ALFATTAN CONTRACTING fleet of marine equipment is appropriate for all species of marine construction projects. From our flat barges, tug boats, work boats, portable boats, Dredger plants (Mechanical Dredger & Hydraulic Dredger), Excavators, Dozer, Crawler Crane (45-ton, 80-ton & 250-ton) and dump trucks. Our vessels are inspected and are operated by licensed pilots.
ALFATTAN CONTRACTING provides marine salvage services, ALFATTAN CONTRACTING have high qualified crew, a suitable vessel and equipment to serve ship / boat incidents. Marine salvage works include soft groundings, hard groundings, vessel sinking’s and hurricane damage.
Underwater Inspections & Survey
Dive inspections with experienced certified commercial divers.
Underwater Cutting & welding.
High-resolution Single Beam Echo-sounder Hydrographic Surveys
Single beam echo sounders (SBES), also known as depth sounders or fathometers determine water depth by measuring the travel time of a short sonar pulse, or “ping”. The sonar ping is emitted from a transducer positioned just below the water surface, and the SBES listens for the return echo from the bottom. In reality, the sonar energy will be reflected by anything that may be in the path of the sound – fish, debris, aquatic vegetation and suspended sediment.
Hydrographic survey grade single beam echo sounders are able to provide accurate bottom depths by distinguishing the real bottom from any spurious signals in the returned echo. True survey-grade hydrographic single beam echo sounders record a digital water column echogram or echo envelope, that provides a graphical representation of the return echo. Historically this information was presented on a paper chart recorder using thermal paper to provide the surveyor with a means to qualify sounding accuracy. SBES may use various different sonar frequencies; typically, 200 kHz is used in shallow water under 100m.
As the attenuation of sound in water decreases at lower frequencies, 24-33 kHz is commonly used for deeper water surveys. Often, two frequencies are combined for convenience into a single dual frequency transducer, e.g., 33/200 kHz. For surveys when suspended particulates are very high, usually when dredging is taking place, the low frequency sonar is able to penetrate the thick resuspended layer and measure the undisturbed hard bottom beneath. Transducers may be selected with different beam widths, which determines the size of the ping footprint on the bottom. Narrower beam transducers provide a smaller personified area and therefore present a depth measurement at a more discrete point under the survey vessel.
To determine the exact position of bottom features, narrower beam width transducers are desirable. Inexpensive depth sounders may offer a very wide beam width, presenting a low potential for accurate depth measurement. Lower frequency transducers typically have a wider beam width than high frequency options; the transducer needs to be larger to generate a directional beam as the frequency decreases. Single beam echo sounders offer significant cost savings compared to multibeam echo sounder systems and are especially useful in very shallow water, under 5-10m depth. Results from single beam echo sounders are easier to interpret, far less time-consuming to edit.