Korean Geodetic Datum 2002(KGD2002) : Nationwide GPS Network Densification. Mr. Gwang-Ho Jung, 3) Mr. Sang-Hun Cha. Kyungil University, Rep.

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1 , Stockholm, SWEDEN Korean Geodetic Datum (KGD) : Nationwide GPS Network Densification ) Prof. Young-Jin Lee, ) Dr. Hung-Kyu Lee ) Mr. Gwang-Ho Jung, ) Mr. Sang-Hun Cha ) Kyungil University, Rep. of Korea ) Changwon National University, Rep of Korea ) National Geographical Information Institute(NGII), Rep. of Korea - Contents - Introduction : KGD GPS Observations and Processing Network Adjustment for Densification Concluding Remarks

2 Introduction : KGD Korean Geodetic Datum New Korean horizontal geodetic datum was adopted on st January KGD Aligned to ITRF (Epoch.) Reference Ellipsoid: GRS8 The Published Origin Coordinate of KGD ECEF X -.7 Y.7 Z 88.8 Geographical Latitude Longitude Ellipsoidal height 9.m This datum transition support modern satellite positioning techniques and ensure that spatial data is compatible with international standard!!!!

3 Realization of KGD The realization was achieved by determining the coordinates of its origin and the st order geodetic control points!!! VLBI Observation Joint Geodetic Project of Korean and Japan in 99 CALC & SOLVE S/W was used for data processing to estimate ITRF(epoch 997.) coordinate on November. ITRF(epoch.) coordinate was determined by including the crustal motion vector GPS Observation Coordinate of the origin point was determined by GPS & TS observations in the end of. Coordinates of GPS CORS of NGII was estimated by processing GPS five days GPS observations The CORSs are served as the st order control point in KGD. The nd Order Geodetic Network Points observed by GPS (99-) Baseline length ranges from km to km (Mostly km) Network adjustment was completed in Overall accuracy: cm () & cm () Adjustment Summary Fixed point (D) Number of points Number of unknown parameters Number of observations Degree of freedom Posterior Variance Factor χ Test GPS CORSs 79. Passed

4 The nd Order Geodetic Network Adjusted Network with Absolute Confidence region (Lee et al., & 7) GPS Observations & Processing

5 Objectives To examine the rd Order GPS observations (997-7) To process them to estimate baseline vectors To determine KGD coordinate of the rd Order Points by the baseline vector network Tools GPS PROCESSING S/W LGO & TGO GPS static processing module, BERNESE NETWORK ADJUSTMENT S/W Geolab TM, LGO & TGO network adjustment module The rd Order Geodetic Network The rd order GPS Network () The rd order GPS Network (7) Blank Area will be filled in 8.

6 GPS Observation & Processing GPS rd Order Observations NGII had held GPS campaigns over the rd order geodetic network, from 997 to 7 About, points were observed The campaigns are ongoing to full cover whole country Baseline Processing Processed by surveying contractors who made filed observations (Baseline Length: km - km) Software: Mostly TGO & LGO The solutions were used in subsequent network adjustment unless significant problems exist (e.g, incorrect antenna height and/or reference coordinates) Composition of Networks BLOCK Camps. Points BLOCK Camps. Points 997-L -T,7 998-L -L L 9 UR-L -L -T 8 -L,7 7 -L, -T 9 JJ-L 9 -T T 7 7-,7 -T -T,9, 7-7-SA campaigns,87 Points Networks

7 Network Adjustment for Densification Adjustment Procedures Baseline Vectors & VCV Matrices Mimally Constraned Adjutment of "Campaign Network" Results Acceptable? (Tau Test) Troubleshooting Mimally Constraned Adjutment of " Network" Results Acceptable? (Tau Test) Troubleshooting Empirical Stochatic Modeling Over-Constrained Adjustment (Applying Modified Stochastic Model) 7

8 Minimally Constrained Adjustment The number of the outliers identified from the MC adjustments Name Points outlier Identified Campaign Total Name Points outlier identified Campaign Total 997-L -T L -L L 9 U-L -L -T 8 -L 7 -L -T 9 J-L 9 -T 79 -B 9 -T 7 7-B,7 -T 9 7-B 9 -T 8 7-SA 8 In both of campaign & block network adjustment, a second order point was held fixed. A total of 8 baselines were identified as outliers Minimally Constrained Adjustment Stochastic Modeling (- km) Empirical stochastic modeling scheme was applied (Rizos, 99) Several iterative processing was carried out until the variance factor test (χ ) was passed. Derived magnitude of absolute and relative error Absolute error (a) Relative error (b) mm mm. ppm. ppm After modifying the original VCV matrices, all of the block networks were readjusted by fixing a singe second order control point 8

9 Minimally Constrained Adjustment Summary of coordinate differences of the overlapped points between two adjacent block networks (total points) Component (D) (D) Average.m.m RMS.m.m Summary of differences between the adjusted and predetermined nd points within the block networks (total 7points) order control Component (D) (D) Average.m.8m RMS.m.8m Minimally Constrained Adjustment Statistical summary of relative confidence regions with 9% probability (unit: m) Component Mean Std. Component Mean Std. 997-L.. U-L. 998-L. -T. 999-L. -L. -L.. -L. -L.. -L. -T. J-L. -T.. -block.9.. -T. 7-block.. -T. 7-block..9 -L. 7-SA

10 Over Constrained Adjustment The final stage of the rd order network adjustment Over constrained adjustments were successively performed with respect to the block networks. To be held fixed by; - all available nd order control points within the block network -the rd order control points, overlapped with adjacent networks whose coordinates had been estimated from a proceeding block network adjustment. This approach avoids the repetitious estimation of the overlapped points between two adjacent block networks Over Constrained Adjustment Summary of Over Constrained Adjustments Adjustment Sequence Network Points Baselines Adjustment Sequence Network Points Baselines -T,9, 998-L, -T,7,7 -L,,89 -L 8,8 999-L L,,8 997-L -T 8,7 U-L 87 -T,,97 J-L T 9,9 7 7-,7,8 8 -T 7, ,7 9 -L,9 9 -,8 -T 79, 7-SA 8 7 A total of 7,8 baselines were adjusted to determine the KGD coordinate sets at,87 control points

11 Over Constrained Adjustment Statistical summary of absolute confidence regions with 9% probability (unit: m) Component Mean Std. Component Mean Std. 997-L.. -T L.7.. -L L.7.. U-L.. -L T. -L L.. -T.. J-L T.7.. -block.9.. -T.. 7-block.. -T.. 7-block..9 -T.. 7-SA.8.9. Over Constrained Adjustment An example of adjusted network with absolute confidence region (9%) -L

12 Concluding Remarks Summaries This presentation has described issues related with nationwide GPS network adjustment for the densification of KGD. Details of the rd order GPS network adjustment has been discussed with an emphasis of the network adjustment procedure. Results of the rd order network adjustment showed that overall accuracy of the derived coordinate was evaluated to be about cm and cm in horizontal and vertical component. GPS campaigns are ongoing to cover whole country, simultaneous adjustment is planned to derive final version of KGD coordinate sets.

13 Conclusion Further Works. New GPS Observations in year 8. One-step Adjustment by Integrated network. One-step Updating of Coordinates. Datum Transition Modelling Thank You..