Damage survey of Eastern Japan Earthquake by Mobile LiDAR

Transcription

1 Damage survey of Eastern Japan Earthquake by Mobile LiDAR Shuhei Hatake 1, Masahiro Ikubo 1, Tatsuya Ikeda 1 1Asia Air Survey Co., ltd. Manpukuji 1-2-2, Asao-ku, Kawasaki, Kanagawa , Japan Keywords: MMS (Mobile Mapping System), The 2011 off the Pacific coast of Tohoku Earthquake, airborne LiDAR, DMC image, LaserMapViewer, recover, restoration 1. Introduction On 11 th March 2011, Great Earthquake of M9.0 occurred the Tohoku district Pacific Ocean. In the 21st century, this earthquake ranks second to the Sumatra earthquake and the Indian Ocean Tsunami of M9.1 (2004). A total of 19,867 persons' damage has been reported to casualties and a missing person by the big earthquake (as of August). Many earthquakes have occurred in Japan, these days. For example, the 1997 Kobe earthquake, the 2004 Chuetsu earthquake, the 2007 Noto-Hanto earthquake and the Chuetsu offing earthquake, and 2008 Iwate and the Miyagi inland earthquake. 1

2 Eurasian Continent Hokkaido Korea Peninsula Tohoku district Sendai Onaga Epicenter Kanto district Itako Japan Trench Pacific Ocean Google earth Figure 1 Location map Japan has many natural disasters, they have put a lot of expenses into maintenance of the civil -works institution of a bank, a breakwater (i.e., a fort can be thought), a dam, etc., so that public works are seen more than the foreign country. Since the catastrophe was an unexpected scale which exceeds design criteria, many houses and institutions were destroyed and many people who could not escape were sacrificed. However, expenditures for public works were reduced by the bubble economy breakdown after As a result, a policy shifts from a hard measure to a soft measure which is gazing at the disaster reduction by maintenance of the hazard map for evacuation action, or initial action correspondence. As a measure of the survey industry, airborne LiDAR was performed immediately after It is because 2

3 the investigation is quick and the amount of change of geographical feature is calculated with high precision. As a result, the geospatial base data made of airborne LiDAR have been fixed 180,000-square km which is around half of national area by national strategy. Moreover, investigation by Mobile Mapping System (MMS) began to work by Japan for public facilities, such as a road, a bridge, and a tunnel, from last year. Japanese infrastructures were built at the rapid economic growth of the 1960s about 50 years ago, and they have seen super-aging periods, such as concrete degradation. About the survey of dilapidated structures, MMS is chosen as one of the non-contact type inspections. In this paper, author notes about the investigation activities immediately after this great earthquake, and describes about grasp of the disaster phenomenon especially by MMS. 2. Damage situation of Earthquake(The 2011 off the Pacific coast of Tohoku Earthquake) The 2011 off the Pacific coast of Tohoku Earthquake occurred near the about 130-km east-northeast of the Ojika peninsula as the focus at 14:46 on March 11, It is a Subduction zone earthquake near the Japan Trench with a deepest 8020m depth and caused three huge destructions. The epicentral area was crossed to a large area about 200km in width and about 500 km in length, in off the Pacific Ocean from the Tohoku district to the Kanto district. 7 prefectures were applied for the Disaster Relief Law. The Tohoku district has been recognized to be a tsunami hazard and the Kanto district with the weak geological foundation has been recognized to be a seismic hazard. The Fukushima nuclear power generation accident was added as a secondary disaster Tsunami on Tohoku district Sanriku coast is a ria shoreline and consists a lot of large and small bays. There was one of the three major fisheries in the world in the offshore. Fishermen had installed seaweed nets or fixed fishing nets into sea. Tsunami attacked also to Kesennuma which was famous fishery base, the catastrophic fires of the secondary disaster brought about disappearance of the town. About 20m 3

4 tsunami attacked in Onagawa town and Rikuzen-Takata town, and the building of 3 stories was beaten. The low plain spread in the Sendai bay southern coast, and it did flood damage over about 10 km to inland. Although the windbreak trees (coastal forest) which planted pine trees, they were run out by the influence wave of tsunami to the sea side. Sendai Airport was also located in this area and the airplanes for aerial photograph were also damaged. These economic amounts of a loss are guessed to be 24 trillion yen Liquefaction of Kanto district The Kanto district is the soft ground which the volcanic ashes called a loamy layer of the Kanto Plain are composed. Furthermore, it consists of the artificial coasts which land filled in shoreline of Tokyo Bay. Therefore, geology is vulnerable. Since the shake continuation time of this earthquake continued 200 seconds or more, liquefaction caused damage to the housing building of about 12,000 households in 1 capital 5 prefectural 64 cities, towns and villages (especially Urayasu-city and Asahi city, Chiba prefecture). Liquefaction was also seen in western Kanagawa where an author lives in. Although there are new houses and apartments, it was farm before construction. Although it conformed to the earthquake-resistant criteria of the Building Standards Act revised in 1981, the building suffered a great deal of damage. On the other hand the skyscrapers built in the Tokyo Bay waterfront have taken in base isolated system (quake-absorbing structure) and the residence of the upper-layers story did not feel the shake with the seismic intensity of five. 3. Survey missions 3-1.Initial airborne survey by Government (Local district government and National land and transportation ministry). Asia Air Survey (AAS) carried out aerial survey from the day following an earthquake disaster 4

5 according to the request of Miyagi prefecture, Iwate prefecture, and the Ministry of Land, Infrastructure, Transport and Tourism (MLIT). We used three sets of Digital Metric Camera (DMC) for aerial photogrammetry survey, and acquired the aerial photo with a resolution of 20 cm. Furthermore, we estimated area of flood distribution by tsunami, and made polygon data of destroyed debris boundary. Table1 Enforcement amount of aerial survey Aireal sencing Survey date Miyagi Iwate Total Aerial Digital Photo 2011/3/13~3/ km km km 2 Oblique Photo 2011/4/5~4/6 300cuts 100cuts 400cuts 2011/3/17~4/5 Airborne LiDAR 2011/4/5~4/ km 2 600km km 2 All values are approximate Furthermore, according to request of local municipalities and MLIT, airborne LiDAR survey was carried out from March 17 after six days. It was carried out quickly by one ALS50 system and one ALS60 system load Cessna 208. There was most survey range of us in aviation survey companies. Heliborne Lidar was partially supplied to the measurement of the river bank of the Kitakami river or Kasumigaura by MLIT. Airborne LiDAR data was immediately processed as colored maps or crossing profiles. We contributed urgent reconstruct work of earthquake disaster. 3-2.AAS Original tool AAS used the geospatial information processing tool which it was original and was developed, in order to process these missions quickly and to distribute data early. The outline is shown below. (1)Web photogrammetryheight This system was utilized for detailed grasp of debris region. This work was carried out the calculation the amount of debris of each cities, towns and villages by the request of one municipality. Strictly speaking about this job, many operators accessed one server and made temporary debris map at once. Therefore AAS decided to adopt this system, because there was no copy time of the DMC images used for stereo mapping. This tool was developed a few years ago. The functions have stereo 3D vision of digital pictures through the Web, which simply measure the distance and height. It means that this is a good equivalent to the viewer for customers. However, the mapping engineers had many issues of a display and operability during working. Anymore the developer has improved according to the request from 5

6 operators. (2)LV square In this earthquake disaster correspondence, aerial photographs, oblique photographs, aerial LiDAR data, and MMS data were acquired for a short period of time. It not only is storing these important data, but I suppose it is a shortcut of revival for various persons to utilize. For that purpose, it is necessary to establish the excellent communication-of-information technology. LV Square is the information-sharing platform which used the sky and a ground picture, and map information as the base. It has functions to take data simply, and to distribute data without load PC of a client. By introducing this system, the information needed for restoration works have been offered quickly using pinpoint picture and character. 4. MMS Survey Table1 Specification of Streetmapper(AAS) 4-1.GeoMASTER Neo Issue Remarks AAS was installed MMS on 7 th Vehicle Toyota Rush1500cc:compct mini-van GNSS 12channel L1/L2, 2Hz March before this earthquake IMU TerraControl happened. AAS members were Degree RMS Heading:0.01,Roll/Pitch:0.004 Laser RIEGL VQ250 2pcs received the MMS tutorial on 11 th Pulse Reception rate 300KHz/ scanning rate:100scans/s March. GeoMasterNeo is a Point density(40km/h) 900points/m2(range 5m) Odometer Optical vehicle loaded on StreetMapper Digital camera 1.2M Nikon & Olympus which has purchased from 3D Omni directional camera LadyBug3 Laser Mapping (British) & IGI(German). The specification is shown in Table1. It sets dual laser scanners (Reigl VQ250) which has 300KHz of max transmit rate. The capability of laser is the most laser point density in Japan, which is able to acquire high points cloud which is 3D coordinate of ground features which has been measured by stop & go method using terrestrial LiDAR or Total-station. That is, MMS measurement has a merit which can work safely for a short period of time, without restricting traffic. The structure of GeoMasterNeo is shown in Figure 2. At first, an IMU (Inertial Motion Unit) and Global Navigation Satellite Systems (GNSS) compute the position and orientation of vehicle. The point cloud of reflective intensity like the black-and-white picture shown in Fig.2 as an example can be created. Furthermore, if it combines with digital camera pictures, the point cloud with color as shown can be created. 6

7 IMU GNSS Receiver Rangeing Image Capture Gyro sensor Odo-meter GNSS Antenna Laser Scanner 360 Omnidirectional camera 16Ma digital camera Omni-directional 全天周カメラ camera Calculation position and orientation of vehicle 16Ma Digital 高詳細カメラ camera Laser Scanner Generate point cloud of intensity Generate point cloud with color Application of Point Cloud Figure2 Concept of GeoMasterNEO 360 Laser Scan Like people's vision, reflective intensity has the feature which can display a bright thing as white or a dark thing as black. If this character is used, a white line (ex. zebra crossing) and a manhole can be checked clearly. The position of a manhole serves as important information in the case of renewal of a sewer ledger. The position accuracy of height and horizon has been achieved the results of 5 cm over the place where GNSS is good. The level accuracy of the map scales 1/500 of Japanese public regulation is 25 cm. It can be said to be sufficient accuracy used also for measurement of a large scale map. 4-2.Missions MMS measurement with aerbone LiDAR (1 pt/m2) for understanding the detail of destructive civil structure, such as a bank and shore protection, was implemented to acquire data from two below areas in April; (1) Liquefaction survey in Kasumigaura lake On April 1, we carried out MMS measurement in Itako city located in the mouth of Kasumigaura (refer to Figure1). In the Hinode Town in the city, much damage caused by liquefaction had risen to the dwelling house or the road. Many construction 7

8 vehicles for restoration of lifelines (such as electricity, water service and gas) were seen on the day. Especially I was very much surprised at the situation where many telegraph poles had fallen, because the paved road portion of the municipal road rose by liquefaction. In addition, the cover concrete board on an irrigation canal inclined toward the road, and the big cracks of the road surface were often seen. (2) Tsunami survey in Miyagi It was measured areas from the Southern side of Watari-town to the Northern side of Kesennuma-town, Miyagi Prefecture since April 20 th to 24 th. We measured the destroyed river bank in the Abukuma river Mouth in Watari. Most customer desire to check the detailed (3D) breakage situation of the bankside in order not to detect the situation from right above, even from airborne Lidar. we have acquired the breakage situation of shore protections and the fishery institutions of the fishing port in Onagawa where was strucked by approximately 20m Linkage with Image Intensity(right) wave. In Ishinomaki where the port suffered from the damage and in Kesennuma where the town disappeared by the fire, we also measured the dispersion situation and discarded situation of debris. 4-3.Visualization tool AAS could be rapidly processed cloud points data, which are high density and large size, acquired by GeoMasterNeo, and developed LaserMap Viewer.It is a key how surveyor provides a customer this huge data. AAS has been developing LaserMapViewer which can display at high speed the massive data acquired by GeoMasterNeo. The function of LaserMapViewer is outlined 4Screen display Cross section Only road display(right) Area display 8 Horizontal measurement MMS & airborne LiDAR Figure3 Main functions of LaserMapViewer

9 below. (1) Function of High speed display The size of the data acquired by GeoMasterNeo becomes large in proportion to measurement distance. The viewer can always expand and reduce about laser points of 10 million smoothly, and a viewpoint can move and rotate freely. (2) Function of multi display The display is equipped with the function which can be seen from many viewpoints. It can display from a maximum of 4 directions, and can find out a subject from various directions. Since it is also possible to give restriction to the height to display, buildings and electric-wires can be extracted and roads can only be displayed. The function of cross-sectional display can generate arbitrary sections, and also has a function to which horizontal displacement of the cross-sectional line is carried out at a fixed interval. Therefore, it is also possible to generate more sectional views in the every place point of a road. Furthermore, any data except GeoMasterNeo data can be treated by LaserMapViewer. For example, the combined airborne LiDAR and MMS data can be displayed too. (3) Function of linkage GeomasterNeo owns Ladybug3 of omnidirectional camera in addition to two digital single lens reflex cameras. The ominidirectional pictures are processed as a LiveView picture, and can be displayed as one of the multi-expression functions. Moreover, it is possible for the display of images to also make it synchronize with point cloud display. (4) Function of measurement In addition to measurement between two points, vertical and horizontal value and amount of an angle and area are possible for a measurement function. During measurement, since an auxiliary conductor and a measurement value are displayed in real time, miss-measurement can be prevented. 5. Consideration A future of MMS survey is expected for broad practical use out of disaster investigation. The practical use is renewal of a road ledger and a sewer ledger, application to road disaster prevention, roadside tree investigation, bridge check, electric wire management, city planning, a railroad, and the river field. We have called the primary process data proceesing from colored from GPS/IMU analysis to 9

10 generaing laser point with color. Now, this processing has taken 6 times as much time as measurement (if it is one-day measurement, processing takes the six days). A labor is spent more on road mapping of the following process. Although fieald survey is quick, it is a problem that indoor processing work increases and expense becomes higher than the conventional technique. In fact data is highly precise and quality, but it is necessary to consider the effect of cost -benefit. In conclusion, it is necessary for such emergency plan to build capacity development by developing the mapping software such as LasermapViewer and introducing 64-bit personal computer etc. 6. Conclusion East Japan great earthquake immediately after it was introduced in my company. The acquired data was introduced to SPAR and also known to the United States. The destructive energy from Tsunami is very challenging for researcher of engineer and architectures to reconsider the method of measuring tremors and shocks and undulatory movements of earthquakes. We provided requested cloud points data to a special team led by Oregon University which specialize in Tsunami. Thus, point clouds data from MMS is worth to immediately collect in an earthquake disaster. I wish that those data could be utilized for various scientific fields without only use of photography. 7. Acknowledgement I appreciate so much for many corporate and help from oversea. I send our deep and abiding sympathy and prayers to the victims of this earthquake. 10