Overview; How The Ns25 Works; Gps; Sonar - Humminbird NS25 Operation Manual

Overview

How the NS25 Works

Congratulations on your purchase of the Hummingbird NS25. The NS25 uses GPS and sonar
capability to determine your position, display it on a map, and provide detailed underwater
information.
The NS25 consists of four primary components; the control head, GPS receiver (SAT MAX), card
reader and transducer. The control head contains the user controls and display. The GPS
receiver receives signals transmitted by the constellation of GPS satellites orbiting the earth. It
selects four or more satellites whose position and signal strength provide the most accurate
position. From these four satellites, the GPS receiver calculates time, boat position
(latitude/longitude), boat speed and direction of travel. The card reader displays electronic map
information from the cartridges installed. The transducer is mounted beneath the water surface
and converts electrical energy from the transmitter into mechanical pulses or sound waves. The
transducer also receives the reflected sound waves and converts them back into digital signals
for display on the sonar unit.

GPS

The Global Positioning System (GPS) is a satellite navigation system designed and maintained
by the U.S. Department of Defense. GPS was originally intended for military use, however,
civilians may also take advantage of its highly accurate position capabilities, typically within +/-
100 meters. This means that 95% of the time you will be within 300 feet of your actual position.
Further capabilities are possible with the Differential Global Positioning Systems (DGPS), which
operate to refine satellite signal to the most accurate position possible
GPS uses a constellation of 24 satellites that continually sends radio signals to the earth. Your
position is determined by receiving signals from four or more satellites and measuring the
distance from the satellites to determine your present position.

SONAR

Sonar uses sound waves to determine the presence and location of underwater objects. The time
measured between the transmission of the sound wave and the reception of any reflection is
used to determine distance. The transmit and receive cycle is very fast. A sound wave can travel
from the surface to a depth of 240 feet and back again in less than ¼ of a second, so it is unlikely
that your boat can "outrun" this sonar signal. Analysis of the reflected signal can also be used to
determine location, size, composition, etc.
NOTE: Actual depth capability depends on such factors as bottom hardness, water conditions,
and transducer installation. Units will typically read deeper in fresh water than in salt water.
After spending a few minutes with your NS25 on the water, you will see the unit's ability to
accurately portray the underwater terrain, suspended targets, GPS position, and your position on
a map.
Your NS25 comes with everything necessary for installation and operation on most boats. The
transducer included, XT-6-20, is designed for mounting on the transom of the boat (directly
exposed to the water). On fiberglass hull boats , this same transducer can be bonded to the
inside of the hull. When mounted inside the hull, the sonar signal actually passes through the hll
of the boat. Both mounting techniques produce acceptable results on most boats.