Application of Unmanned Aerial Vehicle for Landslide Mapping

Transcription

1 TS 6 New Technologies in Engineering Geodesy and Multisensor Systems Application of Unmanned Aerial Vehicle for Landslide Mapping Marijan Car 1, Danijela Jurić Kaćunić 1, Meho-Saša Kovačević 1 1 Faculty of Civil Engineering, University of Zagreb, Kačićeva 26, Zagreb, Croatia, mcar@grad.hr, djk@grad.hr, msk@grad.hr Abstract. Landslides are a worldwide phenomenon that can have a strong economic impact on the infrastructure objects and sometimes tragically result in fatalities. There are many factors that can make an area prone to a landslide, like drainage and removal of vegetation that can be controlled, as well as some other factors such as topography and slope material that is difficult to control. Accessing and mapping such locations can be dangerous and unapproachable. Unmanned Aerial Vehicle (UAV), commonly known as drone is a remotely piloted aircraft that can be used to collect series of high resolution images from which it is possible to create Digital Terrain Model (DTM) of a landslide. By using such models, it is possible to generate volumes, areas, cross sections and contour lines in a very short time. This paper gives an overview of a modern remote sensing method using Unmanned Aerial Vehicle DJI Phantom 2 Vison+ and Pix4Dmapper software on a landslide which occurred on the rail notch Doljan in km , railway track R201 Zaprešić Čakovec between railway stations Novi Marof Turčin. Keywords: Digital Terrain Model, andslide, Phantom 2 Vison+, Pix4Dmapper, Unmanned Aerial Vehicle. 1. Introduction A landslide is defined as "the movement of a mass of rock, debris, or earth down a slope" [Cruden 1991]. Landslides are a type of "mass wasting" that denotes any down-slope movement of soil and rock under the direct influence of gravity. The term "landslide" encompasses five modes of slope movement: falls, topples, slides, spreads, and flows [Figure 1.1]. These are further subdivided by the type of geologic material (bedrock, debris, or earth). Almost every landslide has multiple causes. A slope movement occurs when forces acting down-slope (mainly due to gravity) exceed the strength of the earth materials that compose the slope. Causes include factors that increase the effects of down-slope forces and factors that contribute to low or reduced strength. Landslides can be initiated in slopes already on the verge of movement by rainfall, snowmelt, changes in water level, stream erosion, changes in ground water, earthquakes, volcanic activity, disturbance by human activities, or any combination of these factors. Earthquake shaking and other factors can also 549

2 SIG 2016 International Symposium on Engineering Geodesy, May 2016, Varaždin, Croatia induce landslides underwater. These landslides are called submarine landslides and sometimes cause tsunamis that damage coastal areas. Landslides can move slowly, (millimeters per year) or can move quickly and disastrously, as is the case with debris flows. Debris flows can travel down a hillside at speeds up to 320 kilometers per hour (more commonly, kilometers per hour), depending on the slope angle, water content, volume of debris, and on type of earth and debris in the flow. These flows are initiated by heavy, usually sustained periods of rainfall, but sometimes can happen as a result of short bursts of concentrated rainfall or other factors in susceptible areas. Burned areas charred by wildfires are particularly susceptible to debris flows, given certain soil characteristics and slope conditions [URL 1]. 550 Figure 1.1 Types of landslides: (1) fall, (2) topple,(3) a slide,(4) a spread, (5) a flow 1.1. Landslides in Croatia General geological conditions in Croatia are complex. There are three main macro regions that can be distinguished from the aspect of engineering geological

3 TS 6 New Technologies in Engineering Geodesy and Multisensor Systems conditions and mass movements: (I) the Pannonian depression where mass movements occur in soils, (II) the Karst area where mass movements occur in rocks (rock falls) and (III) Adriatic coast and islands where mass movements occur in soils and rocks. [Jurak et al. 1996]. Typical landslide models for each region are shown in [Figure 1.2]. According to the available data most of the landslides occur in soils and clayey materials of macro region I1 I3. The karst area of macro region II covers the mountainous area of Croatia where carbonate rocks are dominant with rock falls. Flysch is typical for macro region III1 and III2 in which badlands can be formed (especially in III2). Figure 1.2 Division of Croatia into macro regions by typical model of mass movement: (I) the Pannonian depression, (II) the Karst area and (III) the Adriatic coast and islands The Classified European Landslide Susceptibility map v1.0 (ELSUS1000, 1 1 km resolution) covers 26 EU member states, Norway and Switzerland as well as the non-eu Balkan countries. The European landslide susceptibility map represents the spatial likelihood of landslide occurrence in five classes: very low, low, moderate, high and very high, as a 1 km raster data set. Croatian territory was also analyzed within ELSUS1000 and it was evaluated, reviewed, updated and improved with regional data sets. Since there is no uniform landslide inventory for the whole territory of Croatia, experience and knowledge of experts about characteristic landslide occurrences for each region were taken into consideration and as a result Landslide susceptibility map of Croatia (LSMC) was created. 551

4 SIG 2016 International Symposium on Engineering Geodesy, May 2016, Varaždin, Croatia The comparison of existing ELSUS map with LSMC [Figure 1.3] displays slight overrating of the landslide susceptibility in Croatian territory by ELSUS. Besides that, the resulting LSMC map is considered to have more appropriate locations of highly susceptible areas that are not exclusively related to the steepest slopes and areas with unfavorable climate. The LSMC map can be considered as a second-approach landslide susceptibility map. With every further step (analysis) the existing landslide susceptibility map must be improved and must become more reliable, accurate and detailed in scale. Next step in this direction could be usage of regional models for landslides within Croatia in map development. The final goal for the future, is the development of landslide susceptibility maps that can be used with great confidence in civil engineering and urban planning. To achieve this, priority should be on the development of a landslide inventory for the whole territory of Croatia. These data could then be used to analyze landslide susceptibility, hazard and risk [Podolszki et al. 2015]. Figure 1.3 Landslide susceptibility map of Croatia: (a) according to ELSUS and (b) according to LSMC 2. Pix4D Pix4D was founded in 2011 in Switzerland [URL 2]. The purpose of the newly formed company was to make software that would provide a professional tool for processing data obtained by using unmanned aircrafts. It started as a spin-off company and the EPFL (Ecole Polytechnique Federale de Lausanne) Computer Vision Laboratory in Switzerland [URL 3] which is one of the two Federal Institutes of Technology. Pix4D is a growing company in collaboration with partners from industry and science involved in many research projects supported by the Swiss government. The company headquarters is now located in Switzerland, and it also has offices in the United States and China. 552

5 2.1. Pix4Dmapper TS 6 New Technologies in Engineering Geodesy and Multisensor Systems Pix4Dmapper is the software that automatically processes the images that were taken from the air using unmanned aircraft, or from the ground with digital camera. It uses technology that works on the principle of recognizing the image content (pixels) in order to make a complete 3D model of the subject [Figure 2.1]. The software is completely adaptable to all types of cameras and image processing results can be converted and used by any GIS or CAD applications. Pix4Dmapper can be used in many different branches of industry and science, such as mining, agriculture, geodesy, civil engineering, management of natural resources and emergency services, and allows the following: line and polyline measurement (break lines), making longitudinal and cross sections, contour drawing, measuring areas and volumes directly in the model and their export to other different formats generating 3D point cloud, true orthomosaic and orthophoto maps, 3D textured models, DSM (Digital Surface Model), NDVI Maps (normalized difference vegetation index) from vertical and oblique aerial or terrestrial photos it uses a fully automated flow of data processing and calibration of each photo in order to achieve a satisfactory level of accuracy, but also the "Rapid Check mode" for checking the quality of recording directly on the field. 3. DJI Phantom 2 Vision+ Figure 2.1 Pix4Dmapper user interface Company DJI [URL 4] is one of the global leaders in the development and production of simple to use and reliable small unmanned aircraft for commercial 553

6 SIG 2016 International Symposium on Engineering Geodesy, May 2016, Varaždin, Croatia use and recreation. The company has more than 500 employees and is one among the largest in the market. Model Phantom 2 Vision+ is one of the top sellers, most simple and very easy to use. Unfortunately, its production has been terminated, but was replaced with newer versions like Phantom 3 and Phantom 4, while technology and other operating principles on new drones remains the same or slightly enhanced. This UAV (unmanned aerial vehicle) has four propellers (quadcopter) and is equipped with a camera attached to the bottom that can record high-resolution images or high-definition video [Figure 3.1(a)]. It also comes with many other features for recording digital imagery. A user can control the device using a remote control connected to almost every smartphone, where live video from the drone s camera can be streamed. By using images supplied to the smartphone, pilots can navigate the drone even when it is out of a direct line of sight. Phantom 2 Vision+ features a stabilized camera mount called a gimbal [Figure 3.1(b)]. Motors on each of its three axes allow the camera to remain steady as the drone moves. For example, if the drone rolls clockwise, the gimbal automatically rotates the camera a corresponding amount counterclockwise to help produce a smooth photo or video. 554 Figure 3.1 (a) & (b) Parts of DJI Phantom 2 Vison+ 4. Mapping notch Doljan landslide with Phantom 2 Vision+ Notch Doljan is situated in km , railway track R201 Zaprešić Čakovec between railway stations Novi Marof Turčin. The instability in the form of the landslide occurred on the right side of the notch. The section of this railway track is situated for the most of its length in distinctly mountainous area and in different elevations, mainly in unfavourable characteristics of the soil (marl-clay) [Figure 4.1]. The purpose of the project was to develop a remediation and reparation design in this location that would ensure permanent stability of the notch.

7 TS 6 New Technologies in Engineering Geodesy and Multisensor Systems Figure 4.1 Picture of landslide taken from DJI Phantom 2 Vison+ Collection of 3D data by conventional surveying methods in special cases can be quite time-consuming, and even dangerous for the field operator. Steep locations like embankments and cuts, vertical notches and locations where potential landslides or mudslides are could be given as an example. In such locations, visual inspection of the terrain as geodetic data collection by classical methods, can result in incomplete and insufficiently detailed display of the terrain. The use of drones in these locations can greatly complement, enhance and even completely replace the classical methods of mapping, determining the volumes, cross-sections, contours and other parameters that are necessary for the remediation of such locations. Upon the arrival at the field it is not required to approach the hazardous location, but come to a safe proximity and send unmanned aircraft (with a preprogrammed flight or manually guided) to collect the data needed for quality and correct visualization and interpretation Field work The first step upon the arrival at the location is to prepare the autonomous flight of the aircraft, which is done by connecting a smartphone with the drone through wireless connection, and upload the map of the location to the smartphone. 555

8 SIG 2016 International Symposium on Engineering Geodesy, May 2016, Varaždin, Croatia Figure 4.2 Loaded map on a smartphone or tablet To prepare autonomous flight it is needed to set up dimensions of the mapping area, flight orientation and altitude as well as drone airspeed. With these certain parameters defined in application Pix4Dcapture for smartphones [URL 5], autonomous flight can start and the application is automatically generating the flight plan, and the positions at which the camera will take photos [Figure 4.2]. With this kind of set up a drone is ready to take flight which is done with a push of a button. When taking pictures from air is done, drone returns to the position from where it started (home point). Upon returning, downloading of geocoded photos and all necessary parameters needed for orientation of images as they were at the time of exposure on the smart phone or tablet computer, begins Office work By uploading the geocoded images taken from air in Pix4Dmapper, flight path and the position of each photo that was taken [Figure 4.3] are displayed. Photo processing, generating point cloud and orthophoto map take place automatically by SFM algorithm (Structure From Motion) by Pix4Dmapper. Depending on the power of the processor and graphics performance of a computer, after some time the software generates orthophoto map and Digital Surface Model (DSM) [Figure 4.4], and 3D view of the terrain in the form of a point cloud [Figure 4.5] 556

9 TS 6 New Technologies in Engineering Geodesy and Multisensor Systems Figure 4.3 Flight plan and positions where images were taken Figure 4.4 Ortophoto map and Digital Surface Model (DSM) generated by Pix4Dmapper from photos taken from air Figure 4.5 Point cloud generated by Pix4Dmapper from photos taken from air 557

10 SIG 2016 International Symposium on Engineering Geodesy, May 2016, Varaždin, Croatia The result of this way generated point cloud and orthophoto maps is their full measurability. This allows us to produce longitudinal and cross sections [Figure 4.6], contour drawing, measuring areas and volumes directly in the point cloud model, [Figure 4.7] and their export to other different CAD format (Computer Added Design) that are used in most professions related for mapping and design. Figure 4.6 Cross section generated in Pix4Dmapper 558 Figure 4.7 Volume generated in Pix4Dmapper

11 TS 6 New Technologies in Engineering Geodesy and Multisensor Systems 5. Conclusion In the above presented case of landslide mapping with DJI Phantom 2 Vision+ and data processing with Pix4D, it has been shown that low-cost UAVs can deliver high-resolution remote sensing data on landslides that are increasingly appearing in Croatia. Compared to conventional classical methods for mapping landslide locations, new technologies and software can save a lot of time and money especially when the area of interest is hazardous and dangerous. The application of unmanned aerial vehicles is in many scientific and research fields of study like remote sensing, civil engineering, archeology, transport, search and rescue etc. It can be easily adjusted to user needs and can be equipped with different types of sensors like Infrared camera or gas detector. However, regardless of all advantages for mapping, UAVs have some disadvantages. They can t be used for measurement in all weather conditions (strong wind, rain), in case of the fall or damage they can cost a lot of money, in case of bad controlling UAV can crash which can endanger in casualties. References Cruden, D.M. (1991). A Simple Definition of a Landslide, Bulletin of the International Association of Engineering Geology, No. 43, pp Jurak, V.; Matković, I.; Miklin, Ž.; Mihalić, S. (1996). Data Analysis of the Landslides in the Republic of Croatia: Present State and Perspectives. Croatian, 7th International Symposium on Landslides, Trondheim, June, Balkema, pp Podolszki, L.; Pollak, D.; Gulam, V.; Miklin, Ž. (2015). Development of Landslide Susceptibility Map of Croatia, G. Lollino et al. (eds.), Engineering Geology for Society and Territory Vol. 2, Landslide Processes, One out of eight IAEG XII Congress volumes on the occasion of the 50th anniversary of IAEG, September, 2014, Torino, pp URL 1: USGS - U.S. Geological Survey, Federal Source for Science about the Earth, Its Natural and Living Resources, Natural Hazards, and the Environment., ( ). URL 2: Pix4D, ( ). URL 3: École polytechnique fédérale de Lausanne, ( ). URL 4: DJI, ( ). URL 5. Pix4Dcapture, ( ). 559

12 SIG 2016 International Symposium on Engineering Geodesy, May 2016, Varaždin, Croatia Primjena bespilotnoga zrakoplovnog sustava za kartiranje klizišta Sažetak. Klizišta su svjetski fenomen koji mogu imati snažan ekonomski utjecaj na infrastrukturne objekte, a ponekad i tragično rezultirati s ljudskim žrtvama. Postoji puno faktora koji utječu na klizanje terena, a neki od njih su sustav odvodnje ili uklanjanje vegetacije, koji se mogu kontrolirati, ali i drugi koji se ne mogu kontrolirati kao npr. lokacija, nagib terena i sastav tla. Nepristupačnost i kartiranje takvog terena često može biti vrlo opasan, skup i dugotrajan. Uporabom bespilotnih zrakoplovnih sustava (engl. UAV Unmanned Aerial Vehicle) koji se koriste za prikupljanje fotografija visokih rezolucija mogu se fotogrametrijskim postupcima izraditi digitalni modeli terena (engl. DTM Digital Terrain Model) klizišta. U vrlo kratkom vremenu na takvim modelima terena moguće je generirati volumen, površinu, slojnice, poprečne i uzdužne presjeke. U ovom radu dan je primjer suvremenog daljinskog kartiranja klizišta pomoću bespilotnog zrakoplovnog sustava DJI Phantom 2 Vision+, te Pix4Dmapper programskog paketa na željezničkoj pruzi R201 Zaprešić Čakovec između kolodvora Novi Marof Turčin na kilometru Ključne riječi: bespilotni zrakoplovni sustav, digitalni model terena, klizište, Phantom 2 Vision+, Pix4Dmapper. *professional paper 560