• Tunnel and Underground Space
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• 제27권1호
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• pp.58-68
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• 2017

According to the development of optical technology, the capacity of LIDAR equipments has been greatly improved to get rock mass characteristics precisely and accurately enough and it has been lightened and popularized so that it can be easily used in the field. In this study, we examined the applicability of roughness measurement for joints in a rock slope using LIDAR technique. A triangular irregular network was constructed using LIDAR and a patch, which is a plane structure of discontinuity on rock mass measured from LIDAR scanning, was extracted to estimate the roughness of the rock slope. Four different kinds of roughness parameters were analyzed to find out their correlation with JRC for various point intervals. Among them, $R_s$ parameter was used to measure the roughness of a patch. Regression analysis between four roughness parameters and JRC with respect to point interval was performed. All the roughness parameters decreased with the increase of point interval. In addition, the parameter value showed greater decrease for rougher surfaces. A method of roughness measurement using $R_s$ parameter on rock slope discontinuities was suggested which showed slight overestimation of the real roughness value.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제10권4호
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• pp.693-699
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• 2006

Digital airborne image must be precisely orthorectified to become geographical information. For orthorectification of airborne images, GPS/INS (Global Positioning System/Inertial Navigation System) and LIDAR (LIght Detection And Ranging) elevation data were employed. In this study, 635 frame airborne images were produced and LIDAR data were converted to raster image for applying to image orthorectification. To derive images with constant brightness, flat field correction was applied to images. The airborne images were geometrically corrected by calculating internal orientation and external orientation using GPS/INS data and then orthorectified using LIDAR digital elevation model image. The precision of orthorectified images was validated by collecting 50 ground control points from arbitrary five images and LIDAR intensity image. As validation result, RMSE (Root Mean Square Error) was 0.387 as almost same as only two times of pixel spatial resolution. It is possible that this automatic orthorectification method of airborne image with higher precision is applied to airborne image industry.

• Korean Journal of Geomatics
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• 제5권1호
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• pp.7-19
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• 2005

Photogrammetric mapping procedures have gone through major developments due to significant improvements in its underlying technologies. The availability of GPS/INS systems greatly assist in direct geo-referencing of the acquired imagery. Still, photogrammetric datasets taken without the aid of positioning and navigation systems need control information for the purpose of surface reconstruction. Point features were, and still are, the primary source of control for the photogrammetric triangulation although other higher-order features are available and can be used. LIDAR systems supply dense geometric surface information in the form of three dimensional coordinates with respect to certain reference system. Considering the accuracy improvement of LIDAR systems in the recent years, LIDAR data is considered a viable supply of photogrammetric control. To exploit LIDAR data, new challenges are poised concerning the representation and reference system by which both the photogrammetric and LIDAR datasets are described. In this paper, registration methodologies will be devised for the purpose of integrating the LIDAR data into the photogrammetric triangulation. Such registration methodologies have to deal with three issues: registration primitives, transformation parameters, and similarity measures. Two methodologies will be introduced that utilize straight-line and areal features derived from both datasets as the registration primitives. The first methodology directly incorporates the LIDAR lines as control information in the photogrammetric triangulation, while in the second methodology, LIDAR patches are used to produce and align the photogrammetric model. Also, camera self-calibration experiments were conducted on simulated and real data to test the feasibility of using LIDAR patches for this purpose.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 한국측량학회 2006년도 춘계학술발표회 논문집
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• pp.199-204
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• 2006

Airborne LIDAR systems have been increasingly used for various applications as an effective surveying mean that can be complementary or alternative to the traditional one based on aerial photos. A LIDAR system is a multi-sensor system consisting of GPS, INS, and a laser scanner and hence the errors associated with the LIDAR data can be significantly affected by not only the errors associated with each individual sensor but also the errors involved in combining these sensors. The analysis about these errors have been performed by some researchers but yet insufficient so that the results can be critically contributed to performing accurate calibration of LIDAR data. In this study, we thus analyze these error sources, derive their mathematical models and perform the sensitivity analysis to assess how significantly each error affects the LIDAR data. The results from this sensitivity analysis in particular can be effectively used to determine the main parameters modelling the systematic errors associated with the LIDAR data for their calibration.

• Proceedings of the KSRS Conference
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume II
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• pp.676-679
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• 2006

Mangrove crowns were delineated using active sensor LIDAR (LIght Detection And Ranging) data by a crown delineating model developed in this study. LIDAR data were acquired from airborne survey by a helicopter for the estuary of Macouria in the northeast coast of French Guiana. The canopy height image was derived from LIDAR vector data by calculating the difference between ground and non-ground data. The mangrove site in the study area was classified to three sectors by the time of mangrove settlement; Mangrove 1986, 2002 and 2003. The estimated crown of Mangrove 1986 was reliable defined for their size, number and volume because of larger crown size and bigger variation of crown height. The tree crown size of Mangrove 2002 and 2003 by the model was overestimated and the number of trees was much underestimated. The estimated crown was not for single crown but a crown group due to homogenous crown height and spatial resolution of LIDAR data. However the canopy height image derived from LIDAR data provided three-dimensional information of mangroves.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 한국측량학회 2004년도 추계학술발표회 논문집
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• pp.257-262
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• 2004

The purpose of data fusion is collecting maximized information from combining the data attained from more than two same or different kind sensor systems. Data fusion of same kind sensor systems like optical imagery has been on focus, but recently, LIDAR emerged as a new technology for capturing rapidally data on physical surfaces and the high accuray results derived from the LIDAR data. Considering the nature of aerial imagery and LIDAR data, it is clear that the two systems provide complementary information. Data fusion is consisted of two steps, alignment and matching. However, the complementary information can only be fully utilized after sucessful alignment of the aerial imagery and lidar data. In this research, deal with centroid of building extracted from lidar data as control information for estimating exterior orientation parameters of aerial imagery relative to the LIDAR reference frame.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 한국측량학회 2010년 춘계학술발표회 논문집
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• pp.231-233
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• 2010

Many algorithms for processing LIDAR data are being developed for diverse applications not limited to patch segmentation, bare-earth filtering and building extraction. However, since we cannot exactly know the true locations of LIDAR points, it is difficult to assess the performance of a LIDAR data processing algorithm. In this paper, we thus attempted the performance assessment of the segmentation algorithm developed by Lee (2006) using the LIDAR data generated through simulation based on sensor modelling. Consequently, based on simulation, we can perform the performance assessment of a LIDAR processing algorithm more objectively and quantitatively with an automatic procedure.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 추계학술대회 논문집
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• pp.453-455
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• 2009

The wind speed measurement is performed using SODAR and LIDAR to evaluate availability of remote sensing in assessment of wind resource. The intercomparison comprises time series, correlation analysis and recovery rate. It shows that LIDAR is more effective than using SODAR to measure wind speed in ambient disturbance.

• Journal of Korean Society for Atmospheric Environment
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• 제22권1호
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• pp.1-14
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• 2006

Tropospheric aerosols are highly variant in time and space due to non-uniform source distribution and strong influence of meteorological conditions. Backscatter lidar measurement is useful to understand vertical distribution of aerosol. However, the backscatter lidar equation is undetermined due to its dependence on the two unknowns, extinction and backscattering coefficient. This dependence necessitates the exact value of the ratio between two parameters, that is, the lidar ratio. Also, Iidar ratio itself is useful optical parameter to understand properties of aerosols. Tropospheric aerosols were observed to understand variance of lidar ratio at Anmyeon island ($36.32^{/circ}N$, $126.19^{/circ}E$), Korea using a multi-wavelength raman lidar system developed by the Advanced Environmental Monitoring Research Center (ADEMRC), Gwangju Institute Science and Technology (GIST), Korea during measurement periods; March 15$\sim$April $16^{th}$, 2004 and May 24$\sim$ $8^{th}$ 2005. Extinction coefficient, backscattering coefficient, and lidar ratio were measured at 355 and 532 nm by the Raman method. Different types of aerosol layers were distinguished by the differences in the optical properties such as Angstrom exponent, and lidar ratio. The average value of lidar ratio during two observation periods was found to be $50.85\pm4.88$ sr at 355 nm and $52.43\pm15.15$ sr at 532 nm at 2004 and $57.94\pm10.29$ sr at 355 nm and $82.24\pm15.90$ sr at 532 nm at 2005. We conduct hysplit back-trajectory to know the pathway of airmass during the observation periods. We also calculate lidar ratio of different type of aerosol, urban, maritime, dust, continental aerosols using OPAC (Optical Properties of Aerosols and Clouds), Remote sensing of atmospheric aerosol using a multi-wavelengh lidar system with Raman channels is quite and powerful tool to characterize the optical propertises of troposheric aerosols.

• Journal of the Optical Society of Korea
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• 제15권3호
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• pp.209-215
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• 2011

A new iterative algorithm is developed to estimate LIDAR ratio for a thin cirrus cloud over an aerosol layer. First, the thin cirrus cloud is screened out and replaced by a modeled LIDAR signal and the extinction coefficients of the aerosol layer are derived using the Fernald backward method. These aerosol coefficients are referred as the "actual values". Second, the original LIDAR signal which includes the thin cirrus cloud is also inverted by the Fernald backward method down to the aerosol layer but using different LIDAR ratio for the thin cirrus cloud. Depending on the different assumptions about the LIDAR ratio of the thin cirrus cloud, different sets of aerosol extinction can be derived. The "actual values" which are found in the first step can be used to constrain this iterative progress and the correct LIDAR ratio of the thin cirrus cloud can be found. The detailed description of this method and retrieval examples are given in the paper. The cases compared with other methods are presented and the statistical result is also shown and agrees well with other studies.