Near real-time GPS applications for tsunami early warning systems

GPS (Global Positioning System) technology is widely used for positioning applications. Many of them have high requirements with respect to precision, reliability or fast product delivery, but usually not all at the same time as it is the case for early warning applications. The tasks for the GPS-based components within the GITEWS project (German Indonesian Tsunami Early Warning System, Rudloff et al., 2009) are to support the determination of sea levels (measured onshore and offshore) and to detect co-seismic land mass displacements with the lowest possible latency (design goal: first reliable results after 5 min). The completed system was designed to fulfil these tasks in near real-time, rather than for scientific research requirements. The obtained data products (movements of GPS antennas) are supporting the warning process in different ways. The measurements from GPS instruments on buoys allow the earliest possible detection or confirmation of tsunami waves on the ocean. Onshore GPS measurements are made collocated with tide gauges or seismological stations and give information about co-seismic land mass movements as recorded, e.g., during the great Sumatra-Andaman earthquake of 2004 (Subarya et al., 2006). This information is important to separate tsunami-caused sea height movements from apparent sea height changes at tide gauge locations (sensor station movement) and also as additional information about earthquakes' mechanisms, as this is an essential information to predict a tsunami (Sobolev et al., 2007). <br><br> This article gives an end-to-end overview of the GITEWS GPS-component system, from the GPS sensors (GPS receiver with GPS antenna and auxiliary systems, either onshore or offshore) to the early warning centre displays. We describe how the GPS sensors have been installed, how they are operated and the methods used to collect, transfer and process the GPS data in near real-time. This includes the sensor system design, the communication system layout with real-time data streaming, the data processing strategy and the final products of the GPS-based early warning system components

Design and development of ocean monitoring system based on GPS

Coastal zone of Malaysia has a vital role in socio-economic and environmental in pursuing the country development. However, it constantly faces a threat from coastal erosion. The report year 2013 from the Department of Irrigation and Drainage Malaysia showed 29% of Malaysian coastal has been experiencing erosion at various levels and primarily driven by ocean waves. Hence, this study focused on developing the ocean monitoring system consists of a buoy with Global Positioning System (GPS) technology, reference station and data analysis techniques. The buoy was developed by considering local factors and improves the performance of existing buoy. Comparison with existing GPS buoy has found that the GPS buoy is far exceeded in term of physical specifications, costs, sensors sensitivity and observation interval. Based on the verification with slider machine, this system has been able to provide high accuracy result less than 0.5 cm compared to the standard value of slider machine. The RMS error from data analysis technique is less than 0.0016 m. Validation with Department of Survey and Mapping Malaysia (JUPEM) automatic tide gauges have found both methods agreed on tidal pattern with small discrepancy of less than 10 cm. Encouraging results were also obtained when the observations off coast Senggarang compared with manual observations, historical data and Malaysia Meteorological Department (MetMalaysia) wave forecasting. This system has been observing the same tidal patterns with data analysis RMS error less than 0.0013 m. Comparison with the height of historical wave data and wave forecast shows the results of observations of this system are in the range of comparisons made. Difference of 20 mm was obtained when compared with the wave height observed manually. The usefulness of GPS buoy data also has been demonstrated in analyzing the monsoon wind influences at off coast Senggarang

SISTEM KOMUNIKASI DATA PADA BAND ULTRA HIGH FREQUENCY (UHF) MENGGUNAKAN PROTOKOL AX-25 UNTUK TSUNAMI EARLY WARNING SYSTEM

Indonesia merupakan negara yang terletak di antara dua lempeng benua sangatlah rentan terhadap bahaya gempa bumi. Sebagian besar gempa yang terjadi di Indonesia berasal dari gempa di dasar laut dengan kekuatan gempa berskala cukup besar sehingga dapat berpotensi menghasilkan tsunami. Tsunami Early Warning System yang telah diaplikasikan pada beberapa daerah di Indonesia tergolong kompleks pada sistem komunikasi datanya. Sehingga, melalui penelitian ini dirancang sebuah sistem komunikasi data menggunakan gelombang radio Ultra High Frequency, serta menerapkan protokol AX-25 sebagai protokol yang digunakan. Hasil yang didapatkan pada penelitian ini adalah system buoy dengan gelombang Ultra High Frequency dan daya 2,4 Watt dapat mengirimkan data ketinggian gelombang dengan jarak 4,28 km dengan pada kondisi Line of Sight (LOS) dengan resolusi hingga 1,5 cm. Jarak yang lebih jauh dapat dilakukan dengan penambahan daya pemancar. Protokol AX-25 dapat mengenkapsulasi data pembacaan sensor sebelum ditransmisikan dan mengdekapsulasikan kembali data tersebut setelah sampai di penerima. Pada pengujian BER untuk jarak 3 km diperoleh nilai error sebesar 0,0069. ================================================================= Indonesia is a country that lies between the two continental plates. This makes Indonesia extremely vulnerable to earthquake hazard. Most of the earthquakes that occurred in Indonesia comes from the earthquakes that occurring below ocean with a large enough magnitude scale so it can potentially generate tsunami. Tsunami Early Warning System which has been applied to several areas in Indonesia is considered complex on communication data system. Therefore, through this research will be designed a communication data system using radio wave by applying AX-25 protocol as the protocol. The results that obtained in this research is the buoy system with Ultra High Frequency waves and 2,4 Watt power can transmit simulated sea wave heights data with a distance of 4,28 km on the condition of Line of Sight (LOS) with 1,5 cm resolution. The longer distance can be accomplished by the addition of transmitter power. The AX-25 protocol can encapsulates the sensor data before being transmitted and decapsulated it's back after arriving at the receiver. On BER test for a distance of 3 km, we obtained 0,0069 error value

Combining thermal imaging with photogrammetry of an active volcano using UAV : an example from Stromboli, Italy

The authors would like to thank the Istituto Nazionale di Geofisica e Vulcanologia – Sezione di Catania (INGV‐CT) for granting permission to conduct the UAV surveys over the Stromboli volcano. This work was supported by the School for Early Career Researchers at the University of Aberdeen, UK. Dougal Jerram is partly funded through a Norwegian Research Council Centres of Excellence project (project number 223272, CEED). The team would like to thank Angelo Cristaudo for logistical help during the fieldwork efforts on Stromboli.Peer reviewedPostprin

Feasibility studies of terrestrial laser scanning in Coastal Geomorphology, Agronomy, and Geoarchaeology

Terrestrial laser scanning (TLS) is a newer, active method of remote sensing for the automatic detection of 3D coordinate points. This method has been developed particularly during the last 20 years, in addition to airborne and mobile laser scanning methods. All these methods use laser light and additional angle measurements for the detection of distances and directions. Thus, several thousands to hundreds of thousands of polar coordinates per second can be measured directly by an automatic deflection of laser beams. For TLS measurements, the coordinates and orientation of the origin of the laser beam can be determined to register different scan positions in a common coordinate system. These measurements are usually conducted by Global Navigation Satellite Systems or total station surveying, but also identical points can be used and data driven methods are possible. Typically, accuracies and point densities of a few centimetres to a few millimetres are achieved depending on the method. The derived 3D point clouds contain millions of points, which can be evaluated in post-processing stages by symbolic or data-driven methods. Besides the creation of digital surface and terrain models, laser scanning is used in many areas for the determination of 3D objects, distances, dimensions, and volumes. In addition, changes can be determined by multi-temporal surveys. The terrestrial laser scanner Riegl LMS Z-420i was used in this work in combination with the Differential Global Positioning System system Topcon Hiper Pro, based on Real Time Kinematic (RTK-DGPS). In addition to the direct position determination of the laser scanner, the position of a self-developed reflector on a ranging pole was measured by the RTK-DGPS system to accurately derive the orientation of each measured point cloud. Moreover, the scanner is equipped with an additional, mounted camera Nikon D200 to capture oriented pictures. These pictures allow colouring the point cloud in true colours and thus allow a better orientation. Furthermore, the pictures can be used for the extraction of detailed 3D information and for texturing the 3D objects. In one of the post-processing steps, the direct georeferencing by RTK-DGPS data was refined using the Multi Station Adjustment, which employs the Iterative Closest Point algorithm. According to the specific objectives, the point clouds were then filtered, clipped, and processed to establish 3D objects for further usage. In this dissertation, the feasibility of the method has been analysed by investigating the applicability of the system, the accuracy, and the post-processing methods by means of case studies from the research areas of coastal geomorphology, agronomy, and geoarchaeology. In general, the measurement system has been proven to be robust and suitable for field surveys in all cases. The surveys themselves, including the selected georeferencing approach, were conducted quickly and reliably. With the refinement of the Multi Station Adjustment a relative accuracy of about 1 cm has been achieved. The absolute accuracy is about 1.5 m, limited by the RTK-DGPS system, which can be enhanced through advanced techniques. Specific post-processing steps have been conducted to solve the specific goals of each research area. The method was applied for coastal geomorphological research in western Greece. This part of the study deals with 3D reconstructed volumes and corresponding masses of boulders, which have been dislocated by high energy events. The boulder masses and other parameters, such as the height and distance to the current sea level, have been used in wave transport equations for the calculation of minimum wave heights and velocities of storm and tsunami scenarios and were compared to each other. A significant increase in accuracy of 30% on average compared with the conventional method of simply measuring the axes was detected. For comparison, annual measurements at seven locations in western Greece were performed over three years (2009-2011) and changes in the sediment budget were successfully detected. The base points of the RTK-DGPS system were marked and used every year. Difficulties arose in areas with high surface roughness and slight changes in the annual position of the laser scanner led to an uneven point density and generated non-existing changes. For this reason, all results were additionally checked by pictures of the mounted camera and a direct point cloud comparison. Similarly, agricultural plants were surveyed by a multi-temporal approach on a field over two years using the stated method. Plant heights and their variability within a field were successfully determined using Crop Surface Models, which represent the top canopy. The spatial variability of plant development was compared with topographic parameters as well as soil properties and significant correlations were found. Furthermore, the method was carried out with four different types of sugar-beet at a higher resolution, which was achieved by increasing the height of the measurement position. The differences between the crop varieties and their growth behaviour under drought stress were represented by the derived plant heights and a relation to biomass and the Leaf Area Index was successfully established. With regard to geoarchaeological investigations in Jordan, Spain, and Egypt, the method was used in order to document respective sites and specific issues, such as proportions and volumes derived from the generated 3D models were solved. However, a full coverage of complexly structured sites, like caves or early settlements is partially prevented by the oversized scanner, slow measurement rates, and the necessary minimum measurement distance. The 3D data can be combined with other data for further research by the common georeference. The selected method has been found suitable to create accurate 3D point clouds and corresponding 3D models that can be used in accordance with the respective research problem. The feasibility of the TLS method for various issues of the case studies was proven, but limitations of the used system have also been detected and are described in the respective chapters. Further methods or other, newer TLS systems may be better suited for specific cases

Space-borne application of GNSS reflectometry for global sea state monitoring

This research focuses on modelling the relationship between wind conditions, sea roughness and GNSS reflections received from Low Earth Orbit (LEO). The motivation for this study lies in the recent development of a GNSS reflections receiver platform for the UK-DMC satellite and the numerous advantages proposed GNSS Reflectometry can provide in Earth Observation and global disaster monitoring. The fIrst part of the thesis focuses on the simulation procedure of received GPS-R Delay-Doppler Map (DDM). Airborne GPS-R scatterometric model has been adapted into this space-borne application research. Aft~r deriving DDM simulations according to reflection scenario, the results of two-dimensional data-model fItting are presented and analysed. The sensitivity discussion of current GPS-R model suggests some limitations of the modelling method, especially under medium and high wind speed ranges. In the second part, we investigate the inversion scheme of DDMs for the purpose of extracting a statistical wave model empirically. The similar model structure of DDM simulation is used but the processing order is turned over. After deconvolution, DDMs are inversed back to spatial energy maps and spatial slope probability maps. Three inversion algorithms are developed and compared. Preliminary synthetic and real data experiments give evidence of the feasibility of the inversion methodology. Finally, in the third part of this research, a new geometric wave slope statistical model is discussed in the context of wave fIeld simulations. The sensitivity of obtained statistical model is discussed in terms of wind speed, wave direction and observing incident angle. This provides an alternative view point to look into the wave slope probability properties and compensate the traditional theoretic and empirical wave modelling methods. Key words: GNSS-Reflectometry, Delay-Doppler Map inversion, wind conditions, sea surface roughness, slope probability density function, statistical wave slope model.EThOS - Electronic Theses Online ServiceGBUnited Kingdo