ABSTRAK
Program analisis spektrum telah dibuat dengan menggunakan GUI MATLAB 7 untuk melengkapi program Purnomo yang terdiri dari tiga tahap pengolahan. Tahap pertama meliputi proses gridding data, dan slicing data. Tahap kedua meliputi proses fast fourier transform (FFT), dan windowing. Sedangkan tahap ketiga meliputi proses pemisahan anomali Bouguer ke dalam anomali regional dan residual menggunakan metode inversi, metode polinomial, dan metode moving average. Spasial grid data anomali residual yang dihasilkan program analisis spektrum divariasikan dan dibandingkan dengan anomali residual pada software Oasis Montaj dengan metode pemisahan upward continuation. Berdasarkan hasil perbandingan diperoleh kontur anomali residual spasial grid data 5000 m dengan lebar window 9 paling mendekati kontur anomali residual pada software Oasis Montaj. Lebar window untuk spasial grid data 5000 m kemudian divariasikan pada lebar window 5, 7, 9, 11, dan 13. Proses slicing dilakukan pada kelima kontur anomali residual dengan lebar window 5, 7, 9, 11, dan 13 terhadap kontur anomali pada program pembanding secara berturut-turut menghasilkan korelasi 0.57, 0.68, 0.75, 0.79, dan 0.81. Dengan demikian kontur anomali dengan lebar window 13 memiliki nilai anomali residual yang paling mendekati kontur anomali pada software Oasis Montaj sehingga berdasarkan pendekatan profil kontur anomali, lebar window yang dihasilkan program analisis spektrum belum optimal.
Kata kunci: moving average, fast fourier transform (FFT), window, analisis spektrum.
ABSTRACT
Spectrum analysis program have been made using GUI MATLAB 7 to complete Purnomo’s program consisting of three processing stages. The first stage is gridding data, and slicing data. The second stage covering fast fourier transform (FFT) and windowing. While the third stage, covering regional residual separation process using invers method, polinomial method, and moving average method. Spatial data grid of residual anomaly data produced by spectrum analysis program is varied and compared by residual anomaly at Oasis Montaj software using upward continuation separation method. Based on comparison’s result, it’s obtained the contour of residual anomaly data with spatial data grid 5000 m and the wide window 9 are most closely resembled by contour of residual anomaly by Oasis Montaj software. Wide window to spatial data grid 5000 m is varied on the width of window 5, 7, 9, 11, and 13. Slicing process on the five contours anomaly with the width window 5, 7, 9, 11, and 13 against contour anomaly on the comparison program respectively produce correlation 0.57, 0.68, 0.75, 0.79, and 0.81. Thus, the contour anomaly with wide window 13 has value of residual anomaly approaching the contour anomaly on Oasis Montaj software, so based on an approach contour anomaly profile, wide window produced by spectrum analysis program is not yet optimal.
Keywords : moving average, fast fourier transform (FFT), window, spectrum analysis.