Positioning Networks In 3D Marine Seismic
Authors: Zinn N.D. , Rapatz P.J.V. 
Published: October 2008

Modern 3-D marine surveys increasingly require multiple geophysical receivers and sources. Complex arrays of navigational sensors am deployed on the vessels and in the water to position these geophysical devices. Clients demand the real-time integration of all observations provided by these sensors into the best possible positions for source centers and cable receivers.

This paper discusses these issues. The concept of a survey network which is central to the processing of heterogeneous observations among a multitude of stations, is clearly defined. This concept is applied to the stations and the observations of a marine seismic network as characterized by Western Geophysical Total NetSM system. A sequential, extended Kalman filter processes the observations of this network Reduced errors at the Horizontal Mid-Point (which determines into which bin a trace will fill) area benefit of an integrated network

1.0 An Introduction to Survey Networks

The term "network" is defined by the National Geodetic Survey (NGS), the government agency responsible for establishing and maintaining geodetic (survey) control in the United States, in the publication Geodetic Glossary. A network is "a set of :stations for which geometric relation have been determined and which are so dated that removal of one station from the set will affect the relationships (distances, directions, coordinates, etc.) between the other stations; andlines connecting the stations to show this interdependence.

The lines represent adjusted distances, directions, or angles or the sequence in which measurements were carried out.

This NGS definition of a survey network identifies two distinct elements:stations (or points or nodes or targets); andlines (or measurements or observations).

This paper adopts the terms "station" and "observation". It is important to distinguish between the graphical representation of a network (points and lines on paper or on a video semen) and the network itself (stations in space with observed measurements of heterogeneous types among them). While the metaphor of plotted points representing actual stations holds up well, the metaphor of lines representing observations fares less well since observations can be of many different types.

1.1 Stations in Land Surveys

A station in a land survey is often a monumented control point (brass cap in concrete) for which coordinates in latitude and longitude, or X and Y, or northing and casting have been determined. A specific station's coordinates are determined by computing (or adjusting) the surveying observations taken among all stations in the network Stations in a land survey may also be church steeples, lights on a microwave tower or a water tank a reference mark in an optical observatory, the center of a radio astronomy antenna and so on.

1.2 Observations in Land Surveys

Observation types in land surveys have grown with advancing technology. These have traditionally been optically observed angles and precisely taped distances. Triangulation is the technique used to provide & station coordinates from (many) angles and (a few) distances.