Surveying

EDS is committed to providing the most accurate and repeatable bathymetric surveys available in the State of California.  We fully understand the importance of ensuring that the vertical datum for each survey is as "tight as it can be". This "tightness" is achieved through paying special attention to survey equipment calibrations, as well as  providing each project the most accurate benchmark available.

Before boats hit the water, ample mission planning  time is taken in order to ensure that only the most current and local benchmarks are used as a basis for our survey networks.  We always present a field plan to our clients which outlines the project survey datum, benchmarks and proposed survey coverage in order to ensure that our deliverables exceed our clients' expectations.  Each project benchmark is set by Thomas Tucker PLS 4460.

The most common problem in accurately measuring the seafloor with any sonar-based system is the calculation of the tidal elevation offset. Commonly a tide staff or electronic gauge is deployed in one location near the survey site and is used to calculate the tides for the entire survey area However, it is widely understood that non-linear tidal phenomena, phase lags and tidal gradients can drastically influence the tidal elevation spatially throughout a slough channel and therefore the use of a single point measurement is often unreliable.

To avoid these potential tidal elevation errors which can translate into significant departures from the true bottom depth, EDS uses geodetic Global Positioning Systems (GPS) with real-time kinematic (RTK) baseline processing that is integrated with our singlebeam and multibeam and inertial navigation instruments. The motion and Geoid 03 compensated positions and orthometric elevations of the RTK-GPS data stream are tagged with each sonar ping. In effect, the RTK-GPS mounted on the hydrographic survey vessel acts as a roving tide gauge collecting the most accurate tidal measurements throughout the survey area.

EDS offers bathymetric, topographic and geophysical surveying services in all types of environmental settings. Our surveying services include:

• Singlebeam surveys
  
• Multibeam surveys
  
• Side scan sonar surveys
  
• Sub-bottom profile surveys
  
• Beach profile surveys
  
• U.S. Army Corps of Engineers Class 1 pre and post-dredge payment surveys
  
• Condition surveys
  
• Monitoring surveys
  
• Reservoir sedimentation surveys
  
• River and creek channel and floodplain surveys
  
• Habitat surveys (Eelgrass, benthic and seafloor classification)
  
• Subsidence monitoring surveys
  
• Habitat restoration as-built and monitoring surveys