1. Geomagnetic Charts of Southern Part of Korean Peninsula as of 2010.0 1 LIM, Mutaek* 1, MOON, Jiyoung 2, PARK, Youngsue 1, SHIN, Younghong 1, RIM, Hyoungrae 1 1 : Korea Institute of Geoscience and Mineral Resources (KIGAM) http://www.kigam.re.kr 2 : National Geography Information Institute (NGII) http://www.ngii.go.kr 22 th Sep. 2010 Presented at 14 th IAGA Workshop at Changchun, China

2. Contents Present status of geomag. meas. in south. part of Korea NGII is to make geomag. charts from measured data Geomag. charts as of 1990.0 from data meas. 1976 - 1996 Geomag. charts as of 2010.0 from data meas. 1998 - 2008 Geomag. charts as of 2010.0 from data newly meas. 2010 Concluding Remarks

3. Beijing Changchun Location of Geomag. Obs. Present status of geomag. meas. in south. part of Korea - 1

4. Present status of geomag. meas. in south. part of Korea - 2 Location of Geomag. Obs. NameInstru. Dur. of Meas. Instit.remarks ZIN (Zinsen = Incheon) 3-axis & scalar 1918 ~ 1944 yearly averaged data exist ICN(Icheon, not yet applied to IAGA) 3-axis & scalar 1996 ~ continual RRLRF521B, geom. noise YON(Yongin, not yet applied to IAGA) 3-axis & scalar 1997 ~ continualRRLRF521B, geom. noise JEJ(Jeju, not yet applied to IAGA) 3-axis & scalar 1997 ~ continual RRL RF521B, geom. noise DZN(Daejeon, not yet applied to IAGA) 3-axis & scalar 1998 ~ continual KIGAMFlare+, geom. noise GZU(Gyeongju, not yet applied to IAGA) 3-axis & scalar 2000 ~ continual KIGAMFlare+, geom. noise HOS(Hongseong, not yet applied to IAGA) 3-axis & scalar 2002 ~ continual KIGAMFlare+, geom. noise CYN(Cheongyang, applied to IAGA ?) 3-axis & scalar 2008 ~ continual KMA MagRec1B, most free from geom. noise Summary of Geom. Obs. in Korea

5. Main & visible purpose for NGII to make geomagnetic charts is the necessity to put the declination on the geographical maps provided to the people. NGII has done absolute geomagnetic measurements on repeat stations and/or on random points: 1976 ~ 1996 : on more than 500 random points including repeat stations, total 902 meas.-pt. 1998 ~ 2008 : on only 30 repeat stations, total 74 meas.-pt. NGII committed to KIGAM to make geomagnetic charts of total magnetic intensity, declination and inclination as of 1990.0 and as of 2010.0 with the data measured by NGII. This can be considered to be an additional work to the main work below. And NGII committed to KIGAM to do absolute geomagnetic measurements on the whole of 30 repeat stations in the year of 2010, to make geomagnetic charts with the newly measured data, and to compare the two sets of charts of the year 2010. 0. The absolute geomagnetic measurements are under doing now. 5 NGII is to make geomag. charts from measured data

6. Assuming that local distribution of geomagnetic features(tot. mag. intens., dec., inc.) vary very smoothly, and therefore Considering IGRF as exemplary, many outlying data from the IGRF were eliminated. The greatest deficiency of the data set being the non-existence of the measurement date and time records, we have imagined that each measurement has been done in the middle of the year. So, there would be considerable errors on geomagnetic features(tot. mag. intens., dec., inc.), especially more on declination than on inclination. 6 Geomag. charts as of 1990.0 from data meas. 1976 – 1996 - 1

7. 7 Geomag. charts as of 1990.0 from data meas. 1976 – 1996 - 2 Original data distribution : 902 meas.-pt. Reduced data distribution : 773 meas.-pt. Reduced data distribution : 677 meas.-pt. Finally reduced data distribution : 593meas.-pt. Final constraints applied to eliminate the meas.-pt. thought to have considerable deficiency : if abs(tot. mag. intens. – IGRF11) > 500 nT or if abs(dec. – IGRF11) > 0.5 deg or if abs(inc. – IGRF11) > 0.5 deg

8. Geomag. charts as of 1990.0 from data meas. 1976 – 1996 - 3 Original data distribution of difference of each feature – IGRF11 Finally reduced data distribution of difference of each feature – IGRF11 Constraints applied

9. Geomag. charts as of 1990.0 from data meas. 1976 – 1996 - 4 Final geomagnetic charts as of 1990.0 in comparison with the IGRF11

10. Also assuming that local distribution of geomagnetic features(tot. mag. intens., dec., inc.) vary very smoothly, and therefore Considering IGRF as exemplary, several outlying data from the IGRF were eliminated. The considerable deficiency of the data set being the non-existence of the measurement time records, we have imagined that each measurement has been done in the middle of the day. So, there would be some errors on geomagnetic features(tot. mag. intens., dec., inc.), especially more on declination than on inclination. 10 Geomag. charts as of 2010.0 from data meas. 1998 – 2008 - 1

11. 11 Geomag. charts as of 2010.0 from data meas. 1998 – 2008 - 2 : measured values for rep. stn. No. 1, - : values calculated from IGRF11

12. 12 Geomag. charts as of 2010.0 from data meas. 1998 – 2008 - 3 Original data distribution : 74 meas.-pt. Finally reduced data distribution : 72 meas.-pt. Final constraints applied to eliminate the meas.-pt. thought to have considerable deficiency : if abs(tot. mag. intens. – IGRF11) > 500 nT or if abs(dec. – IGRF11) > 0.5 deg or if abs(inc. – IGRF11) > 0.5 deg

13. Geomag. charts as of 2010.0 from data meas. 1998 – 2008 - 4 Original data distribution of difference of each feature – IGRF11 Finally reduced data distribution of difference of each feature – IGRF11 Constraints applied

14. Geomag. charts as of 2010.0 from data meas. 1998 – 2008 - 5 Final geomagnetic charts as of 2010.0 in comparison with the IGRF11

15. To ameliorate the quality of geomagnetic charts to be made from newly measured data in 2010, we will add 3 works as follows; 1. to get site difference between each rep. stn. and geomagnetic observatories 2. to do magnetic survey to certify that each rep. stn. is at a place without any magnetic anomaly 3. to do at least 5 sessions of absolute geomagnetic measurements to get a believable baselines 15 Geomag. charts as of 2010.0 from data newly meas. 2010 - 1

16. 16 Geomag. charts as of 2010.0 from data newly meas. 2010 - 2 Set up of a magnetometer Derived difference -754.5 nT from Blue : CYN Geomagnetic Obs. Red : GZU Geomagnetic Obs. to get site difference between each rep. stn. and geomagnetic observatories

17. 17 Geomag. charts as of 2010.0 from data newly meas. 2010 - 3 Magnetic survey Magnetic survey result on rep. stn. no. 22 Left : total mag. Intens. (nT) Right : gradient (nT/m) to do magnetic survey to certify that each rep. stn. is at a place without any magnetic anomaly

18. 18 Geomag. charts as of 2010.0 from data newly meas. 2010 - 4 excel file of 1 measurement to do at least 5 sessions of absolute geomagnetic measurements to get a believable baselines Date2010-09-08-1 Observer 임무택 Code 1-22-3- 경주 Mark Up2092322209.3894 F site Diff0.0 Mark Down29233029.3917 Mark Up2092324209.3900 Mark Down29232529.3903 Mean1192325119.3903 FM True116235116.0431 TN Circle320503.3473 Time Flare D ED16:38:123553859355.6497-388.9 WD16:40:471753344175.5622-388.5 EU16:45:111753831175.6419-387.8 WU16:49:233553740355.6278-387.1 Mean16:43:232653713265.6204-388.1 Declination (Absolute) -74337-7.7269 Time Flare HFlare ZFlare F SU17:14:50128274751.536925.51295.750173.8 ND17:17:09308295451.501725.31295.650173.7 SD17:05:11231324551.545825.91295.450174.0 NU17:07:3851304151.511425.61295.550173.7 Mean17:11:1251312651.524025.61295.650173.8 Inclination (Absolute) 513126 Corrected50173.8 FlareAbsoluteBaseline H25.631217.531192.0 D-0.7122-7.7269-7.0146-3809.2557-7052 Z1295.639279.537983.9 ^ Dec. of Baseline Collimation 시준 ( 오차 ?) Dec. δ-0.014 Dec. ε-0.015 Dec. Zo13.8 Inc. ε-0.005 Inc. Zo15.3

19. 19 Geomag. charts as of 2010.0 from data newly meas. 2010 - 4 Summary of 6 measurements with baselines calculated Quality? to do at least 5 sessions of absolute geomagnetic measurements to get a believable baselines ListDeclinationInclinationCorrected TotalHbaseDbaseZbase 2010-09-08-1-7.726951.524050173.833331191.97-3809.255737983.93 2010-09-09-2-7.774551.585550141.200031155.99-3827.367638004.86 2010-09-09-3-7.817851.544550141.100031183.58-3827.909837982.78 2010-09-09-4-7.447651.664950148.433331101.57-3613.829038049.50 2010-09-09-5-7.811051.575350156.033331160.57-3817.668638004.58 2010-09-09-6-7.796751.534950159.166731187.10-3815.867637984.32

20. Concluding remarks Geomag. charts as of 1990.0 were made from data meas. 1976 – 1996 by eliminating considerable no. of original meas.-pt. Geomag. charts as of 2010.0 were also made from data meas. 1998 – 2008 by eliminating a little of original meas.-pt. Geomag. charts as of 2010.0 with an ameliorated quality will be made from data newly meas. 2010 by applying all generally used methods. We will do everything to get a more reasonable result than the olders. Thank you for your attention!