• Korean Journal of Remote Sensing
• /
• v.28 no.2
• /
• pp.191-202
• /
• 2012

A high resolution satellite imagery such as KOMPSAT-2 includes a material containing rational polynomial coefficient (RPC) for three-dimensional geopositioning. However, image geometries which are calculated from the RPC must have inevitable systematic errors. Thus, it is necessary to correct systematic errors of the RPC using several ground control points (GCPs). In this paper, we propose an efficient method for automatic correction of image geometries using tie points of a stereo pair and the Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM) without GCPs. This method includes four steps: 1) tie points extraction, 2) determination of the ground coordinates of the tie points, 3) refinement of the ground coordinates using SRTM DEM, and 4) RPC adjustment model parameter estimation. We validates the performance of the proposed method using KOMPSAT-2 stereo pair. The root mean square errors (RMSE) achieved from check points (CPs) were about 3.55 m, 9.70 m and 3.58 m in X, Y;and Z directions. This means that we can automatically correct the systematic error of RPC using SRTM DEM.

• Journal of the Korean GEO-environmental Society
• /
• v.21 no.6
• /
• pp.13-17
• /
• 2020

In the era of the fourth industrial revolution, drones are being used in various civil engineering fields. Currently, the construction and maintenance of slopes are generally managed by manpower. This method has a risk of safety accidents, and it is difficult to accurately evaluate the slope because it is difficult to secure the vision. In this paper, the effects of RTK and GCP on the 3D model of the slope were studied by using digital images taken by the drone. GNSS coordinates were measured for nine points to compare the quality of the slope 3D model, three points of which were used as the check points and the remaining points were used as GCPs. When making the 3D model of the slope using high-accuracy geotagging images using RTK, it was found that the error at the check point decreases as the number of GCP increases. Even if GNSS was used, it was found that the error at the check points of the 3D slope model was not significant when the GCPs were applied. However, it was found that even if high-accuracy geotagging images are used using the RTK module, a significant error occur when the 3D slope model is created without applying GCPs. Therefore, it can be stated that GCP must be applied to create the 3D slope model in which information about the height as well as plane information is important.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.32 no.4_1
• /
• pp.299-309
• /
• 2014

This paper evaluated the possibility for 1/5,000 digital topographic mapping by using PLEIADES images of 0.5m GSD(Ground Sampling Distance) resolution that has recently launched. Those results of check points by applying the initial RPC(Rational Polynomial Coefficient) of PLEIADES images came out as; RMSE of those were $X={\pm}1.806m$, $Y={\pm}2.132m$, $Z={\pm}1.973m$. Also, if we corrected geometric correction using 16 GCP(Ground Control Point)s, the results of RMSE became $X={\pm}0.104m$, $Y={\pm}0.171m$, $Z={\pm}0.036m$, and t he RMSE of check points were $X={\pm}0.357m$, $Y={\pm}0.239m$, $Z={\pm}0.188m$; which of those results indicated the accuracy of standard adjustment complied in error tolerances of the 1/5,000 scale. Additionally, we converted coordinates of points, obtained by TerraSAR. for comparing with measurements from GPS(Global Positioning System) surveying. The RMSE of comparing converted and GPS points were $X={\pm}0.818m$, $Y={\pm}0.200m$, $Z={\pm}0.265m$, which confirmed the possibility for 1/5,000 digital topographic mapping with PLEIADES images and GCPs. As method of obtaining GCPs in unaccessible area, however, the outcome evaluation of GCPs extracted from TerraSAR images was not acceptable for 1/5,000 digital topographic mapping. Therefore, we considered that further researches are needed on applicability of GCPs extracted from TerraSAR images for future alternative method.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.36 no.6
• /
• pp.565-572
• /
• 2018

Recently, UAVs (Unmanned Aerial Vehicles) or drones have gained popularity for the engineering surveying and mapping because they enable the rapid data acquisition and processing as well as their operation cost is low. The applicable fields become much wider including the topographic monitoring, agriculture, and forestry. It is reported that the high geospatial accuracy is achievable with the drone photogrammetry for many applications. However most studies reported the best achievable mapping results using well-distributed ground control points though some studies investigated the impact of control points on the accuracy. In this study, we focused on the drone mapping of corridors such as roads and pipelines. The distribution and the number of control points along the corridor were diversified for the accuracy assessment. In addition, the effects of the camera self-calibration and the number of the image strips were also studied. The experimental results showed that the biased distribution of ground control points has more negative impact on the accuracy compared to the density of points. The prior camera calibration was favored than the on-the-fly self-calibration that may produce poor positional accuracy for the case of less or biased control points. In addition, increasing the number of strips along the corridor was not helpful to increase the positional accuracy.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
• /
• 2002.04a
• /
• pp.187-194
• /
• 2002

본 논문에서는 SPOT 입체영상을 이용하여 광범위한 지역의 DEM을 제작할 경우 DEM 모자이크 과정에서 발생할 수 있는 접합선(seam-line)을 최소화할 수 있는 방법을 연구하였다. 지상의 60km$\times$60km 영역을 촬영할 수 있는 SPOT 위성의 입체 영상으로부터 구성한 단일 모델은 일반적으로 관심 있는 지역의 DEM을 제작하기에 충분히 넓은 지역을 포함할 수 있다. 그러나 광범위한 지역의 DEM 제작을 위해서는, 각각의 입체영상을 통해 제작된 DEM들을 접합해야 하며, 이 때 발생되는 접합선을 효과적으로 제거하는 작업이 필요하다. 이를 위해 SPOT 위성영상의 블록 조정 방법을 이용하여 종횡접합모델을 구성하고 중복되는 인접한 SPOT DEM간의 표고값을 일치시키므로써 DEM 접합선의 발생을 최소화하여 모자이크시 작업량을 줄이고자 한다. 본 논문에서는 기존의 지상기준점과 추가로 관측한 영상접합점을 이용하여 종횡접합 블록을 구성하고 광속조정 방법을 적용하여 블록에 포함된 위성영상의 외부표정요소를 계산하였다. 블록모델을 이용하여 DEM을 제작할 경우 접합선 탐색 및 blending 작업 없이 단순중첩 방법으로도 DEM 모자이크 작업을 빠르게 수행할 수 있음을 확인하였다.

• The Journal of the Korea Contents Association
• /
• v.13 no.10
• /
• pp.574-583
• /
• 2013

The coastal area, which is managed by local governments, geographically, culturally and economically has been transformed into more influential space. In recent years, new type of fusion researches about coastal areas that have economic, cultural and engineering aspects, have been conducted. In this study, the multiple observations information was used to analyze change of Ilsan beach shoreline which is located in Dong-gu, Ulsan, Korea. For the shoreline analysis, we used VRS-RTK(Virtual Reference System by Real-Time Kinematic) GPS survey, aerial photograph, terrestrial LiDAR survey and fixed reference station survey. Specially fixed reference station method was suggested for shoreline observation and maintenance. In the case of Ilsan beach shoreline, according to the result of multiple observations information, coastline erosion(6~12m) appeared in medium and lower part and sedimentation(3~14m) in the upper part of coastline.

• Spatial Information Research
• /
• v.13 no.1 s.32
• /
• pp.55-63
• /
• 2005

Direct Georeferencing(DG) Is based on the direct measurement of the projection centers and rotation angle of sensor through loading the GPS and INS in aircraft. The methods can offer us to acquire the exterior orientation parameters with only minimum GCPs, even the ground control process could be completely skipped. Hence, as long as securing Digital Elevation Model (DEM), it is feasible to generate digital orthophotos without performing the aerial triangulation with Ground Control Point (GCP) surveying. In this study, the DEM is automatically generated by using a image matching technique based on aerial photos and exterior orientation parameters. This is followed by producing an orthophoto from these results. Finally, accuracy analysis of the georeferencing technique for generating orthoimage indicates that RMS errors of 62cm and 76cm occurred at the X and the Y axis, respectively. This means that the results fulfill the demanding accuracy of the 1:5000 digital map. Hence, it is possible to conclude from this study that the direct georeferencing based orthoimage generation method is able to effectively digital map update.

• Proceedings of the KSRS Conference
• /
• 2001.03a
• /
• pp.140-148
• /
• 2001

The satellite sensor model is typically established using ground control points acquired by ground survey Of existing topographic maps. In some cases where the targeted area can't be accessed and the topographic maps are not available, it is difficult to obtain ground control points so that geospatial information could not be obtained from satellite image. The paper presents several satellite sensor models and satellite image decomposition methods for non-accessible area where ground control points can hardly acquired in conventional ways. First, 10 different satellite sensor models, which were extended from collinearity condition equations, were developed and then the behavior of each sensor model was investigated. Secondly, satellite images were decomposed and also pseudo images were generated. The satellite sensor model extended from collinearity equations was represented by the six exterior orientation parameters in 1$^{st}$, 2$^{nd}$ and 3$^{rd}$ order function of satellite image row. Among them, the rotational angle parameters such as $\omega$(omega) and $\phi$(phi) correlated highly with positional parameters could be assigned to constant values. For non-accessible area, satellite images were decomposed, which means that two consecutive images were combined as one image. The combined image consists of one satellite image with ground control points and the other without ground control points. In addition, a pseudo image which is an imaginary image, was prepared from one satellite image with ground control points and the other without ground control points. In other words, the pseudo image is an arbitrary image bridging two consecutive images. For the experiments, SPOT satellite images exposed to the similar area in different pass were used. Conclusively, it was found that 10 different satellite sensor models and 5 different decomposed methods delivered different levels of accuracy. Among them, the satellite camera model with 1$^{st}$ order function of image row for positional orientation parameters and rotational angle parameter of kappa, and constant rotational angle parameter omega and phi provided the best 60m maximum error at check point with pseudo images arrangement.

• Journal of Korean Society for Geospatial Information Science
• /
• v.14 no.4 s.38
• /
• pp.11-18
• /
• 2006

In this paper, airborne LiDAR data were evaluated in horizontal and vertical accuracy. By using zigzag scanning type of LiDAR, GCPs are not tested directly. So points around GCPs were used in this evaluation. Building corner points were made from LiDAR's building planar and compared with ground surveyed GCPs, in horizontal accuracy test. Its accuracy shows 19cm average and 21cm RMSE and 15 points were within 20cm among 16 points. In vertical accuracy test, 41 GCPs were used and it shows 11cm average and 14cm RMSE and 75% of GCPs were within 15cm. This could be a criterion in topographic map modification and basic geographic DB and 3D data construction using airborne LiDAR data.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.37 no.2
• /
• pp.445-449
• /
• 2017

Most studies using drone is confined utilization on the ground and regulation. The drone in the water is rarely used in hydrographic surveying because of the limit of flight time and image matching. This paper is the basic research for drone hydrographic photogrammetry. The accuracy of hydrographic photogrammetry, using buoys for water reference point, was evaluated. The accuracy is influenced by the accuracy of the water reference points like the photogrammetry. The position of water reference points set up on water, keep on changing due to various environmental factors such as wind speed and water velocity. The position continuously changed of the water reference points were measured 3 times using Total Station and VRS. Experiments were conducted at two reservoirs in Gimhae City, and the accuracy of the manual image matching using the water reference points is 40 cm and 80 cm. Allowable accuracy of the ocean boundary survey is ${\pm}2m$, the results of this study are fully available. The maximum position error of the water reference point for ensuring accuracy within ${\pm}2m$ is 1.8 m.