Terms Glossary Fishing, Sonar & GPS terms
By Barry Featheringill
Arch or Fish hook
way a liquid crystal display sonar unit shows fish. If a fish is
directly beneath you at some point while it was being displayed, it
will show up as an arch-shaped signal on the screen
is the time that a GPS receiver takes to determine a position from at
least three satellites.
A body of water (as an inlet or tributary)
that is out of the main current of a larger body generally shallow.
A submerged or partly submerged bank (as of sand or mud)
along a shore or in a river often obstructing navigation. Often found
at the mouths of rivers.
(Sonar Beam) A
sonar beam is the wide, cone-shaped projection of sound waves formed
as sound travels underwater . See also Cone angle
hardness refers to the density (or composition) of the bottom. This is
determined by interpretation of the sonar return. Hard bottom appears
thin and black, softer bottom returns appear thicker and less black.
Needs to be kept in mind that a sloping bottom may appear to be a
softer bottom than it actually is
Drop off with structure on it. Mistakenly used to mean any
sudden change in the bottom
A distinct line that leads to an abrupt change in the bottom
depth, composition or cover transition. This term can have several
meanings. Sometimes is used as term for a drop-off/ledge or it may
refer to part of a weed-line the fish are hanging on. Can also refer
to where rock meets mud or gravel.
rig separates the hook and worm from the lead with a leader.
To tie one, you slip a lead on your line, follow it with a bead and
then tie on a barrel swivel. A leader of varying length is tied to the
swivel and a hook tied to the leader. Hook size varies with the size
of the bait you plan to use.
is the effect of air bubbles created as boat motor propeller rotates
and move moves through the water.
(Creek or River) In
a reservoir the creek or river used before the lake was created. If
you looked at a cross-section these would be the deepest areas.
Topographical maps generally show creeks or rivers as hash-marked
line. Frequently on large rivers there are channels and there is a
drop-off that is associated with the edge of the channel created by
flow of the river.
Speed This is a usually controllable feature on sonar units
that sets the speed at which sonar information moves across the
display screen. Faster setting shows sonar information for more pings
and shows more detail, but information moves quickly across the
screen. A slower setting permits viewing more sonar history but not as
Navigation device that show Present Position on a Map, along with
track, waypoints and routes.
average size natural rock or boulder.
Hole Place where everybody and his brother/sister fishes.
Cone Angle The
theoretical shape taken by sonar signals as they disperse while
traveling through water. Although thought of as being cone-shaped, the
signals actually take more of a
suspended balloon shape.
This term is use in relation to weeds, trees, branches, buck
brush, tules, rock, stickups and/or man-made objects like docks. Cover
is often confused with structure the difference being cover is not
geological in nature. You
can have cover on structure.
Where the current with high velocity meet
up with a current with low velocity. Normally found in the same area
as eddy’s. (Note: fish will hang around the area of low velocity and
dart into area of high velocity when food source drifts past.)
Term for a small deep cove. In respect to a river it is where
the water flow has undercut the bank on the outside of a bend in the
The ability of
sonar unit to gather detail. How close sonar targets can be to each
other and still be recognized as separate by the unit.
Term referring to
a retrieve, or actually, a lack of retrieve akin to drifting with a
sudden or fast change in depth frequently associated with a creek
channel, point, flat or any combination of these. Contour lines on a
topographical map will be close together.
Drop shot, Down
shot Two names used in connection with a
finesse rig which places the sinker at the end of the line and the
hook or hooks above it without loops.
A key to sonar
operation. Sound emitted by the transducer which reflects off the
bottom structure or fish is the first echo, which the sonar unit
receives, interprets and displays on a screen
Where the current in a river or tidal water rotates back in
an upstream direction. Cause by something a point of land or large
rock. The eddy’s can vary in size.
An abrupt change in the cover or structure .
Area of the bottom of a body of water that
does not change more than a couple of feet in depth. A flat
will be represented by contour lines that are very far apart.
Where water is funneled down to pass through a section of
land such as between two islands or a manmade feature such as a
Global Positioning System is a satellite-based
navigation system made up of a network of satellites placed into orbit
by the U.S. Department of Defense. GPS was originally intended for
military applications, but in the 1980s, the government made the
system available for civilian use.
Is a technical
feature in the sonar involved in screening interference which is
designed to help display the relative density of objects on the
screen. This is an innovation of Lowrance
electronics which shows as a shaded area below a black target
line which can more clearly identify the difference between hard
bottom and grass or fish not part of the bottom. It can also show a
school of shad which are tightly
bunched and possibly in a
defensive mode due to predators on the feed.
An underwater island that normally rises
gradually. Will be shown on topographical map as contour lines that
create a circle or oval type shape.
causes sonar unit to display unwanted signals, or prevents desired
signals from being displayed. This is sometimes called noise,
is usually displayed as random dots. Most interference comes from electrical
(sparks or radio waves) or cavitational (air bubbles washing
across the face of transducer) sources.
Wood cover that lies horizontally and is almost parallel to
the water surface.
A severe drop-off. Commonly will be 70 to
90 degrees in angle and drops for more than 20 feet vertically.
Topographical map will represent this with contour lines that are very
map datum refers to particular survey of the earth’s surface that is
referenced when creating a chart (i.e. WGS84). This translates the
coordinates from the sphere to a flat surface.
stained or clear water meets dirty water. This is a condition that is
normally caused by winds blowing waves into a muddy shoreline. Can
also be the result of heavy boat traffic.
is the reference point of a compass. Magnetic North uses the magnetic
field of the earth to align pointer of compass.
True North uses the earth’s axis as reference point for
North. GPS units usually default to True North settings. (Note: GPS
heading may vary from compass heading)
Something (as a bend in a river) resembling an oxbow. Place
where river has created a shallow low current body of water that will
reconnect with river downstream.
rock that is no larger than ˝ inch in diameter. (Good area to check
during the spawn for bass)
abrupt hump that generally rises from deep water is small in area on
the top. On a topographical map will appear as a bunch of small circle
on top of each other.
picture elements or small blocks that make up the image of
liquid crystal display (LCD). This is measure in vertical and
horizontal numbers that indicates the quality of the resolution.
A shoreline feature where the shoreline makes a turn out into
the lake and cuts back on itself forming a peninsula. These can be
large main lake features at the opening of a creek arm or as small as
a boat. In natural lakes, a point may not be that obvious. It may only
be discernable by weed growth outlining the point underwater. In this
case, look at the weeds as if they were the shoreline. On a
topographical map, the contour lines make a two-sided triangle (for
lack of a better term).
that is on the main lake or the entrance to a large cove
that is inside a cove. These are smaller than a ‘primary point’
and are further away from the main lake.
amount of sound energy emitted into the water by sonar transmitter. It
is measure either as RMS (Root mean Square) or P-T-P (Peak To Peak).
Greater the power output the more signal penetration through weedlines
and thermoclines and reach greater depths.
the length of time that sonar sound burst is transmitted into water.
Shorter pulse widths provide better target separation, but do not
travel to great depths.
The ability of a sonar display to show the fine details.
man-made bank of rock. Found on the front of dams, points and front of
shore line properties.
of waypoints linked together is a specific order to show a path
between two points and saved in GPS memory. Route can be used when
travel between two or more locations as it is a more accurate and
faster method than repeatedly selecting separate waypoints each time
you travel the same area.
A narrow piece of land that extends out from the shoreline
(sometimes visible) and connects to an underwater island or
hump. This will drop down before it meets the underwater island then
it will again come up in depth . On a topographical map the contour
lines will appear as underwater point extending from the shoreline. As
lines extend from the shoreline lines on each side will get closer
together and then start getting further apart as they come closer to
the island or hump.
‘second return’ is a term that describes the appearance of a
second sonar return below the major return at exactly twice the true
depth. This second return is caused by the sonar signal bouncing off
the bottom once and rebounding to the water surface and then traveling
back down to the bottom to be reflected again. These second
returns are very common in shallow water or hard bottoms. The
secondary return can be a guide to set the sensitivity when in shallow
Control on sonar unit that determines how powerful a signal
will be sent through the transducer. Hard bottom requires a little
less sensitivity than do softer bottom.
Basic plastic worm technique which began with a splitshot
pinched on the line 18 to 30 inches above the hook. When drifted,
reeled or “pulled” with a low rod angle, in order to move the bait
along in a swimming mode. Has expanded to include any method using
light line fishing that separates the sinker and hook, with or without
An abbreviation derived from SOund, NAvigation
, and Ranging.
Term relating to what bass are doing in
the late winter/early spring in relation to Structure. Fish move up
from their deep water winter living area and will “Stage” on
primary points, channel bends, breaks, drop-offs and secondary points
before the move to the shallows. These staging area can often be very
concentrated on structure.
refers to the trees that are still standing in the water. Some trees
may still be alive or trees that were left standing when the lake was
created and have died.
Small dead bushes which are sticking out of the water.
Normally found near the shoreline or on shallow flats. These
‘stick-ups’ usually are no more than 4 feet tall.
method which actually relies on propulsion of the electric trolling
motor. Its use is actually banned my most tournaments
and especially the slight or subtle difference, in apportion of the
bottom. ‘Structure’ can be ledge, river channel, break, hump, etc.
in river run where
it creates a S form.
set Hook setting technique used by splitshotters. Since
small hooks and baits are taken easily by feeding bass, only a mild,
sweeping motion of the rod is required when line is tight to the fish.
This accomplished by bringing the rod across the body left or right.
than water that reflects enough sonar signals to be received and
displayed by the sonar unit. Can bee weeds, boulders, trees and
stumps, dense concentration of algae in the thermocline, baitfish, and
measurement of the minimum distance that fish-finder needs to be able
to recognize very close objects as distinct targets.
Water layers of different temperatures that create sonar reflections
due to the density of the differing water temperatures. Thermocline
will appear as a continuous band across the sonar display above the
High The time in which the tide is the highest.
Low The time when the tide is the lowest.
time in which the tide is going out.
time in which tidal movement is at it’s lowest. This happens four
times a day at each high and low tide
map Abbreviated term for topographical map that is the
best tool available to catalog and view the arrangement of things on
the Earth's surface. In referring to a lake it shows various depths.
of points that defines where you have traveled in the past on GPS are
called ‘Tracks.. Tracks are saved at regular time intervals. Tracks
are helpful to see hwere you have been and to be able to get back to
where you started.
that converts electrical impulses from transmitter into sound waves,
sends them into the water, receives sound waves and converts them back
into electrical impulses, and feeds them back to the sonar unit.
zone Change from one type of structure to another.
stands for Wide Area Augmentation System. WAAS is a complimentary
technology to GPS that provides enhanced accuracy through correction
signals broadcast from Federal Aviation Administration satellites.
With this signal the accuracy of GPS is improved.
tow different types of water mix. Where ocean or sea water meets
Dirty Water that has visibility of less than 6 inches.
Frequently, green or muddy.
where the visibility is greater than 10 feet.
that has a brownish or greenish color with limited visibility
Swill The heaviest, nastiest, weedy area in a body of water
Area of a weedbed where the weeds meet open water or one type
of weed meets with another type of weed.
Vegetation growing in the water that
creates an almost solid formation on the top of water. This frequently
will hold fish.
vegetation that comes to the top of the water’s surface and is
vegetation that does not come up to the water surface
A creek channel intersection.