What can the sonar and what is it used to in the first place?

There is some reliance on what can be achieved with a sonar.Especially among those who do not fish, it seems sounder regarded as something of Fisheries doping and foul means to catch fish with.

Once you have fished for a while one discovers that this in fishing was not so simple. You realize that it is not good enough to find the fish in the dark and let chance decide whether it is salmon or meatballs for dinner. A fisherman would use his knowledge to find and catch fish and then enjoy the triumph when one has actually caught the fish for reasons other than luck and chance.
To be able to use their intelligence to fishing, one must be able to make logical choices, and to be able to make logical choices, one must have access to information as a basis for their decisions. This is where the sonar is received. Contrary to popular belief, used sonar did not

primarily to search for that particular fish you intend to capture.Searching salmon sonar is theoretically possible, but works poorly in practice due to all sources of error.

What sonar can contribute, is to be your eyes downward, so that
You can observe the underwater environment and the existence of any schools of bait fish on the spot. That 90% of the fish found in 10% of the water column is a truth that agree very well, and it is with sonar use, you can find the right settings where fishing may occur.

The fisherman must know what he is looking for and be able to recognize it in
The solder screen, when you encounter it, for some crystal clear notice of the existence
salmon in the water or not, do not give sonar by itself.

Sonar is used primarily for three things:

• First to observe the depth and bottom topography in order to determine whether this is a place where the salmon would thrive.
• 2nd To avoid running gear on the bottom or to run the boat aground.
• Third Being able to locate places where there is food for the salmon.

Sonar is a very blunt tool. It is not a television picture of the underwater world to get on the screen. The technical and physical limitations set very definite limits to how much and what a sonar can detect and present to the user. By using the one must be aware of technology’s limitations and confounding factors to not be “fooled” by sonar and think they see something other than what it
really is. The purpose of this article is to clarify the technology behind the to draw the right conclusions from what the sonar display for us.

Water is a difficult medium of communication. Light has a very limited range of water and electromagnetic waves radio communications as well. The least bad of all means of communication underwater is sound. As the name suggests, sonar, it’s about
send off a short beeps and wait for an echo from an object which the sound wave encounter.

A sonar thus needs to consist of a speaker, a microphone and a device that responds when the echo comes. The distance to the object
echo comes from, is calculated with the time delay between sending audio shock and echo. The speed of sound is about 1500 m / s in water.

“The speaker and microphone,” consists of a single component and is called the donor. The sensor consists of a crystal that bends when the exposed for an electric current. If the stream then changes direction continuously (alternating current), you get the crystal to bend back and forth just as a speaker. From the sonar is thus a very short alternating shock
with about 200 000 Hz frequency, and it may be the transducer (crystal) to swing with the same frequency.

From the transducer, it is now an audio shock of 200 000 Hz through the water towards the bottom. The sensor also functions as a microphone. Bend the crystal so generates a stream. When the echo reaches the sensor to set it in motion by sound wave and generates a current that sounder in turn registers.

In broad terms, this is how it works and summarize it, it looks like this:

• First broadcasting of sound pulse and timing starts.
• 2nd Waiting for echo. Timing in progress. (The sound goes with 1500 m / s).
• The third recording of echo and calculation of distances with the help of the time.

Then repeat everything again. Note that the only thing you can get out of echo
is the distance to the object and the strength of the echo.

One can not determine which direction the echo came from, or if there are multiple simultaneous echoes from multiple objects at the same distance or from a large.

Donors

What characterizes a sensor is its transducer angle. Sound pulse which
leaving the sensor is spreading in the form of a lobe with a certain angle.
Depending on how the sensor is constructed you can get sound propagation more or
less concentrated, and the boundaries are indicated by a degree of the donor.
It defines the angle between the sensor values ​​where sensitivity has subsided
with some value in decibels as the limit is not definitive, but decreases
gradually in the page.

The most common angles are from 80-20 degrees and with different sensors
angles are usually available as an accessory. The wider angles around 20
degrees are suitable mostly for use in shallower waters. The further
donors are given a larger “vision” but may, at the expense of a lower deep shooting ability.
Tiny sensors with angles down 8 degrees “takes” a lot better at
deep water, but “see” in return for a little less because you have the
principle drive straight over the fish of the solder must register detta. Givarens
“Vision”, specified by the donor angle, has no sharp boundaries but decreases gradually
from the center out.

A phenomenon of this section with decreasing sensitivity to the side is a
small fish that is directly below the sensor gives a strong echo, while a large
fish that are in lobens edge gives a faint echo. The fish reached
of lobens edge for a short time is struck by fewer lodskott and provides a
shorter arc. The result is that the sonar shows the little fish larger than
the big fish on the screen.

To items such as fish appear as “arcs” are explained by the donor
wide “vision”. The fish are on the “A” distance from the transducer, when
it reaches the edge of field of view. At the next lodskott are fish in the “B”
distance and when the fish is directly beneath the sensor is the distance
at least, “C”. On the way out of sight repeated distance “B” and “A”
again.

This will be a distance variation in the form of an arc during the time the fish is in the sensor field of view.The bow is not a picture of the fish with “A” would be an end of the fish, “C” center of the fish and the last “A” the other end of the fish.
The bow consists of five echoes of the whole fish and not parts of it. The bow is not an image of the fish form by any means. Image Loading …

The monitor

Sonar equipped with screens of different size, resolution, number of gray scales
and in some cases even with color. The monitor is by far the most expensive single component in a sounder and so is the screen quality of the factor
affect the price the most. The information sonar displays the user is
almost exclusively with liquid crystal displays (LCDs).

The screen is divided into columns, each column shows the result of a
lodskott. For each lodskott stepped image one step to the left and on the
way built eventually an entire screen by a series lodskott.Som
already mentioned before the technology can only handle one lodskott at a time,
therefore only the column on the right is fresh and the rest of the screen shows
when the results of previous lodskott and history. The speed with which
screen ladders, due to waiting for an echo.

The waiting period will obviously be different depending on how deep it is and why
the screen will “go at different speeds” if lodar in shallow or deep water.
When you pass an object is determined the length of the screen
one thing, namely the number lodskott consecutive hits the object. The
This gives rise to very different results on the screen depending circumstances.

We see the same fish at the same depth at different
circumstances with the boat in motion, see pictures below.

The images reveal that the length of the arc hardly be interpreted as the length
on the fish. The fish can stay different lengths of time in the lobe, depending on whether
it moves, in which direction it is moving and if it crosses the lobe on the
widest point in the middle or just highlights the edge of the lobe.
The only thing that can give some indication of the size of the fish is the arc
thickness and strength of the echo (on the solder can prove it), but this requires
understood that the fish passes through the middle of the lobe.
Arcs in the example is as ideal as the store simulator. In reality,
it is rare with perfect arches. The fish moves and moves slightly
between each lodskott and the boat rolls. In reality, arcs rather
shaky and irregular.

The actual sonar

Sonar consists essentially of a device that generates an alternating current that
power sensor and a receiver that receives and processes the signal
that the sensor returns when the echo comes. The inrush current that drives the sensor is characterized by frequency, pulse length and power.

The frequency the sound pulse sonar work affects the solder properties.High frequency, 200 000 Hz or more allows a good detail separation. Lod, which works with lower frequencies, around 50 000 Hz has a superior depth-climbing ability, but more difficult to register small items such as fish. In sportfiskelod choose the higher rate in order to see more details such as fish.

Pulse duration (= Ljudstötens length) also affects the detail separation and deep shooting ability. Long pulse takes great depth, while a shorter pulse allows for a more detailed separation. Normally change the pulse duration automatically depending on the depth sounder.

The effect is a simple parameter to understand, high power is good for short. Some confusion may however arise in how manufacturers measure the effect. Depending on the mätnorm use yields a different power values ​​at equivalent sonar. Two different ways to indicate the effect occurs, the RMS (root-mean-square) and PP (peak-to-peak). The figures differ by factor of 8 between these two standards. If you multiply an RMS value of 8 may be the equivalent in PP. Good to know when to compare the effects indicated by different mätnorm.

Besides all this, the sonar a lot of processing power, memory
and more to to guide the process, process data, control the display
and all the rest.

What is what on the screen?

Now that we have passed out at least the greatest potential for misinterpretation
of what the sonar display and had a healthy skepticism about what we see, can
Let’s look at a fairly typical screen image and analyze it.
The figure shows that we conjure in 2 knots speed from an area of flat
and soft bottom and moving closer to a foundation. We currently have 40 feet of water
under the keel and the boat is in the middle of the small schools of fish that we see
only part of the right screen edge.

 

At the top of the image appears ytstörningar. This is disturbing echoes from among
other water and the boat and is thus not fish or something
Another interesting. A filter can reduce this. At about 15 m depth just
above the thermocline is a bigger fish. Gods knows what it
is, but just the fact that a larger fish are in the free
water column gives hope of a pelagic predator fish, like salmon or trout.
Thermocline appears clearly on the screen and is typically stronger
and bends upward at the slope. A few schools of small fish is at the precipice.They
This shoals along with the occasional larger fish makes the place
highly interesting. The location indicated by the GPS and we will pass
here a few times with the rigs at various depths and perhaps also with
different bait sets. A few smaller fish is in the steep foothills,
the fish’s location at the bottom makes it uninteresting for us since salmon are rarely
is there and is probably something else.
We also see that the bottom of the image changes from soft bottom with
diffuse echo to a hard bottom with sharper echo as we approach
shoal.

What we see in the picture is a fairly typical scenario. In connection with the
basis and especially on the slopes, there often lives. However, it is
quite difficult to draw definitive conclusions about what is what but just
the fact that there is much life in the water around the depth where
salmon tend to be good news.

Sonar other functions

Sonar equipped with a number of features and functions of various value for the fisherman.

Log
Airspeed indicator, which requires that a sensor is installed. An important feature of trolling because you need to have a good handle on the go. The precision of this type logs all depends on how well you succeed in the position of the transducer. With a successful investment, you can get an acceptable accuracy.

Water temperature
Temperarurgivaren is usually integrated with log transducer.Temperature limits are often the haunt of salmon and trout. The temperature of the water also reveals a certain extent, the depth at which it pays to fish. One of the more useful features for a trolling fisherman.

Filters
Sonar equipped with various types of electronic filters for the treatment of the echo. A lot of noise sources are as happy to make the image difficult to interpret and unclear. A type of filter to suppress strong echoes from the upper water layer and another suppresses occasional stray echoes Please fill the screen. All filters will help in any way to make the image more clear, but as word filters suggests filtered anything away. A filter is going to shut down and its effect should be adjustable by the user. Filters should always be set to the minimum effect that gives a perfectly acceptable otherwise take the filter away even that which you want to see.

Fish Symbols
A function with no value for a fisherman, could possibly entertain the kids for a while. Letting unintelligent electronics replace the screen image with fish symbols replacing an already difficult to interpret information with a misleading.

Alarms
An adjustable ground alarms are useful for trolling. Helps the user to observe due before djupriggsänkena go to the bottom because you can not monitor the sonar and depth all the time. Reduces stress on fish in waters with large depth variations. Zoom
Part of the depth of field can be enlarged up to a portion of the screen. Great feature especially when fishing at great depths where the image would otherwise be very compressed.

General advice and tips

The sensor assembly determines sonar performance. Install the sensor in a
so that it can move and adjust if the first placement
was not as successful. This applies very much to the sensor log.
Use the filter functions as sparingly as we possibly can. Set
filter values ​​on the lowest acceptable filtering or turn them when the filter
not needed.
To be able to see fish on the sonar screen must be set high sensitivity.
Increase the sensitivity until the screen begins to fill up the disturbance and reduce
then känligheten only just enough to the computer screen becomes INTERPRETABLE.
The settings will be best if you disconnect all the automation and drives both
depth range and sensitivity manually.
Seemingly equivalent solder of different brands can differ very much in price.
What am I paying for? Quality parameters noticeable only after a time
use. More thoughtful features tailored for the particular target anglers and weather resistance are things you do not notice immediately.
Manufacturers who have manufactured products for that anglers have with time
learned what customers want and make sure that the sonar has everything a fisherman wishes.
That knowledge is worth an extra penny for it gives a sense of security in the solder
suitable for fishing and are not marred by annoying flaws.