB consultabile è stato creato in maniera da rendere disponibile a qualsiasi utenza i risultati ottenuti.

English version:
How many GNSS permanent stations are in Italy, and where they are? Which is the quality of the monumentations, of the stored data and of the metadata? This paper try to make an answer at these questions, by the creation of an inventory of these permanent stations that give public data, with sampling rate at least of 30 seconds for the post-processing, leaving out the quality of data transmitted for the real-time. The stored data from these stations have been processed using the Bernese GNSS software, with the aim of finding the permanent stations that give a good data for high-quality statistics purposes, and also of improving the control procedure. The processing has produced time series for the evaluations of the noise of the results, that, in part, is attached to typology of the site and to effectives movements of the stations. A WEB database where are showed the obtained results.

Uso del segnale L2C nel posizionamento GNSS

by Mattia De Agostino

Co-authored with Ambrogio Manzino, Marco Piras and Chiara Poporato, published in "Bollettino SIFET" issue 1/2009.

L’articolo prende in esame alcuni aspetti della modernizzazione della costellazione GPS, in particolare il nuovo... more L’articolo prende in esame alcuni aspetti della modernizzazione della costellazione GPS, in particolare il nuovo codice civile L2C e i vantaggi derivanti dall’uso. A tal fine si esaminano le misure ricevute dagli otto satelliti che attualmente trasmettono questa misura, assieme al codice P2(Y), con particolare attenzione alla qualità del segnale trasmesso ed all’accuratezza derivante dall’uso del nuovo codice nel posizionamento ad una via. Sono state condotte analisi inerenti i rapporti segnale rumore, i valori di multipath e sono stati ricavati i valori DCB (Differential Code Bias) rispetto al codice P2(Y) e al codice C/A trasmesso sulla prima frequenza. Nel posizionamento ad una via sono stati valutati, con l’uso del filtro di Kalman, i miglioramenti derivanti dall’uso del nuovo codice in relazione ai tempi di fissaggio delle ambiguità, ai rumori residui sulle ambiguità di fase ed ai residui ionosferici.

Applicabilità e attendibilità di sensori GNSS e GNSS/IMU di basso costo per scopi cinematici

by Mattia De Agostino

Co-authored with Alberto Cina, Ambrogio Manzino and Chiara Porporato, published in "Bollettino SIFET" issue 3/2008 (in Italian)

Lo studio condotto valuta quali siano le potenzialità del posizionamento GNSS cinematico e del posizionamento... more Lo studio condotto valuta quali siano le potenzialità del posizionamento GNSS cinematico e del posizionamento integrato GNSS/IMU per scopi di navigazione stradale in termini di precisioni, rendimento e affidabilità impiegando differenti ricevitori e analizzando i risultati sia in tempo reale che in post-processing. Per il tempo reale si analizzano e comparano gli effetti dell' augmentation dovuti ad una rete di stazioni permanenti e all’uso della correzione EGNOS. Le campagne di misura hanno coperto differenti percorsi cinematici in ambiente urbano perché potessero essere abbastanza rappresentative di due città, Vercelli e Torino, nelle quali gli alti edifici e i viali fortemente alberati ostacolano in tutto o in gran parte la ricezione del segnale. Per consentire un confronto immediato dei risultati è stata impiegata una antenna posta sul veicolo connessa con uno splitter a ricevitori singola e doppia frequenza.

Time-of-Flight cameras: tests, calibration and multi-frame registration for automatic 3D object reconstruction

by Dario Piatti

PhD Thesis - April 2011 - Politecnico di Torino (Italy)

1. Introduction
The 3D information of an object to be surveyed can be basically acquired in two ways: using... more 1. Introduction
The 3D information of an object to be surveyed can be basically acquired in two ways: using stereo image acquisitions or optical distance measurement techniques.
The stereo image acquisition is already known and used for decades in the research community. The advantage of stereo vision to other range measuring devices such as LiDAR, acoustic or radar sensors is that it achieves high resolution and simultaneous acquisition of the surveyed area without energy emission or moving parts. Still, the major disadvantages are the correspondence problem, the processing time and the need of adequate illumination conditions and textured surfaces in the case of automatic matching procedures.
Optical distance measurement techniques are usually classified into three main categories: triangulation, interferometry and Time-of-Flight (ToF).
The triangulation normally determines an unknown point within a triangle by means of a known optical basis and the related side angles pointing to the unknown point. This often used principle is partitioned in a wealth of partly different 3D techniques, such as for instance active triangulation with structured illumination and passive triangulation (Jähne et al., 1999).
Interferometry measures depth also by means of the Time-of-Flight. In this case, however, the phase of the optical wave itself is used. This requires coherent mixing and correlation of the wave-front reflected from the object with a reference wave-front. Also in this case, many variants of the optical interferometry principle have been developed, such as multi-wavelength interferometry, holographic interferometry, speckle interferometry and white light interferometry (Jähne et al., 1999). The high accuracies of distance measurements performed with interferometry mainly depend on the coherence length of the light source: interferometry is not suitable for ranges greater than few centimeters since the method is based on the evaluation of very short optical wavelength.
Continuous wave and pulse ToF techniques measure the time of flight of the envelope of a modulated optical signal. These techniques usually apply incoherent optical signals. Typical examples of ToF are the optical rangefinder of total stations or classical LiDAR instruments. In this latter case, actual laser scanners allow to acquire hundreds of thousands of points per second, thanks to fast scanning mechanisms. Their measurement range can vary to a great extent for different instruments; in general it can vary between a tens of meters up to some kilometers, with an accuracy ranging from less than one millimeter to some tens of centimeters respectively. Nevertheless, the main drawbacks of LiDAR instruments are their high costs and dimensions.
In the last few years a new generation of active sensors has been developed, which allows to acquire 3D point clouds without any scanning mechanism and from just one point of view at video frame rates. The working principle is the measurement of the ToF of an emitted signal by the device towards the object to be observed, with the advantage of simultaneously measuring the distance information for each pixel of the camera sensor. Many terms have been used in the literature to indicate these devices, which can be called: Time-of-Flight (ToF) cameras, Range IMaging (RIM) cameras, 3D range imagers, range cameras or a combination of the mentioned terms. In the following the term ToF cameras will be prevalently employed, which is more related to the working principle of this recent technology.
Such a technology is possible because of the miniaturization of the semiconductor technology and the evolvement of the CCD/CMOS processes that can be implemented independently for each pixel. The result is the possibility to acquire distance measurements for each pixel at high speed and with accuracies up to about one centimeter. While ToF cameras based on the phase-shift measurement usually have a working range limited to ten/thirty meters, RIM cameras based on the direct ToF measurement can measure distances up to 1500 m. Moreover, ToF cameras are usually characterized by low resolution (no more than a few thousands of tens of pixels), small dimensions, costs that are an order of magnitude lower with respect to LiDAR instruments and a lower power consumption with respect to classical laser scanners. In contrast to stereo, the depth accuracy is practically independent of textural appearance, but limited to about one centimeter in the best case (actual phase-shift commercial ToF cameras).
The field of real-time ToF camera-based techniques is very active and covers many areas only briefly mentioned in this thesis, which is rather focused on ToF cameras in the Geomatics field.

1.1 Motivation
At present the ability to capture the surrounding area at high speed in three dimensions is one of the most challenging tasks in many fields, such as industrial automation and production, mobile mapping, monitoring, automotive safety, autonomous mobile robotics and gaming.
For both dynamic and static scene there is no low-price off-the-self system that provides full range, high-resolution distance information in real time such as in the case of ToF cameras.
Nevertheless, RIM cameras are usually characterized by some systematic measurement errors, which can strongly worsen the achievable distance measurement accuracy up to tens of centimeters in some cases. Therefore, suitable calibration procedures have to be developed.
One of the main topic of this thesis is to propose systematic procedures for the distance calibration of commercial ToF cameras, in order to estimate and increase their measurement accuracy. The calibration procedure presented in this work belongs to the direct calibration methods, since the distance measurement accuracy of RIM cameras is directly estimated and the resulting systematic errors are modeled. The main idea is to propose a procedure which does not require additional digital cameras or cost-effective high precision measurement racks or robot-arms to calibrate ToF cameras and which can be applied to any kind of RIM camera.
Suitable experimental tests are proposed in order to analyze the influence of several factors on the distance measurements, such as the camera warm-up during working time, the angle of incidence between the camera axis and the object surface, the presence of foreground objects close to the camera and the object reflectivity.
The second main topic of this work is the use of ToF cameras in the Geomatics field, with the final aim of 3D object reconstruction. Since ToF cameras acquire 3D point clouds at video frame rates, this potentiality can surely be exploited for this purpose. The main problem to be faced is the registration of the point clouds acquired from different view-points with ToF cameras. For this purpose, an algorithm for ToF point cloud registration has been developed, which is called multi-frame registration algorithm. Exploiting both the amplitude images and the 3D information delivered by ToF cameras, the proposed algorithm allows to automatically perform the point cloud registration with a final accuracy which is very close to the measurement accuracy of the employed device. Such a result is obtained thanks to frame averaging (so why the term “multi-frame”) and custom-built procedures, also applying an effective filter proposed in this work, which practically removes all “mixed pixels” from the acquired data. Mixed pixels are outliers resulting from the way ToF cameras process multiple returns of the emitted signal: they can strongly affect the accuracy of the acquired point cloud especially in the case of complex scenes. Another challenging topic proposed in this thesis is the integration between ToF data and a multi-image matching approach for automatic 3D object breakline extraction, which can be very useful for speed-up the drawing production of the surveyed objects. In both cases, some improvements are proposed and discussed for future developments.

1.2 Outline
This thesis is organized in six chapters. After this brief introduction, the following chapter faces with the working principle of ToF cameras, dividing them in two categories: devices based on the direct ToF principle and devices which use the indirect ToF principle (phase-shift measurement). Then, the state of the art of this technology is reported, with a complete overview about commercial ToF cameras. A description of the measurement parameters and the typical distance measurement errors of ToF cameras based on the phase-shift measurement (which are the most diffused) is reported, in order to show pros and cons of this new technology.
In Chapter 3, one of the main topics of this thesis is presented, which is the distance measurement calibration of ToF cameras. First, a minimum time (warm-up time) of camera working is established for both the SR-4000 and the PMDCamCube3.0 cameras in order to achieve distance measurement stability. Then, the relation between integration time and distance measurement precision in analyzed for both devices. A distance measurement accuracy evaluation system for the SR-4000 camera is reported, which can be applied for any ToF camera model, and a distance calibration model is proposed which increases the distance measurement accuracy in a wide interval of the whole working range of the camera. Then, a procedure to evaluate the influence on distance measurements of the orientation of the acquired object surface with respect to the camera axis is proposed. The problem of “internal scattering”, which can arise when foreground objects close to the camera are present, is also faced for the SR-4000 camera; finally, some tests on object reflectivity are reported in order to test the performance of ToF cameras on real objects surfaces.
In Chapter 4 a brief summary on the state of the art of applications using ToF cameras is reported, with the aim of showing how this new technology is spreading out in many fields. Then, some applications in the Geomatics field are presented. In particular, a comparison with LiDAR data on real objects and an innovative integration between ToF camera and multi-image matching approach are reported, with some information about future researches.
Chapter 5 faces the ToF point cloud registration problem. First, a brief summary of all main previous works related to ToF point cloud registration is reported, dividing them in two categories: single ToF camera approaches and multiple sensor approaches. Then, the multi-frame registration algorithm proposed in this work is described and some first results about registration of ToF data acquired on both indoor and outdoor scenes are reported. Some results about mixed pixel removal thanks to a suitable filter, which has been implemented and tested in this work, are also reported. Finally, some future works are proposed.
In Chapter 6 conclusions and future developments are discussed. The advantages and problems of the proposed calibration and registration procedures are described in detail.
It is worth nothing that all the algorithms developed in this work have been written in Matlab® code, without any optimization technique since more importance has been given to result reliability than processing speed.

1.3 Abbreviations

A2SIFT Auto-Adaptive Scale Invariant Feature Transform
AGV Automated Guided Vehicle
AMCW Amplitude Modulated Continuous Wave
APD Avalanche PhotoDiode
APS Active Pixel Sensor
AT Acquisition Time
CCD Charge Coupled Device
CDMA Code-Division Multiple Access
CMOS Complementary Metal-Oxide Semiconductor
DSM Digital Surface Model
FDMA Frequency-Division Multiple Access
FOI Field Of Illumination
FOV Field Of View
FPA Focal Plane Array
FPN Fixed Pattern Noise
GC3 Geometrically Constrained Cross Correlation
GCP Ground Control Point
ICP Iterative Closest Point
IMU Inertial Measurement Unit
IT Integration Time
LED Light Emitting Diode
LiDAR Light Detection And Ranging
LMS Least Median Squares
MILSM Multi-Image Least Square Matching
MPF Mixed Pixel Filter
NDT Normal Distribution Transform
NIR Near-Infra-Red
PCA Principal Component Analysis
PMD Photonic Mixer Device
PSF Point Spread Function
RMS Root Mean Square
RIM Range IMaging
RM Relational Matching
ROI Region Of Interest
ROT Read-Out Time
RRL Rescue Robot League
SDMA Space-Division Multiple Access
SFM Structure From Motion
SIFT Scale invariant Feature Transform
SLAM Simultaneous Localization And Mapping
SNR Signal-to-Noise Ratio
SR Swiss Ranger
SURF Speeded Up Robust Features
TDMA Time-Division Multiple Access
ToF Time-of-Flight
TrICP Trimmed Iterative Closest Point
TS Total Station
WDMA Wavelength-Division Multiple Access

Past naturally-induced changes on the development of a man-made landscape: the historical environment of Castignano and Offida (central Italy)

by Alessio Cinti

with Prof. L. Coppola, Department of Geological Sciences, University of Basilicata, Potenza, Italy

GIMPhI: A novel vision-based navigation approach for low cost MMS

by Mattia De Agostino

Co-authored with Andrea Lingua, Francesco Nex and Marco Piras, published in 'Position Location and Navigation Symposium (PLANS), 2010 IEEE/ION', 2010

Over the last two years, the Geomatics research group at the Politecnico di Torino has developed a Low Cost System, in... more Over the last two years, the Geomatics research group at the Politecnico di Torino has developed a Low Cost System, in which only low cost sensors are involved. The system is equipped with webcams, an MEMS IMU and up to four GNSS receivers. During this development, several (non negligible) problems have been solved in order to obtain good quality after the data processing. One of the main problems of the low cost systems concerns the occurrence of GNSS outages. In this case, the IMU can only estimate the trajectory and the attitude of the vehicle for short periods. For this reason, considering the high number of frames available (about 3–5 frame per second, fps), a vision-based navigation (VBN) approach, called GIMPhI (GNSS IMU and PHotogrammetry Integration), has been adopted and tested. The navigation solutions have been refined by means of integration with a photogrammetric approach (bundle block adjustment) and a rigorous weight matrix has been adopted in order to consider the different accuracies of the various sensor observations (GNSS, IMU and images). A detailed description of this integrated approach is presented in this paper. The first tests and the achieved results are then shown in order to evaluate the reliability of the proposed approach.

Performances comparison of different MEMS-based IMUs

by Mattia De Agostino

Co-authored with Ambrogio Manzino and Marco Piras, published in 'Position Location and Navigation Symposium (PLANS), 2010 IEEE/ION', 2010.

MEMS inertial sensors are widely used for navigation applications where size, weight, power and cost are key sides,... more MEMS inertial sensors are widely used for navigation applications where size, weight, power and cost are key sides, such as autonomous vehicular control and pedestrian navigation. Otherwise, if there is no doubt that MEMS technologies represents an interesting turning point for low cost inertial-based sensors and applications, nevertheless it is absolutely true that, in order to obtain good positioning accuracies, it is necessary to investigate very well the behaviour of these MEMS sensors and realize special test calibrations, both in static and kinematic conditions. In order to evaluate the potentialities (and the limits) of these sensors, comparative tests have been realized considering MEMS inertial sensors with different characteristics and different performances, First of all, a static calibration of the sensors has been made, in order to compare the bias values and their stability with respect to the time. In particular, an Allan-variance analysis and a modified six position static test were carried out for each sensor, preserving carefully the same environment conditions for all the tests. After the lab tests, the performances of all the sensors were compared in a field kinematic test, integrating their data with a GPS solution.