MAGNETIC GRADIOMETER SURVEY AT W. P. LABUAN, MALAYSIA

The new layout of gases pipe line in W. P. Labuan requires detailed mapping of existing gases pipe line in order to prevent the collisions. Conventional methods rely on ground penetrating radar (GPR) survey, but can lead to significant errors in estimating anomalous body locality if the surveyed area contain with clay such as shoreline environs. An improved approach is to enhance the anomalies produced by shallow buried objects from proxy measurements of magnetic Gradiometer. Magnetic gradient measurements are made by a gradiometer, which are simply two magnetic sensors separated by a constant offset. By using this technique, the measurements are relatively easy to make, it does not require intrusive ground contact, and portable. Measurements from 109 magnetic stations collected within the 11 survey line (line grid arrangement) show the significant of the shallow magnetic anomalies regarding to the inspected pipe line. Magnetic contour maps calculated from magnetic survey data (an extrapolation data) show a related anomaly pattern for each lines correspondence with anomalous body. Data processing includes the diurnal removal by using base station rapid measurements, linear convolution filter (low-pass filters) for noise removal, linear regional anomaly separation and half-width rules for anomalous body depth estimations. Theoretically, the gradiometer measurement are less sensitive to deeper objects than total field measurements, therefore the magnetic measurements are susceptible to interference from buried pipe line. By using anomaly amplitudes, horizontal pipes have a half width rule in near vertical magnetic fields of Z = 2X1/2. The value of half the X distance at half the amplitude is a rule of thumb that is handy for estimating the depth from the shape of observed anomaly. From the anomaly pattern, it was assumed that the anomalous body is a dipole manner. As a result, the simple 2-D and 3-D view of the pipe line is illustrated in this paper. In addition, the comparison between different survey traverse (pole directions) due to anomalous body explain in this paper.