GDS-II^®

GDS-I^®, GDS-I Plus^®, GDS-II^® (Geophysical Digital System) are modern universal vibrator control systems that come complete with a radio communication subsystem and integrated GPS/GLONASS receivers.

To know more about innovations in GDS-II^® You can download our brochure.

The vibrator control system consists of universal devices each of which is able to work in two modes:

• Encoder — radio communication between the seismic recording system and the vibrators;
• Decoder — the vibrator control.

The ENCODER mode

The main functions in the Encoder mode:

• Controlling groups of vibrators.
• Setting sweep parameters and various operating modes of vibrators.
• Synchronizing with the seismic recording system:

  • standard interface: REF, START, TIME_BREAK;
  • Sercel: Open VibCtrlInterface;
  • ION (Input/Output): RTI interface.
• Receiving, decoding and processing information on quality control of vibrator operation: PSS, Radio Similarities and GPS data.
• Receiving ready signals, automatic launch of the seismic recording station at the Ready signal of a group of vibrators with the REMOTE_START signal.
• Transmitting differential GPS corrections to vibrators in the «Single Radio» mode.
• The Sequences mode.

The DECODER mode

The device controls a seismic vibrator.

The main functions in the Decoder mode:

• Calibration — automatic adjustment to vibrator parameters of different manufacturers.
• Receiving information from the Encoder over the radio: setting parameters, starting vibrators.
• Regulating Force and Phase while sweep generating.
• Controlling quality of vibrator work (Force, Phase, Distortion) at every impact, transmitting these data to the Seismic Station over the radio.
• Recording of the main vibrator signals to USB Flash Drive. The records can be used for HFVS processing  (the ExxonMobil Corporation patent) as well as for troubleshooting of the vibrator sensors and cables.
  The following signals can be recorded:
  • Reference, Acceleration
  • Mass and Valve positions, Torque Motor current
  • GPS data

Quality control

1. After the execution of a sweep, vibrators transmit information about the quality of PSS  (Post Sweep Service). This information includes graphic and tabular data.
2. The quality of vibrators work can be checked through the radio channel. Phase deviations, ground force and emerging distortions are checked.
3. The information about peak and average phase values, force and distortions is shown on the display in real time. The information about the achieved limits on torque motor current, on reaction mass and valve shift, on reaching the peak force is displayed in real time as well.

The force-time relation is shown in percent.

Vibrators group management sequence:

1. Setting the parameters of the sweep-signal and vibrators
2. Transmitting source point coordinates to the vibrators
3. Receiving and saving all PSS
4. Receiving and saving all vibrator similarity tests
5. Transmitting a PSS message to the seismic recording system (quality of vibrator work and topographic data)
6. Seismic data receiving from the seismic recording system (networking), gain-frequency characteristic analysis and sweep parameters transmitting to ENCODER  (adaptive vibroseis).

To support thease objectives GDS-II^® is equiped with modern radio and navigation devices.

Radio Net

The control system uses the following radio devices:

A general-purpose radio modem connected to voice UHF radio.

Radio modems provide radio net between the Encoder and Decoders through Radio.
Three types of data transmitting are supported::

1. Digital transmission, for exchanging parameters, starting the vibrator.
2. Digital transmission at the controlled speed for transmitting PSS.
3. Analog transmission used for the Similarities signal.

The control system allows working in poor radio signal conditions (signal/noise 10 – 20 dB depending on the transmission speed). The radio transmitted PSS data are at the same time recorded to the Decoder NVRAM and can be read later over the radio or cable.

Local Net — for interaction of the vibrators within the group.

Local Net is based on the built-in transceivers of the license-free range of 433-434 MHz.
Local Net provides:

1. Forming of the READY signal of the vibrator group. The signal is formed after the base plates of all vibrators in the group are lowered.
2. Calculating of the gravity center of the vibrator group when moving.
3. Sending differential GPS corrections from the master vibrator to the slave ones.

Vibrators from different groups can use various frequency subranges

Navigation

The control system can use built-in GPS/GLONASS receivers  (JAVAD JNS 100-GG) or any other external ones working under the NMEA protocol.
In the DGPS mode, correction transmission is provided through:

1. the encoder’s main radio modem immediately after the start command (the Single Radio mode)
2. the encoder’s complementary radio modem
3. the assigned base station; in this case, it is necessary to install a special radio modem (Spektr-48 MSK OEM) to the decoder

When the vibrator is moving, the name of the nearest source point (SP), the distance from the SP to the vibrator, and the distance from the vibrator to the nearest center of gravity are shown on the display.

GDS-II^® can set a sweep using a spectrum.

In order to do it, in the Sweep Spectrum window, you must fix/determine desired levels for 16 frequencies in the service band.

After setting the spectrum, no preparation is required, the system is ready to carry out the start of vibrators and there is no need for transmitting the Sweep Table.

The control system can use satellite navigation for the following tasks:

1. Installation of group vibrators to surface position with the help of Tablet computer installed in the cabin.
2. The calculation of COG (Center Of Gravity) by the group of vibrators with the indication of distance from COG to the nearest surface position to the vibrator’s operator.
3. Transfer of navigation information to the seismic station by radio for operator’s control and use in the processing of seismic data.

GDS-II^® can use the built-in GPS/GLONASS receivers (JAVAD TR-G2, TR-G3) or any external ones working under the NMEA protocol.

For the DGPS mode our equipment can independently transmit differential corrections from the GPS Base Station to the vibrator by the following ways:

1. The radio station of recording system after a start command sweep (Single Radio mode). The GPS Base Station must be installed on the vehicle of recording system.
2. The separately base station. In this case, differential corrections may be accepted by a vibrator in the group or be an individual one. After the leading vibrator has received these corrections it starts transferring them to others vibrators in the group by a Local Net.

The base station is a equipment including a GPS receiver, voice radio station and radio modem. It can be installed in any place with the the battery-powered 12 volt. All control units have additional built-in radio modems to receive differential corrections.

Files in SEG-P1 and SPS formats are used to download source point to the control program unit coordinate.

The control program automatically recalculates coordinates obtained from the GPS receiver at any given datum, particularly in SK-42.

At the end of the work on the seismic profile the operator can generate a report which contains the coordinates of the vibrators group center. The report can be saved to the file and used in the further seismic data processing.

The important stage of seismic surveys is to assess the quality of the vibrator. There are various gauges, but the task is complicated by the fact that the behavior of the vibrator is largely determined by the parameters of the soil. That is why, to assess the quality and condition of the vibrator on the one or two points is often very difficult and sometimes impossible task. The situation is further aggravated by the fact that the soil is constantly changing its properties during the measurement.

A statistic processing of the data for a large number of source point (SP) gives more reliable assessment of vibrators.

GDS-II^® system allows making a report on the PSS in a specified range of source point. The report will display the average values of the main parameters of vibrators. In addition the table with the surface position numbers will be created where the vibrator specifications do not meet the acceptable values.