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Tide gauges (new)

 

An accurate measurement of sea level is very hard to pin down. But it is an important measurement for two main reasons:

 

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By having an accurate sea level measurement, it is possible to measure the height of everything on land accurately.

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By knowing sea level, we can determine if the oceans are rising or falling over time.

 

The problem with measuring the sea level is that there are so many things that perturb it. If you could take planet Earth and move it out into deep space so that the sun, moons and other planets did not affect it and there were no temperature variations worldwide, then everything would settle down like a still pond. Rain and wind would stop, and so would the rivers. Then you could measure sea level accurately. If you did this, the level of the ocean's water projected across the entire planet would be called the geoids. On land, you can think of the geoids as the level that ocean water would have if you were to dig a canal from the ocean's shore to any point on land.

 

But the Earth is not in deep space -- it is in the middle of a chaotic solar system. There are all sorts of things changing the water level at any given point, including:

 

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The tides, caused by the moon

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Large and small waves caused by wind and the tides

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High- and low-pressure areas in the atmosphere, which change the surface level of the ocean

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Temperature changes in the ocean, which change the density and volume of the water

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Rainfall and river water flowing into the ocean

 

If you were to stand on the ocean shore and try to measure sea level with a ruler, you would find it to be impossible -- the level changes by the second (waves), by the hour (tides) and by the week (planetary and solar orbit changes). To get around this, scientists try using tide gauges. A tide gauge is a large (1 foot [30 cm] or more in diameter), long pipe with a small hole below the water line. This pipe is often called a stilling well. Even though waves are changing the water level outside the gauge constantly, they have little effect inside the gauge. The sea level can be read relatively accurately inside this pipe. If read on a regular basis over a time span of years and then averaged, you can get a measurement of sea level.

 

You can see that getting an accurate reading (for example, down to the millimeter level) is extremely difficult. Satellites are now used as well, but they suffer from many of the same problems. Scientists do the best they can, using extremely long time spans, to try to figure out what the sea level is and whether or not it is rising.

 

LMS is taken this as serious in order to solve the problem of its customers and is soon going to launch the variety of tide gauges which are best in present market of tide gauges.

 

(For detailed specification please contact us on e-mail or call us)

 

 

Acoustic Doppler Current Profiler (ADCP) (new)

 

What is it and why do we use it?


An Acoustic Doppler Current Profiler, or Acoustic Doppler Profiler, is often referred to with the acronym ADCP. Scientists use the instrument to measure how fast water is moving across an entire water column. An ADCP anchored to the seafloor can measure current speed not just at the bottom, but also at equal intervals all the way up to the surface. The instrument can also be mounted horizontally on seawalls or bridge pilings in rivers and canals to measure the current profile from shore to shore, and to the bottoms of ships to take constant current measurements as the boats move. In very deep areas, they can be lowered on a cable from the surface.

How does it work?


The ADCP measures water currents with sound, using a principle of sound waves called the Doppler Effect. A sound wave has a higher frequency, or pitch, when it moves to you than when it moves away. You hear the Doppler Effect in action when a car speeds past with a characteristic building of sound that fades when the car passes.

The ADCP works by transmitting "pings" of sound at a constant frequency into the water. (The pings are so highly pitched that humans and even dolphins can't hear them.) As the sound waves travel, they ricochet off particles suspended in the moving water, and reflect back to the instrument. Due to the Doppler Effect, sound waves bounced back from a particle moving away from the profiler have a slightly lowered frequency when they return. Particles moving toward the instrument send back higher frequency waves. The difference in frequency between the waves the profiler sends out and the waves it receives is called the Doppler shift. The instrument uses this shift to calculate how fast the particle and the water around it are moving.

Sound waves that hit particles far from the profiler take longer to come back than waves that strike close by. By measuring the time it takes for the waves to bounce back and the Doppler shift, the profiler can measure current speed at many different depths with each series of pings.

What platforms are needed?


ADCPs that are bottom-mounted need an anchor to keep them on the bottom, batteries, and an internal data logger. Vessel-mounted instruments need a vessel with power, a shipboard computer to receive the data, and a GPS navigation system (so the ships own movements can be subtracted from the current data). ADCPs have no external read-out, so the data must be stored and manipulated on a computer. Software programs designed to work with ADCP data are available.

Advantages:

 

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In the past, measuring the current depth profile required the use
of long strings of current meters. This is no longer needed.

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Measures small scale currents

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Unlike previous technology, ADCPs measure the absolute speed of
the water, not just how fast one water mass is moving in relation
to another.

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Measures a water column up to 1000m long.

 

LMS Technogies Pvt Ltd is working in this field and soon going to launch latest in technology ADCP .For more queries and information please sends us an email or call us at our office.

 

 Our other projects/products in this category are :

 

Under Water Cameras (new)

Diesel Monitoring System (new)

Airborne Mineral Surveys (new)

Data Logging & Processing (new)

And many More

 

(For detailed information please feel free to contact us on phone or e-mail us)

 

        Send mail to lmstpl@eth.net with questions or comments about this web site.
               Last modified: 07/26/05