Ranger 2 allows for multiple subsea targets to be tracked simultaneously from a surface vessel. To allow pre-plotted lines to be run and the active transponder list to be automatically updated without operator intervention, Ranger 2 is interfaced to a dedicated survey management application called HydroPos USBL V2.
Fitted in the vessel instrument room, the Ranger 2 and HydroPos software runs on a Navigation Computer connected to a Navigation Sensor Hub (NSH). The NSH provides the interface between the computer and the subsea transponders via the vessel-mounted HPT transceiver.
The software is easy and intuitive to use, requiring only basic operator training to become familiar with it. Ranger 2 includes an extensive array of tools to allow the user to assess the performance of the system, including real-time acoustic quality indicators, noise analysis and signal travel time displays.
Acoustic positioning operations can be monitored over a vessel network using either HydroPos USBL or Viewpoint which offers the added the functionality of supporting .dwg format backgrounds and geodesy.
HPT is a high performance, vessel-mounted acoustic transceiver that enables the targets being tracked with Ranger 2 to be precisely positioned. The HPT transceiver is also used as a modem with Sonardyne’s acoustic modem and subsea data collection transponders thereby allowing the transfer of short QC data messages between each seismic node and the vessel.
The deployment method of the HPT transceiver is critical to Ranger 2’s positioning and modem performance. It should ideally be rigidly mounted to the vessel well below the keel away from any weather or vessel induced aeration. Sonardyne’s hydraulic through-hull deployment systems are extremely rigid and ideal for permanent vessel installation, whether new-build or retro-fit. For short-term projects on vessels-of-opportunity, a high quality over-the-side deployment system is available that is practical to transport and install on a vessel whilst it is alongside.
ROV and Basket Transponder
Ranger 2 is compatible with a wide range of Sonardyne 6G and previous generation subsea transponders. For ROV operations the small, lightweight Wideband Mini Transponder 6 (WMT 6) is recommended. It is depth rated up to 3,000 metres and can operate as either a transponder or as a responder which offers faster position updates.
HydroPos USBL V2 Software
Survey data can be imported into HydroPos USBL from client supplied OGP P1 pre-plot files, CSV files or entered by the user directly. Final survey coordinates for the deployed and as-pinged nodes can be similarly exported in OGP P1 or CSV format. The raw survey data can also be exported as a OGP P2 file as well as a variety of other proprietary formats supported by many of the independent QC packages.
HydroPos USBL is configured around a graphical screen, providing the user with a clear visual display of the data acquisition process, whilst all raw and processed data is stored in a single log file to allow for easy archiving of the data.
Subsea Inertial Navigation
The addition of Sonardyne’s SPRINT technology allows full integration of Sonardyne’s 6G acoustics with a dedicated subsea inertial navigation sensor. SPRINT allows for the final position of the node to be fixed quicker than solely acoustics, thereby operational time on each node deployment.
Nodal Acoustic Telemetry
Sonardyne’s nodal acoustic telemetry technology allows for the transfer of a short QC status record from each 4C seismic node back to a master vessel, regardless of the position of the master vessel within the survey area. The data uploaded contains information such as the recording status of the node, along with parameters such as remaining data capacity and battery capacity. This data can be tailored to clients’ requirements but will always contain a unique node identifier. The node status record is transmitted via a small unit attached to the side of the node. Acoustic Micro modems have been designed to have minimal impact on the handling of the node, both onboard the vessel and subsea. Depth rated versions up to 3,000 metres are available, allowing for all known current nodal operations. The node status record is received in the water column by a network of subsea data collection transponders deployed across the nodal network. Anchored to the seabed on long strops and supported by subsea flotation devices, the transponders are typically deployed by ROV to ensure complete acoustic coverage of a specific section of the seabed network. This also ensures a transponder is not inadvertently placed directly on top of a node. Each transponder uses Sonardyne’s Wideband 2 signal technology to then transmit the status data packet from each node across the seabed network, acoustically ‘hopping’ from unit to unit until it is received by the transponder that is closest to the surface vessel. Data is then uploaded to the vessel-mounted HPT installed on the survey vessel for analysis. Once the survey is complete, the precision offered by Ranger 2 ensures that the ROV can navigate directly to each node to recover it. This ensures no nodes are left behind on the seabed. The transponders can be efficiently recovered by acoustically commanding them to release their anchor weights so that they float up to the surface.