| 摘要 |
A method of making for an area a map or a representation of regional variations in the position of the geoid which have an amplitude less than about 1 m. and are caused by density variations in the underlying sea floor. The map or representation is intended primarily for use in the determination of part areas of the sea floor with increased probability of deposits of natural resources, the density of which part areas distinguishes from that of the surroundings. The method comprises (a) obtaining height values which indicate the sea surface height in relation to reference level and which have been calculated by means of altimeter data measured from a flying craft and by means of information about the orbits of the flying craft during measurement of the altimeter data; (b) sorting out incorrect and improbable values; and (c) adapting the height values corresponding to different orbits of the flying craft to one another, such that maximum agreement of height values is obtained in the crossing points of the orbits, whereby relative values of the geoid position are established. The method is characterised by (d) filtering off long-wave variations with a wave length exceeding about 200 km in the geoid position; (e) amplifying variations in the geoid position which have a selected spread; and (f) correcting the geoid position in respect of interference from the water depth.
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