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MAGNETIC, GRAVITY AND SEISMIC

Magnetics should be performed with the standard procedures that minimize the ship's noise, (i.e. towing the sensor 2-3 times the ship's length). When dealing with single sensor acquisition, the availability of the closest Ground observatory data is necessary for day-night corrections and for rejecting spikes. Furthermore, the data have to be reduced to IGRF anomalies ([13]) or to local anomalies, based upon available Ground Observatories time series). According to sensor's characteristics it may be necessary to check for the magnetic deviation, with lines running at different angles above a common point (preferably in areas with very low gradient and overnight).

Gravimetric surveying dictates the instrumental calibration and drift control by referencing to Control Points as close as possible to the ship. Yet, the data have to be reduced to local anomalies. To check for instrumental drift it is recommended to run crossing lines.

Seismic data can be collected at high speed by using low-noise array configurations. This is a difficult task, however quite important and interesting. The data, whenever possible, should be digitized and recorded in standard formats, such as SEG-D or SEG-Y.


next up previous contents
Next: DATA PROCESSING Up: BATHYMETRIC AND GEOPHYSICAL SURVEYING Previous: SWATH BATHYMETRY   Contents
2001-07-13