A SPECTRA INS - Integrated Navigation System
and Real-time Binning System

The SPECTRA INS, developed by Concept System Limited, is based on an expandable network of UNIX-workstations or LINUX-PC, providing facilities for acquisition and validation of navigational data, real-time shot positioning, steering display, real-time binning and real-time navigation data quality control.
SPECTRA comprise two main hardware elements, the Real-time Configuration Unit and a series of UNIX workstations or LINUX-PC connected by an Ethernet local area network.

SPECTRA system configurations

An installation on board 2D-3D vessels consists of:
- 3-5 Sun workstations or LINUX-PC running in conjunction with each other to share machine loading;
- 10-20 Gbytes hard disk for real-time data and QC logging;
- Exabyte drive to store raw data files on a safe media after completion of a survey line;
- 3 RTNu, two of them for real time data acquisition and one for spare.

The RTNu is a dedicated multi-microprocessor unit that performs the following tasks:
- Provide time and crude positioning by means of an internal GPS receiver;
- Acquires and verifies data from survey and navigation sensors via a number of serial ports;
- Down-loadable software to allow direct interface to all commercial navigation sensors.  Software can be customized, as required, to accommodate future navigation sensor enhancements;
- Makes time-stamped data available to other processes by sending data over the network to SPECTRA's Data Server;
- Generates output triggers for external equipment;
- Synchronizes external equipment to GPS shot time, both in single and multiple vessel operations.

Each RTNu unit has serial ports installed, and each port allows a separate navigation sensor to be interfaced.
SPECTRA comprise a number of program modules (Nodes) linked together by a common data server running on the primary workstation. Each node performs a set of specified functions that perform particular tasks within the INS system. All nodes can be executed independently of the system that allows, if required, configurations and system checks to be performed externally to the vessel. Each node is controlled by a graphical interface, which reduces the complexity of standard operations and tasks.
The main functions of the software nodes are:

Monitor Node: system control of all program modules. Instigates automatic restart of any aborted module;
Data Server Node: provides central data collection allowing data communications between program modules;
Real-Time Configuration Node: allows the operator to define how information is passed between SPECTRA and the vessel's navigation sensors;
Line Management Node: provides the survey definition parameters and control of data acquisition;
Spread Navigation Node: conforming to UKOOA raw data logging formats; it allows operators to define navigation networks required to calculate positions;
Display Node: multiple alpha-numeric and graphical displays allowing for real-time vessel control and quality control of raw data and network solutions;
Data logging Node: controls the logging of raw data and computed data to hard disk, with off-line transcription to Exabyte tape;
Binning Configuration Node: real-time spatial analysis of CMP locations during data acquisition. Configured as a steering aid it allows operators to control the vessel position for maximum CMP coverage;
Quality Control Node: quality control of all raw data and network solutions. Operators real-time or post-time, producing operator specified EOL reports;
Utility Node: performs various utility operations required to calibrate external navigation sensors.

The data server stores information supplied by the system's producer processes and passes it, on demand, to consumer processes. When producer processes update information, the Data Server keeps the old information as well until there are no consumer processes that need it. All information regarding setup or configuration of a Node can be saved to file, then subsequently reloaded as required. This allows system configurations prior to the contract mobilization.
SPECTRA performs a variety of tasks during normal 2D and 3D to assist the navigators in the operation of the system:

- Logs all raw data arriving at the RTNu as in selected formats;
- Logs user defined QC files. Each file can be configured to monitor all aspects of the network solution from raw data to final positions;
- Alarm windows to indicate actual problems and potential problem;
- Performs a shot by shot quality analysis to highlight areas where contract specifications are not met;
- Produces numerous alpha numeric and graphical displays to show system performance, for example:
1.Helmsman display (steer screens graphical and numerical).
2.Observation residuals.
3.Observation status.
4.Observation age.
5.Observation observed value.
6.Compass biases.
7.Compass headings.
8.Network age.
9.Network degrees of freedom.
10.Spatial analysis.
11.Binning coverage analysis.

Real-time QC analysis of networks for all raw and computed data.

For 3D acquisition SPECTRA incorporates a real-time Binner that comprises a Binning Configuration Node and a binning facility within the Display Node. The real-time Binner provides on-line coverage displays, enabling the optimal course to be steered, allowing for the maximum coverage to be acquired. The Binning Node directly interfaces to REFLEX, Concept System's off-line binning QC system, allowing for the integration of post processed data to the real-time coverage data. This integration of processed data allows navigators to assess the obtained coverage, thus optimizing subsequent line acquisition and selection. The option to view Flexed coverage during real-time acquisition is available, if required.

Reflex off-line binning quality control system

The Reflex off-line binning system has been developed by Concept System Limited to provide 3D binning coverage control facilities combined with more general spatial analysis facilities.
Binning is the technique used to ensure that the fold of coverage obtained on 3D seismic survey is complete. Binning systems are used primarily to assess the number of additional seismic lines that must be shot to infill areas of poor data coverage. This decision is crucial, as too little infill will result in a reduction in the quality of processed seismic data, and too much will increase the cost of the survey. Binning therefore attempts to highlight the gaps in the survey data and to provide an analysis of the required survey area that is as accurate as can be reasonably obtained.
A "bin grid" is defined on the subsurface area for which survey data is required. Survey lines are then shot such that common midpoints fall within the predefined bins. Each cell within the bin grid is known as a "bin" (although in sophisticated system, the bin may not correspond exactly to the original cell; they may overlap, for example).
Reflex is able to show coverage and attribute information based on P1/90 and P2/94 data sets. Both coverage and attribute data can be imported for present or previous data sets.
The Reflex database can contain attributes other than fold. Attributes such as source/receiver azimuth, seismic data quality, and any raw or computed parameters available from Sprint/Spectra and the seismic processing system.
Reflex operates under Solaris on a Sun workstation. Additional external equipment attached to the workstation is as follows:

- External disk is used for storage of all data sets;
- Exabyte for data backup and transfers;
- Twisted Pair Ethernet socket. File transfer between INS and processing system;
- Networked color printer for coverage printouts;

Reflex is built as a number of modules that allow the following tasks to be undertaken:

- Create database capable of holding position and attribute information for all points of interest in any 3D seismic survey;
- Fast access to this data, under a variety of conditions, for presentation purpose;
- Text reports on all setup parameters;
- Graphical time series plots of parameters by line, or line summary against line sequence (time) or line number (area);
- Duplicate offsets rejection;
- Binning data using variety of binning configurations including Tapered binning, Stepped flex, Tapered Stepped flex etc.;
- Re-binning of data should survey parameters change;
- Coverage analysis, including various options to display offsets distribution, coverage statistics and "greater then" or "less than" thresholds;
- Spatial plots analyzing user defined attributes;
- Output of all forms of presentation as full resolution hard copy postscript plots;
- Batch mode import and sampling of lines.