Potential and limitation of UAV for monitoring subsidence in municipal landfills Article PDF Available in International Journal of Environmental Technology and Management 1711 13 January 2014 with 1064 Reads DOI 101504IJETM2014059456 Cite this publication Daniela Gasperini Pascal Allemand 368 Claude Bernard University Lyon 1 Christophe Delacourt 3409 Université de Bretagne Occidentale Philippe Grandjean 1752 Claude Bernard University Lyon 1 Abstract Multitemporal topographic measurements are essential for monitoring municipal landfills for economic and security reasons Accurate evaluation of the landfill volumes still to exploit and the extent of subsidence occurring in the closed plots are critical parameters in landfill management A municipal landfill located in central Italy has been imaged by a UAV helicopter able to fly in full autonomy in industrial areas Very high resolution images have been processed by a photogrammetric chain in order to obtain Digital Surface Models and orthorectified images The resolution of these products was 28 cm and the vertical precision of the DSM was at Discover the worlds research 15 million members 118 million publications 700k research projects Figures uploaded by Pascal Allemand Author content General maps and images of the study area a Position of the landfill in Italy b Aerial view of the landfill The studied plot is elongated in the North South direction in the centre of the landfill c Orthoimage of Plot no 3 with contour linesequidistance of 2 m The red boxes show the position of the images of Figures 3 and 5 d DSM of Plot no 3 with contour linesequidistance of 2 m see online version for colours DRELIO system The ground control system comprises a computer on which are connected an antenna for the communication a joystick and a joypad for driving the helicopter in fully manual or assisted manual modes The helicopter is 2 m long It is equipped with a GPS a magnetometer and a pressure sensor not visible on the image The autopilot can assist the pilot in manual mode or can drive the helicopter in full automatic mode see online version for colours a Detail on a yellow 10 cm diameter target used for the calculation of the external parameters of the camera b Detail of the orthoimage at the junction between two images The limit is visible in term of photometry The image of the pipes is not affected by the limit of the two images c and d Orthoimage of the drainage ditch which bounds the top of Plot no 3 and the corresponding DSM and section The 04 m deep drainage ditch is visible on the topographic section Content uploaded by Pascal Allemand Author content Download fulltext PDF Int J Environmental Technology and Management Vol 17 No 1 2014 1 Copyright 2014 Inderscience Enterprises Ltd Potential and limitation of UAV for monitoring subsidence in municipal landfills Daniela Gasperini Dipartimento di Scienze della Terra Università di Pisa via S Maria 53 56126 Pisa Italy Email gasperinidanielagmailcom Corresponding author Pascal Allemand Laboratoire de Géologie de Lyon Université Lyon 1 ENSLyon CNRS UMR 5276 LGLTPE 2 rue Raphaël Dubois 69622 Villeurbanne Cedex France Email pascalallemandunivlyon1fr Christophe Delacourt Laboratoire Domaines Océaniques Université de Brest UMR6538 IUEM Place Nicolas Copernic 29280 Plouzané France Email christophedelacourtunivbrestfr Philippe Grandjean Laboratoire de Géologie de Lyon Université Lyon 1 ENSLyon CNRS UMR 5276 LGLTPE 2 rue Raphaël Dubois 69622 Villeurbanne Cedex France Email philippegrandjeanunivlyon1fr Abstract Multitemporal topographic measurements are essential for monitoring municipal landfills for economic and security reasons Accurate evaluation of the landfill volumes still to exploit and the extent of subsidence occurring in the closed plots are critical parameters in landfill management A municipal landfill located in central It aly has been imaged by a UAV helicopter able to fly in full autonomy in industrial areas Very high resolution images have been processed by a photogrammetr ic chain in order to obtain Digital Surface Models and orthorectified images The resolution of these products was 28 cm and the vertical precision of the DSM was at worse 05 m resulting into acceptable errors better than 5 on available volume est imations The DSM has been compared to elevation values produced by conventional theodolite and LIDAR measurements It is shown that the UAV helicopter system is more flexible and more produc tive than the two other techniques for a similar precision 2 D Gasperini et al Keywords municipal landfill subsidence unmanned aerial vehicle photogrammetry European Directive Reference to this paper should be made as follows Gasperini D Allemand P Delacourt C and Grandjean P 2014 Potential and limitation of UAV for monitoring subsidence in municipal landfills Int J Environmental Technology and Management Vol 17 No 1 pp113 Biographical notes Daniela Gasperini is a Earth Scientist with a strong background in Isotope Geochemistry She developed innovative protocols for radiogenic isotopes and isotope compositi ons of stable elements for studying small to largescale processes to cons train mantle sources and dynamics In parallel she has participated in vari ous European projects dealing with Environmental Sciences She studied potential and limitation of Thermal Infrared Images to prospect the state of rivers She is at the origin of the idea of landfill monitoring from drone images Pascal Allemand is a Geomorphologist He has been working on transfer of sediments at the surface of Earth and Mars For that he used DEM computed from images acquired by satellites pl anes or UAV Now he works on the relationships between clima tic change and erosion in the tropical belt and on Mars He developed the processing chain used for computing DEM from DRELIO images Christophe Delacourt is a Physicist expe rt in Remote Sensing He developed various techniques based on radar and op tical images to derive the velocity field of landslides in mountainous areas Then he worked on the coastal fringe and used remote sensing da ta to study sedimentary transfer from continental watersheds to deep marine domain For that he promoted the use of various underwater high resolution bathymetric se nsors He is at the origin of the DRELIO system Philippe Grandjean is an Engineer expert in mechanics and electron ics He built entirely the DRELIO system Moreover he improved the technique of civil UAV piloting and got the pilot certificate He imagined and built new systems on board of UAV planes and helicopters able to acquire hyperspectral data He belongs to the group of experts who define the French UAV regulations 1 Introduction European Landfill Directive CD 199931EC and related national implementing measures in the EU countries ensure that landfills are built in suitable geological areas and carefullyengineered to protect the envi ronment from eventual contaminants which may be present in the solid waste stream Federal regulations also obliges continuous monitoring systems to guarantee that landfill bottom line leachate co llection cover and natural geological setting preserve their orig inal features in time Subs idence that can occurs during and after the landfill activity is a major indicator of the quality of the system in both environmenta l and economic terms Twice a year a detailed monitoring of la ndfill subsidence surfaces is essential to maintain productive and safe operations and avoid ongoing risks such as structural collapses Actually landfills including a si gnificant fraction of degradable litter are characterised by a steady generation and accum ulation of gases throughout the refuse Potential and limitation of UAV 3 landfill material eventually tapped by reclaiming apparatus such as gas piping inserted deeply into the filled areas Propagation toward surface of voids or cavities in the fill due to primary consolidation and secondary c ompression of the waste mass corrosion oxidation or biochemical decay of waste materials and undergroun d gas emissions can severely damage the cover generating ten sion cracks in soils and ground subside nce Moreover the occurrence of sinkholetype depr essions in the fill increases potential for exposures and causes damage to any built environment such as foundations and gas pipes Otherwise efficient compacting waste into the smallest practical volume ensures new room for piling material by controlled subsidence and longer landfill life thus guarantying both profits in the landfill economy and advantage for the environment Ground subsidence in well managed landfill is a slow process that does not exceed 5 of the total thickness of accumulated waste Spikula 1997 Before their occurrence sinkholes depressions and collapses have surface expression that can be as small 1 m 2 or less Kuo et al 2005 The detection of areas in subsidence as soon as possible is a strong challenge of landfill monitoring Ground subsidence monitoring has bee n successfully performed on undergr ound coal mines and urban sites main ly by using geodetic met hods eg levelling and GPS surveys LIDAR Laser Imaging Detection and Ranging borehole extensom eters high resolution magnetic survey multichannel elect rical resistivity microgravity profiling and Differential SAR Interferom etry Synthetic Aperture Radar techniques eg Carnec and Delacourt 2000 Abidin et al 2004 HayMan et al 2009 Leick 2003 Xia and Miller 2007 Zhang et al 2011 Equipped la ndfill lines eg highdensity polyethylene geomembranes with attached c ontinuous optical fi bers were also proposed as strain sensors to monitor landfill subsiden ce Borns 1997 Spikula 1997 Accuracy of groundb ased measurements of vertical displacements by Terrestrial Laser Scanners TLS tacheometers or DGPS ranges from several centimetres to 1 cm Galloway et al 2000 Delacourt et al 2007 These techniques can not attain a sufficiently high spatial density over large areas and are time consuming Conversely under ideal conditions differential SAR Interferometry DInSAR and DGPS can achieve similar accuracy to monitor even larg e phase gradient deformations suc h those induced by volcanic activity and earthquake phenomena Lu et al 2005 2007 Advanced InSAR techniques e g IPTA Interferometric Point Target Analysis Werner et al 2003 PS Permanent Scatterers InSAR Ferretti et al 1999 2001 have been widely used to map longlasting a nd slowevolving deformati ons such as ground subsidence Mora et al 2003 These spatial me thods are accurate but need to be applied on surfaces larger than landfill areas Neverthe less classical remote sensing methods by images requiring highresolution satelliteaer ial data or dedicated LIDAR missions may be too expensive within the business management of municipal landfills By contrast UAV Unmanned Aerial Vehicles helicopters are less expensive and their size is considerably smaller than any other conventional aerial technology allowing high resolution aerial imagery at low altitude ev en if accomplished thro ughout narrow paths Image acquisition by the UAV helicopter can be preci sely scheduled and set up in a few hours and the utilisation of its equipment is not covered by civil aeronautics regulation which offers advantages in terms of flexibility The aim of this paper is to evaluate the potential and limitation of a chain of acquisition and processing by photogrammetry of images acquired by a UAV helicopter in order to monitor slowevolving proces ses such as waste compactness and landfill subsidence recognised as a major threat in causing eco nomic loss to management of rubbish damps A campaign of im age acquisition by an autonomous UA V helicopter 4 D Gasperini et al called DRELIO Delacourt et al 2009 has been realised in June 2009 on a landfill located in Tuscany The Digi tal Surface Model DSM and the associated orthoimage of a plot have been computed from the images The precision of the DS M is discussed relative to GPS measurements and to data acquired by conventional theodolite technique few months before the image acquisition 2 Description of the site The study landfill is named Scapigliato controlled by REA Rosignano Energia Ambiente for the local municipality of Rosignano Marittimo Tuscany central Italy Figure 1 and at present it consists of four plots The Scapigliato lan dfill covers an area of about 800 600 m 2 that is placed within 150 m thick lowpermeability layers consisting of Lower Pleistocen e blue clays characterised by the absence of aquifers According to the current European and Ita lian regulations it is classified as non hazardous waste landfill and is equipped of a modern system of biogas piping and recycling The damp cultivation takes into account the mechanical and chemical characteristics of the waste and proceeds by subsequent filling of different portion s plots Once the cultivated plot reaches the planned final size it is completely sealed with a coating of clay that insulates the mass of waste preventing exposure and the infiltration o f rainwater The environmental reclaiming is fi nally achieve d by an appropriate planting This procedure ensures that one plot of the st udy area is relatively stable and can be used as reference for the technique discusse d in this paper Figure 1 General maps and im ages of the study area a Position of the landfill in Italy b Aerial view of the landfill The studied plot is elongated in the North South direction in the centre of the landfill c Orthoimage of Plot no 3 with contour lines equ idistance of 2 m The red boxes show the position of the images of Figures 3 and 5 d DSM of Plot no 3 with contour lines equidistan ce of 2 m see online version for colours Potential and limitation of UAV 5 3 Data acquisition and processing Although platforms such as kites microlig hts and UAV have been tested for surveying landslides Casson et al 2005 for mapping Alpine rivers Lejot et al 2007 as well as for agricultural eg Sugiura et al 2005 and coastal applications Delacourt et al 2009 none of them have ever been used to moni tor domestic waste dump Our system was developed to overcome the const raints sp ecifically associated to industrial conditions namely flight in waste dump or indust rial sites small takeoff and landing are as and complex topographic conditions related to building Furthermore products derived in this study as multitemporal DSM and orthophotogra phy have not been calculated elsewhere 31 Drelio helicopter The DRELIO DRone hELIcoptère pour lO b servation de lenvironnement system consists of four main parts Figure 2 a the helicopter b the payload for scientific sensors c the onboard flight control system FCS and d t he ground control station GCS for mission planning and c ontrol The helicopter is a Vario rigi dified acrobatic model equipped with a 26 cm 3 thermic engine R otation speed of blades has been reduce d to 1300 lapsminute in order to limit vibrations and to increase flight stability Despite this limitation the maximum speed reaches 70 kmh 1 The ma ximum duration of a flight is 45 minutes The total empty wei ght is 11 kg with a maximum payload of 4 kg Figure 2 DRELIO system The ground control system comprises a computer on which are connected an antenna for the communication a joystick and a joypad for driving the helicopter in fully manual or assisted manual modes The he licopter is 2 m long It is equipped with a GPS a magnetometer and a pr essure sensor not visible on the image The autopilot can assist the pilot in manual mode or can drive the helicopter in full automatic mode see onlin e version for colours 6 D Gasperini et al The ground control station is connecte d to the on board flight control sy stem The GCS pilots the acquisition instrume nts in terms of time of start and fr equency of the acquisitions A programmable autopilot connected to an atmospheric pressure sensor an inertial sensor a geomagnetic direction se nsor and a GPS drives and stabilises the helicopter DRELIO is thus able of fully au tomatic takeoff hovering flight plan following and landing Its integrated radi o link allows data communication up to 60 k m Depending on the mode of t he autopilot manual hove ring or planned flight manual joystick or semimanual joypad rem ote controls can be used Whatever the mode of the autopilot all the orders both automatic and manual are collected and transmitted through a software The payload consists classically of a profe ssional reflex camera installed under the helicopter The camera is a Nikon D2 00 with a 35 mm Nikkor l ens The size of sensor is 236 158 m m which gives an equivalent focal length of approximatel y 52 mm As the control station is linked to a GPS series of specific photo graphs can be programmed in order to realise multitemporal comparisons from the same point and angle of view A video camera installed on the view finder of th e reflex camera tra nsfers in real time to the ground the images visible through the reflex camera This low resolution video is used to control the swath coverage during the acqui sition only To optimise the missi ons and reduce the number of images necessary to c over a given zone lenses with a focal length smaller than or equal to 50 mm are used Pi xel size ranges from 1 cm to 4 cm with a focus length of 50 mm and a flight altitude classically ranging from 50 m to 200 m In that case the swath ranges from 50 m to 200 m The missions are planned early in the mornin g or late in the evening at rising sunlight when the studied industrial site is not i n activity The light is homogeneous and the lack of shadows allows a good processing of im ages Moreover the period of dawn and twilight are characterised by low wind thus ensuring a good stability If several missions are planned over the same area they will be realised in the same solar illumination conditions The flight plan of DRELIO is first loaded in the autop ilot from the ground station The flight plan is made up of the position of points where DRELIO has to change its course the velocity betw een two points the DRELIO landing location and the emergency landing site in case of link breakoff between the station and the helicopter Before takeoff DRELIO is veri fied according to a check list B oth mechanical electronic and image systems are checked Th en the engine is started up After the heating of the engine t he mission is launched by a start u p order given to the software Continually the fli ght can be controlled from a m anned remote control if a problem is detected After the flight the images are transferred from the camera to a computer in order to be inspected If the quality of the images is su fficient the mission is over 32 DSM and orthoimages processing Digital Surface Models DSMs can be derived using photogramm etric techniques applied on at least two images called a stereosc opic pair or set that are acqui red over the same area from different view angles andor di fferent positions This technique requir es knowledge of the optical characteristics of the camera and the position and orientation of the camera at the time of acq uisition which are called external parameters The optical characteristics of the camera are calibrated be fore the mission Ka sser and Egels 2002 The external parameters of the camera are defined for each image Potential and limitation of UAV 7 The calculation of a DSM from stereoscopic images acquired by DR ELIO is based on methods similar to those used to derive DSM from classical airborne missions However some specificities of DRELIO acquisition produce some additional constraints The first problem is to control and obtain a precise set of external parameters In terms of altitude and orientation the flight of DRELIO is not as stable as that of a plane Moreover GPS equipment on board of DRELIO does not give sufficiently accurate results regarding the spatial resolution of the images The external parameters of each image are thus poorly defined The precision on these paramete rs is increased using Ground Control Poi nts GCP identified by yellow targets installed on the ground before acquisitions and geolocated by GPS with a precision of 50 cm Figure 3a Using the absolute locations of these points and their positions on th e images minimisation methods have been developed to increase the accuracy of the external parameters Kasser and Egels 2002 In the following step the position of eac h poin t on the first image is associated with the position of the analogous point in the second image The correspondence between the pixels of the two images is calculated by maximising a correlation functi on Casson et al 2005 Delacourt et al 2004 Baratoux et al 2001 that is used to measure the shift between each point of the two im ages At last the photogramm etric equations are applied to each pair of correlat ed points to determine their 3D coordinates Kraus and Waldhaüsl 1994 Orthophotographies im ages corrected from geometrical and to pographical distortions are then computed from the DSM and one of the images of the stereoscopic pair The individual DSMs and orthoim ages can be easily mosaicked as they are in the reference frame given by the GPS gro und control points Figure 3 a Detail on a yellow 10 cm diameter target used for the calculation of the external parameters of the camera b Detail of the orthoimage a t the junction between two images The limit is visible in term of photometry The image of the pipes is not affected by the limit of the two images c and d Orthoimage of the drainage ditch which bounds the top of Plot no 3 and th e corresponding DSM and section The 04 m deep drainage ditch is visibl e on the topographic section 8 D Gasperini et al The acquisition has been achieved on Plot no 3 of the landfill Figure 1 This plot is a North South elongated hill with a flat top It has an approximate length of 300 m for a width of 50 m and a height of 25 m above the neighb ouring areas The plot has been cultivated from 2004 to 2006 and thus closed since 3 years at the time of the experiment It is covered by a clay layer on which some shrubs and grass grow The eastern side of the plot located on the active side of the landfill has been covered by a second layer of clay few months before the collection of the images by DRELIO and subsequent ly a campaign of measurements by theodolite was carried out to control the subs idence evolution The image campaign acquisition was perform ed in June 2009 Ten targets used to localise the images were placed on the top and on the sides of Plot no 3 Three targets were placed on the parking area located south of the plot The cartogra phic positions of the targets were measured in the Gauss Boaga Roma 1 projection using a Leica GS50 singlefrequency GPS used in static mode The precision of the measurements was around 05 m after a post treatment The fli ght of DRELIO lasted 30 minutes at an elevation of around 150 m above the ground DRELIO acquired a complete cover of the plots 1 2 and 3 Twenty five colour images of the Plot no 3 were used to derive the DSM and the orthoimages 4 Results Twenty five images were used to compute the DSM and the orthoimage of Pl ot no 3 georeferenced in the GaussBoaga Roma 1 system at a resolution of 28 cm The text ure level of the images acquired by DRELIO is high Thus objects as small as 3 pixels can be observed and correlated These objects are sm all pebbles or topographic irregularities More than 95 of the pixels are correlated giving welldefined products The DSM and the orthoimage are integrated into a geographic inform ation system GIS comprising also an elevation map derived from theodolite measurements and used to manage the landfill The details of the topography such as those of the pipes used to collect the bio gas are visible on the DSM Structures such as the ditch bounding the flat top area of the plot are also visible in the DSM Figure 3c and d The boun daries of the individual images are visible on the global orthoimage because they have not the same radiometry However the continuity of the elements such as the pipes is not affected when they crosscut the limits of two images Figure 3b Figure 4 shows the relation between the elevations of the GPS points used to produce the external orientation of the images and the elevation of these points on the resu lting DSM The correlation coefficient between th e two datasets is 092 The maximum of difference between the DSM and the GPS value is around 05 m which is the error value on the GPS measurements A comparison can be al so done at the first order with the map used to administrate the landfill The contour lines of the DSM produced by photogrammetry and the contour lines visi ble on the map are parallel and very simil ar in elevation The difference in el evation of the DSM relative to 2 reference points located on the top of Plot no 3 is less than 20 cm Finally the part of the DSM located on a smal l parking at the south of Plot no 3 display s less than 20 cm of difference with the elevati on proposed by the map Potential and limitation of UAV 9 Figure 4 DSM elevation vs GPS elevation measured at the posit ion of the target red square and DSM elevations vs reference point elevations black stars The correlation between the two data sets is 092 see online version for colours Figure 5 a Detail of the slope located at the transition with the active plot on which the difference between the elevation measuremen ts made by theodolite and the DSM are reported The difference displays a clear bulge pattern b DSM elevat ion vs theodolite measurements see online version for colours a b 10 D Gasperini et al The DSM of the slope located at the South Ea st of the plot at the transition with the active landfill can be compared with the meas ures obtained by a theodolite four month s before our experiment Figure 5 The elev ation of the slope has been measured with a point density of 10 pointsm 2 These points have been int egrated in the GIS The difference in elevation between the photogrammetric DSM and the theodolite measurements show bulge geometry The elev ation values of the DSM in the centre of the slope are 06 m to 1 m high er than those collected by the theodolite The differences between the DSM and the theodolite measurements are close to 0 on the top of the slope and are negative on a narrow band at t he base of the slope Figure 5 5 Discussion This work raises questions about the value of the method for landfill management The parameters related to topography that have to be checked for landfill management are 1 the volume of a given plot that rem ains available for dumping 2 the evoluti on of topography related to the accumulat ion of waste in an active plot or 3 the evolut ion of subsidence of a plot after its closure The econ omic question is also important for selecting these techniques with resp ect to the ones classically used 51 Precision of the DSM The precision of the DSM is similar to the p recision of the ground control points used t o estimate the external parameters of the came ra that is 05 m The elevations of three points measured by the theodolite on the top of the plot are also similar to the elevation of the same points measured on the DSM within an interval of less than 020 m The average height of Plot no 3 is of 25 m above the path that bounds the plot west ward If one considers this height as the thickness of the plot an absolute error of height rang ing from 02 m to 05 m represents a relative error between 08 and 2 The slope located on the eastern side of Plot no 3 displa ys a bulge relative to the elevation values measured by the theodolite This bulge is 20 m long and 04 m high in its centre According to the sta ff of the landfill this part of the slope has been reinforced by a clay layer after the theodolite measurement and before the DRELIO experiment The bulge is thus a topographic feature that has been hi ghlighted by the photogrammetric DSM DRELIO data and the photog rammetric chain allow detecting variati ons in DSM in the range of the precision of the DSM if the surface concerne d by elevation variation is large enough The accuracy of the single frequency GPS data use d in this work was around 050 m after postprocessing With a DGPS t he precis ion of the measurement of the target can easily reach 005 m That would lead a precision similar for the DSM Differential DSM s Kasser and Egels 2002 Kraus and Wald haüs l 1994 which are used to estimate the subsidence would be produced with a pre cision of 01 m which is sufficie nt to monitor the subsidence of landfill and to prevent damages that can occur in relation to the subsidence Potential and limitation of UAV 11 52 Cost and efficiency of the Drelio chain relative to other methods The DSM produced by DRELIO is at a resolution of 28 cm More than 90 of the points of the DSM results from the photog rammetric computation The other poi nts have been estimated by interpolation The point density is thus above 1000 ptm 2 that is more than 200 times the point density produced by theodolite measurement An experiment with DRELIO on the entire landfill lasts less than 4 hours taking into account the positioning and measure of 100 targets The photogrammetric computatio n takes 4 hours of data management and 20 hours of calculation A DSM of the complete landfill can be produced in less than 3 days wi th point density of 1000 ptm 2 This technique is thus more efficient than classical theodolite me thods Moreover such DSM can be produce d by LIDAR techniques A Terrestrial Laser Scan can m easure topography with very high accuracy and high resolution However th is method also requires the positioning of ground control points The point densi ty decreases also with the distance of the instrument The point density is of 100 0 ptm 2 at 5 m from the instrument and decreases to 5 ptsm 2 at 80 m from the instrument So a DSM constructed at least with 100 ptm 2 requires at least 10 stations of measurement in the studied landfill LIDAR data have to be cleaned of defect before their interpolation t o give a DSM This process is manually achieved done by the hand and requires at least t wo days on his example for an expert Moreover the LIDAR is a very expensive instr ument DRELIO and photogramm etry are thus the most productive tools as they generate high density DSM at the lowest cost 6 Conclusions The DRELIO system proves itself as very efficient in order to monitor municipal landfills A DRELIO campaign can be conducted before the opening of the landfill or after its closure In less than one hour a surface of 1 km 2 can be imaged at very high resolution better than 3 cm The images can be used to compute digital elevation models and orthoimages which can be integrated in GIS These products are efficient to measure volumes already used or volumes that remain to be filled Moreover the precisions of the data are sufficient to follow the possible su bsidence of closed plot s Compared to theodolite DRELIO system is much more productive as it is faster and produces up to 100 times denser clouds of points Compared to LID AR DRELIO system is less expensive faster and simpler to implement for a similar results in terms of density of points Moreover DRELIO system produces an orthoimage that is not pr ovided by the other methods The experiment has been carried out using a single freque ncy GPS with a poor accuracy The precision of the DSM is similar to the precision of the GPS data The use of a DGPS will strongly impr ove the accuracy of the results Acknowledgements The Director M Monti V Lami S Ricci L Cianchi and the personal of the landfill and the Municipality of Rosignano Marittimo Livorno are warmly acknowledged for their interest in this work and for the time spent on this project 12 D Gasperini et al References Abidin HZ Andreas H Gamal M Hendrasto M and Suganda OK 2004 The use of GPS surveys method for natural hazard mitigation 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methodology can be greatly improved and made much more efficient through the use of UAVs Unmanned Aerial Vehicle aerial photogrammetry and model overlapping analysis Comparing to ground based methods and any other conventional aerial technology UAVs are costefficient and smaller providing a highresolution aerial image at low altitude 37 Photogrammetric Techniques for Monitoring Vegetation and Topographical Changes Conference Paper Jul 2018 Lukas Moravits Alexandra Sokolova Micah Murdock Mahdi Safa Lechner et al 2012 used a UAV to study subsidence resulting from underground coal mining that can alter the structure of overlying rock formations Gasperini et al 2014 analysed the UAV potential for monitoring displacement in landfill areas in particular the evolution of subsidence after the closure producing a digital surface model DSM with a precision of 01 m This level of quality is sufficient to monitor the subsidence by the differential DSM technique Gasperini et al 2014 Gasperini et al 2014 analysed the UAV potential for monitoring displacement in landfill areas in particular the evolution of subsidence after the closure producing a digital surface model DSM with a precision of 01 m This level of quality is sufficient to monitor the subsidence by the differential DSM technique Gasperini et al 2014 The application in coastal environments for subsidence analysis is still poor due to the high level of error and the consequent high quality of measurements and ancillary data required Coastal Subsidence Causes Mapping and Monitoring Chapter Mar 2018 Loreta Cornacchia Ciro Manzo Emiliana Valentini Andrea Taramelli Therefore use of modern remote sensing techniques to support conventional geotechnical measurements in the impoundmentscale monitoring of tailings could improve the management of tailings and extend existing knowledge of tailings behavior Unmanned aerial vehicles UAVs can enable costand workefficient surveillance of waste facilities 131415 16 UAVs and Structure from Motion SfM photogrammetrya lowcost topographical survey technique developed from computer vision and conventional photogrammetry techniqueshave gained popularity as a fast and flexible data acquisition system that can be used to produce orthomosaics and 3D models 131415 UAV Remote Sensing Surveillance of a Mine Tailings Impoundment in SubArctic Conditions Article Dec 2017 Anne Tuomela Corine Davids Anssi Rauhala Pekka M Rossi GEODESY CARTOGRAPHY AND AERIAL PHOTOGRAPHY Article Sep 2016 V I Nikulishyn EO SHylo КR Tretyak V А Lozynskyi Modern Technologies of Geomatics Applied to Engineering Geology Article Dec 2016 Riccardo Salvini The integration of satelliteairborne sensing with ground based spectral and chemical measure ments is proving of interest for the detection and monitoring of waste disposal areas Manzo et al 2016 Alexakis et al 2016 Recently the development of unmanned aerial vehicles UAV and unmanned ground vehicles UGV capable of carrying spectral and chemical sensors Persechino et al 2010 Gasperini et al 2014 Roldán et al 2015 has improved the in situ analysis to determine ground truths and improve field surveys Such upcoming technologies provide numerous opportunities for novel applications both of optical and thermal analyses Lega et al 2014a b adopted a thermal pattern and tracking approach integrating drone platforms and advanced sensors in order to identify superficial anomalies over landfill areas and possible polluted sites Gasperini et al 2014 analysed the digital surface model derived using photogrammetric techniques for subsidence monitoring in municipal solid waste dumps Persechino et al 2013 and Manzo et al 2016 investigated the definition of a hierarchical protocol to monitor landfill areas by integrating different tools in topdown approaches However by using the pole photogrammetry support good results were obtained for the 3d extraction Moreover the 3d models by Structure from Motion SFM Lowe 2004 is a promising tool for monitoring subsidence in municipal solid waste landfills its morphology and temporal superficial variation Gasperini et al 2014 and for defining an accurate elevation model as input for emission simulation by local atmospheric modelling Manzo 2012 Unfortunately we performed only one data in situ survey utilising the pole as it required significant work for the collection and postprocessing steps to obtain a 3d model accurate enough for inspection and comparison with thermography of the accessible areas of the target site Topdown approach from satellite to terrestrial rover application for environmental monitoring of landfills Article Jan 2017 SCI TOTAL ENVIRON Manetti Piero Alessandro Mei Ciro Manzo Emiliano Zampetti Development of an intelligent least squares based linear controller for autonomous helicopters Conference Paper Jun 2016 Ilkay Yavrucuk Eser Kubali Ad

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