The Sea Bed Survey

The survey is accomplished through the use of good survey/mapping practice and a custom data collection system. A detailed site survey can be very time consuming so we have integrated a system of sonar technology and processes that automate much of the data collection. To survey a site quickly and accurately we are making extensive use of DGPS technology to carry out all the positional tasks of the survey. Associate Tony Piepjohn of Coast Spatial GIS & Mapping Specialists has been using GPS technology in resource surveying since 1994 for many different purposes and clients. All GPS related work is carried out to the BC Resource Inventory Committee (RIC) standards for GPS surveys. RIC standards are what all provincial agencies use to ensure any GPS related work is carried out with suitable methods and equipment. Mr. Piepjohn has the RIC certification Level 4 (good for all aspects of GPS from field work, processing, mapping, and survey design) and can ensure GPS activities are being carried out properly.

Equipment

The DGPS receiver used for the bathymetric survey is a Trimble Pro XRB. The receiver is a high-end survey and GIS mapping unit that we use in real-time correction mode using the Canadian Coast Guard (CCG) beacon in Richmond BC (320 kHz). The horizontal accuracy achieved from this unit using the CCG service is better than 5 meters 95% of the time on the water. The system has been validated against precisely known control monuments and has achieved +/- 40 cm in one case and +/- 1.3 m in another. The situation over water is ideal for using GPS as there is no screen effect from tree canopy or reflection from surfaces above the antennae, such as close rock bluffs or buildings. The productive power of a high-end GPS receiver lies in our ability to interface the receiver with a high-end sonar unit.

The sonar used is a high-end custom Lowrance X15 with an 8E cone angle for better deep-water penetration down to 1300 feet in salt water. The custom transducer is fitted to a device, mounted to the survey vessel, which also houses the DGPS antennae so that both the transducer and DGPS antennae are in the same vertical positions. This eliminates the need to compensate readings when the two are a few meters apart. The resulting data are very Aclean@ meaning that there is very little noise or unexpected positions.

SEAEYE Falcon ROV can be used for underwater surveys, inspections, search and recovery. It is easily deployed and recovered by hand and has a powerful 1:1 thrust to weight ratio for the best performance of any ROV in it's class. Please follow link to www.suboceanic.net for more details.

Data

Just as important as collecting good data is knowing how to deal with bad data. We identify bad data in a number of ways. Sonar is subject to much more Anoise@ than the GPS data so it must be filtered carefully. During tight turns the system is paused or the data is filtered afterward as cavitations underneath the transducer results in suspect data. As well, very rapid elevation changes or fish schools can overwhelm the processing capabilities of the sonar in which case the sonar may transmit no data at all.
Through software and wiring customization we are able to associate sonar readings to GPS positions automatically and thus have a tool for collecting large volumes or bathymetric data tied to accurate surface positions.
For the site survey, the sonar sends many depth samples per second, but we have used the GPS software to limit recording depth samples to one sample every two seconds. With boat speed of 1 - 2.5 meters/second this yields a maximum distance of 4 to 5 meters between soundings. The transects are generally 15 meters apart within the actual lease boundary and 30 meters apart outside the boundary to the maximum likely extent of the anchor system. This transect type pattern results in a grid pattern survey where we use the navigation potential of real-time DGPS to keep on a line of position (LOP) for each transect.
The main factors influencing the area required for the anchor system is depth of the sea and slope of the sea bottom. A deeper and steeper site requires a more extensive survey so this efficient, productive, and accurate method becomes more crucial to a successful survey and adequate installation. GPS is also used to locate and verify the shore details such as lease markings/pins, existing infrastructure, and to map the shoreline.

All data is contained within the GPS computer and later downloaded to a GIS/CAD workstation where the raw data is processed, evaluated, and cleaned as needed. With bathymetric and shore data captured we also add other suitable data such as BC TRIM maps (+/- 10 meter accuracy 90% of the time) which are very suitable for this purpose and are generally a necessary component of any resource based activity. These maps contain terrain details such as land contours (above sea level), creeks and rivers, roads and utilities.
Aerial photography geo-reference or orthorectified for the site are also utilized as they can aid in evaluating land based impacts to the site such as fish bearing tributaries, debris hazards such as rock falls or torrents and overall size orientation to land, sea, and fetch.

Design/Engineering/Modeling/Monitoring

With accurate site details it is possible to begin designing an efficient and robust anchoring system or installation. Through the use of GIS and CAD we develop the complete model for the system so that every part of a system is located, engineered, and specified appropriately. The computer model is important in that you can quickly build a system to generate accurate material and cost schedules, working drawings, fully 3D models to view, evaluate, and change parts of the system. This GIS/CAD component also ensures that license holders put their best foot forward with regulatory agencies in that installations are designed and built using proper and defensible techniques. Very important is that these GIS/CAD models will serve as the database for future compliance monitoring of the system and site in an environmental context. Mooring Systems designed to date for depths to 655 metres.

Environmental Monitoring

Acoustical Doppler current meters can be deployed at various depths to record current speed and direction, wave height, water temperature etc. depending on requirements.
Water column sampling and benthic bottom samples devices can be deployed. Analysis of the data collected can be done through our affiliated labs.
Sub-bottom profiling to determine sedimentary sea bed structure can be done in conjunction with sonar scans.

Underwater video by scuba divers or ROV can be utilized to provide photos of the sea bed or underwater structures. Please follow link to www.suboceanic.net fore more details.

Structural and Condition Surveys

Underwater surveys, including ultrasound thickness scanning and video, can be undertaken for structural integrity and condition analysis of floating and fixed structures.

Project Management and Installations

Ocean Dynamics Canada Ltd. will contract to manage the installation and/or mooring of floating and fixed structures. This also includes hydro and communications cable laying.

Tugs, Barges and Cranes etc. available from sub-contractors for any area.

Research and Survey Vessels Ocean Dynamics Canada Ltd.

MV "Crown Royal" 34' Quick Response Research and survey vessel with twin diesels, hydraulic davit and capstan.
MV "DynaCat" 24' Quick Response Research and Survey Vessel. Trailer able to any location.
MV "Kokanee" 22' Quick Response Research and Survey Vessel. Trailer able to any location.