• Journal of the Korean Society of Industry Convergence
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• v.24 no.6_2
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• pp.753-762
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• 2021

Google provides mapping services using satellite imagery, this is widely used for the study. Since about 20 years ago, research and business using drones have been expanding. Pix4D is widely used to create 3D information models using drones. This study compared the distance error by comparing the result of the road construction site with the DSM data of Google Earth and Pix4 D. Through this, we tried to understand the reliability of the result of distance measurement in Google Earth. A DTM result of 3.08 cm/pixel was obtained as a result of matching with 49666 key points for each image. The length and altitude of Pix4D and Google Earth were measured and compared using the obtained PCD. As a result, the average error of the distance based on the data of Pix4D was measured to be 0.68 m, confirming that the error was relatively small. As a result of measuring the altitude of Google Earth and Pix4D and comparing them, it was confirmed that the maximum error was 83.214m, which was measured using satellite images, but the error was quite large and there was inaccuracy. Through this, it was confirmed that there are difficulties in analyzing and acquiring data at road construction sites using Google Earth, and the result was obtained that point cloud data using drones is necessary.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.12
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• pp.1739-1741
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• 2016

A compressive sensing based iterative scheme for reducing both the impulsive noise as well as the clipping noise is proposed for OFDM-based communication systems. Nonlinear blanking using adaptive thresholds is used in the 1st stage followed by two consecutive compressive sensing based detection with the aid of decision feedback for reducing the BER gradually. Our simulation results revealed an SNR gain of 4.5dB at the BER of $10^{-5}$.

• Korean Journal of Remote Sensing
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• v.36 no.5_4
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• pp.1195-1207
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• 2020

With the development of GeoWeb technology, 2D/3D spatial information services through the web are also has been used increasingly in the application of disaster management. This paper is suggested to construct a web-based 3D geo-spatial information mapping platform to visualize various spatial information collected at the disaster site in a web environment. This paper is presented a web-based geo-spatial information mapping service plan for the various types of 2D/3D spatial data and large-volume LiDAR point cloud data collected at the disaster accident site using HTML5/WebGL, web development standard technology and open source. Firstly, the collected disaster site survey 2D data is constructed as a spatial DB using GeoServer's WMS service and PostGIS provided an open source and rendered in a web environment. Secondly, in order to efficiently render large-capacity 3D point cloud data in a web environment, a Potree algorithm is applied to simplifies point cloud data into 2D tiles using a multi-resolution octree structure. Lastly, OpenLayers3 based 3D web mapping pilot system is developed for web visualization of 2D/3D spatial information by implementing basic and application functions for controlling and measuring 3D maps with Graphic User Interface (GUI). For the further research, it is expected that various 2D survey data and various spatial image information of a disaster site can be used for scientific investigation and analysis of disaster accidents by overlaying and visualizing them on a built web-based 3D geo-spatial information system.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.37 no.4
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• pp.345-353
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• 2004

Target strength (TS) of Japanese common squids (Todarodes pacificus) were measured using 38 and 120 kHz split beam scientific echosounders under the live condition. For the TS measurement of an individual, a total of 3 squids (mantle length (ML): 22.8, 25, and 27 cm) were used using small fishhook method, whereas for measurement of swimming angle, a total of 8 squids (ML: 21-27 cm) were used under live condition, confined with net cage with 2 m diameter At the same time, two underwater video cameras enabled continuous monitoring of squid behavior. Considering normal behavior, the mean TS at 38 and 120 kHz varied from -48.6 to -45.9 dB, and from -46.5 to -44.6 dB, respectively In both frequencies, mean TS at 120 kHz is relatively higher than that of 38 kHz, approximately 1.3-2.5 dB. From free living condition, the mean swimming angle of the squlds was $-24^{\circ}$. The results of the measurement will be provided basic information for conducting acoustic surveys of the squid.

• Korean Journal of Remote Sensing
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• v.38 no.5_3
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• pp.887-899
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• 2022

Drought caused by meteorological factors negatively affects vegetation in terrestrial ecosystems. In this study, the state in which meteorological drought affects vegetation was defined as the ecological drought of vegetation, and the ecological drought condition index of vegetation (EDCI-veg) was proposed to quantitatively monitor the degree of impact. EDCI-veg is derived from a copula-based bi-variate joint probability model between vegetation and meteorological drought information, and can be expressed numerically how affected the current vegetation condition was by the drought when the drought occurred. Comparing past meteorological drought events with their corresponding vegetation condition, the proposed index was examined, and it was confirmed that EDCI-veg could properly monitor the ecological drought of vegetation. In addition, it was possible to spatially identify ecological drought conditions by creating a high-resolution drought map using remote sensing data.

• Proceedings of the KSRS Conference
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• 2008.10a
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• pp.274-276
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• 2008

At the stage of content convergence into cell phone, technologies for geo-spatial information sharing and searching are being developed. Currently, 2D portable navigation map for mobile navigation is provided by communication companies, but geobrowers for 3D geo-information in cell phone are under developing. In this study, 3D feature transformation among X3D-M3G-KML, on mobile and web environments, is dealt with as the first stage for the further mobile 3D web application. As well, it is possible to real-time interoperable 3D geo-information exchange issues within both environments.

• Korean Journal of Remote Sensing
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• v.28 no.2
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• pp.245-253
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• 2012

The public and civilian demands regarding 3D geo-spatial information processing on mobile device including smartphone are increasing. But there are few actual implementations or application cases. This work is to present some results by a prototype implementation of 3D terrain information visualization function with satellite image and DEM using HTML5 WebGL, which is a web-based graphic library under the standardization process. This is a useful standard for cross-platform operation for 3D graphic rendering without other plug-in modules. As the results, in the different types of operating system or browser in a personal computer or a smartphone, it shows same rendering results, as long as they support HTML5 WebGL. As well;geo-metadata search and identification functions for data sets for 3D terrain visualization process are added in this implementation for the practical aspect.

• Korean Journal of Remote Sensing
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• v.23 no.3
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• pp.211-219
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• 2007

Building extraction is one of the essential issues for 3D city modelling. In recent years, high-resolution satellite imagery has become widely available and it brings new methodology for urban mapping. In this paper, we have developed a semi-automatic algorithm to determine building heights from monoscopic high-resolution satellite data. The algorithm is based on the analysis of the projected shadow and actual shadow of a building. Once two roof comer points are measured manually, the algorithm detects (rectangular) roof boundary automatically. Then it estimates a building height automatically by projecting building shadow onto the image for a given building height, counting overlapping pixels between the projected shadow and actual shadow, and finding the height that maximizes the number of overlapping pixels. Once the height and roof boundary are available, the footprint and a 3D wireframe model of a building can be determined. The proposed algorithm is tested with IKONOS images over Deajeon city and the result is compared with the building height determined by stereo analysis. The accuracy of building height extraction is examined using standard error of estimate.

• Korean Journal of Remote Sensing
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• v.20 no.6
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• pp.409-418
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• 2004

LOD is a widely used technique in 3D game and animation to represent large 3D data sets smoothly in real-time. Most LOD algorithms use a binary tree to keep the ancestor information. A new algorithm proposed in this paper, however, do not keep the ancestor information, thus use the less memory space and rather increase the rendering performance. To verify the efficiency of the proposed algorithm, performance comparison with ROAM is conducted in real-time 3D terrain navigation. Result shows that the proposed algorithm uses about 1/4 of the memory space of ROAM and about 4 times faster than ROAM.

• Proceedings of the KSRS Conference
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• 2004.10a
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• pp.128-131
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• 2004

In this paper, we describe reconstructed 3D-urban modeling techniques for laser scanner and CCD camera system, which are loading on the vehicle. We use two laser scanners, the one is horizon scanner and the other is vertical scanner. Horizon scanner acquires the horizon data of building for localization. Vertical scan data are main information for constructing a building. We compared extraction of edge aerial image with laser scan data. This method is able to correct the cumulative error of self-localization. Then we remove obstacles of 3D-reconstructed building. Real-texture information that is acquired with CCD camera is mapped by 3D-depth information. 3D building of urban is reconstructed to 3D-virtual world. These techniques apply to city plan. 3D-environment game. movie background. unmanned-patrol etc.