SGNoise and AGDas - tools for processing of superconducting and absolute gravity data Vojtech Pálinkáš and Miloš Vaľko

Transcription

1 SGNose and AGDas - tools for processng of superconductng and absolute gravty data Vojtech Pálnkáš and Mloš Vaľko 1 Research Insttute of Geodesy, Topography and Cartography, Czech Republc

2 SGNose Web tool prmarly orented for SG data qualty control n near real tme Wrtten n PHP5 usng the GD graphcal lbrary Data are processed on daly bass from raw SG data (1 sec samplng rate) Inspred by the prevous works of Rosat et al. (23b, 24, 211, 213), whch establshed a standard feature of the nose spectrum analyss of SGs n the GGP network. The data qualty quantfcaton s represented by the evaluaton of ambent nose level at SG statons by spectral analyss of gravty resduals and ts vsualzaton through spectrograms and probablty densty functons.

3 SGNose - methodology 1 sec data, consstng of gravty and ar pressure sgnal (n ASCII or mseed format) Two basc steps based on Banka and Crossley (1999): computng resdual gravty seres spectral analyss of resduals The ambent nose levels at SG statons are quantfed by Power Spectral Denstes of gravty resduals from.15 mhz (111 mn) up to 61.5 mhz (16 s). Vsualsaton: Spectrograms Probablty densty functons (PDFs usng algorthms gven by McNamara and Buland 24 for sesmc data) Calbraton of gravty data; Subtracton of the tdes usng the observed or synthetc tdal parameters; Reducton for the redstrbuton of atmospherc masses usng local ar pressure data; Subtracton of a best fttng 9 th degree polynomal to elmnate the nstrumental drft and any resdual tdal sgnal. Wndowng wth a Hann wndow; Power Spectral Densty (PSD) estmaton accordng to Cooley and Tukey, (1965); PSD smoothng usng the 11-pont Parzen frequency wndow and ts expresson to decbels relatve to 1 (m/s 2 ) 2 /Hz through 1 log 1 PSD, where PSD s expressed n unts (m/s 2 ) 2 /Hz.

4 SGNose, Vsualzaton

5 SGNose, web page

6 SGNose, Daly outputs

7 Monthly overvew

8 Yearly overvew

9 SGNose, problem detecton

10 SGNose, Comparson

11 AGDAS, objectve Asolute Gravmeter Data Analyss Software wrtten n Matlab Why the AGDAS has been developped? valdaton of the g software accurate defnton of the reference nstrumental heght complex analyss of gravty resduals n spectral and tme doman expermental evaluaton of the questonable correcton from the fnte speed of lght.

12 AGDAS, raw AG data ), cos(2 ) sn (2 ) 24 2 ( ) 6 ( mod mod 4 ' 2 ' 3 ' ' t f b t f a t t g t t v z z c z t t ' t = sec : Tme Dstance pars for at least 7 zero crossngs

13 AGDAS, postonng dt dz v 2 2 g v z z 2 2 g v g g top 2 2 * * * t g t v z z 2 A * A 2 ) ( ) ( g v g g h eff Nebauer et al. (1995) Top of the drop Effectve poston Palnkas et al. (212)

14 AGDAS, effectve heght

15 AGDAS vs. g RefX: Dfference of.3 nm s -2

16 AGDAS, resduals

17 AGDAS, frnge choce Reference soluton Frnges: 3-629

18 AGDAS, spectrum Equally spaced data Non-equally tmed data 1) Interpolaton 2) Least squares spectral analyss

19 AGDAS, experment Correcton due to fnte speed of lght Surprsng theoretcal (Rothletner and Francs 211) and expermental results (Rothletner et al. 214), whch should lead to correct FG5 (and gravty reference too) for 4 Gal. AGDAS s easy to use for detecton f measured g s dependent on the velocty of the test mass

20 Summary and conclusons SGNose s provdng useful nformaton related to the qualty of SG data. Repeated absolute measurements at the staton mght be nmedately compared wth gravty resduals. There s a possblty to extend the nose level analyss to the sub-sesmc and tdal bands. The next work wll be orented for mprovement of automatc data processng. AGDAS s a powerful tool for advanced analyss of AG data as verfcaton of the correcton due to fnte speed of lght. Furher, AGDAS has some advantages wth respect to the g outputs as 1) analyss of resduals for a gven campagn, 2) accurate referencng of the results.

21 Thank you for your attenton!