gps, fish finder, boat part, marine supply, marine electronics

Anchor & Docking
Autopilot
Boating Accessories
Cabin/ Galley/ Deck
Communication
Electrical Supply
Electronics
Engine Parts
Fish Finder
Fishing & Sailing
GPS & Chartplotter
Instrument
Lighting
Marine Radar
Navigation Tool
Outdoor Gears
Plumbing & Pump
Safety
Steering & Control
Trolling Motor
Factory Refurbished
Specials
Rebate of Month
New Products

Shopping Cart
How to Order
Contact Us
Testimonials
FAQ & Return
Privacy Policy
Company Info
Site Map
Send me more info
Product Tutorials
Manufacturer Links
Link to Us
Government Order


Sign Up for Newsletter







gps, fish finder, boat part, marine supply, marine electronics
How to Order Shopping CartContact Us Shipping Info International Order
Marine Product Guides >

Marine GPS Guides





  • What is GPS?
    The Global Positioning System (GPS) is a space age navigational system that can pinpoint your position anywhere on the globe, usually within a few meters. This amazing technology is available to everyone, everywhere, day and night, and best of all, at no cost for use of the navigational data. GPS uses a constellation of 24 satellites in precise orbits approximately 11,000 miles above the earth. The satellites transmit data via high frequency radio waves back to Earth and, by locking onto these signals, a GPS receiver can process this data to triangulate its precise location on the globe. GPS operates 24 hours a day, in all weather conditions, and can be used worldwide for precise navigation on land, on water and even in the air. Some of its many current applications include: boating, fishing, hunting, scouting on land or from the air, hiking, camping, biking, rafting, pack trips by horseback, hot air ballooning, general aviation, snowmobiling and skiing, search and rescue, emergency vehicle tracking, 4 wheeling, highway driving and a host of other outdoor activities where accurate positioning is required.
  • How GPS Determines Your Position?
    GPS uses satellite ranging to triangulate your position. In other words, the GPS unit simply measures the travel time of the signals transmitted from the satellites, then multiplies them by the speed of light to determine exactly how far the unit is from every satellite it's sampling.
    By locking onto the signals from a minimum of 3 different satellites, a GPS receiver can calculate a 2D positional fix, consisting of your latitude and longitude. By locking onto a fourth satellite, the GPS can compute a 3D fix, calculating your altitude as well as your latitude/longitude position.
    In order to do this Eagle uses a 12 parallel channel receiver in all of it's current products. Three of the channels lock on to satellites for triangulation. Another channel locks on to a fourth satellite for 3D navigation, which lets the unit calculate altitude in addition to latitude and longitude. These four channels continuously and simultaneously track the four satellites in the best geometrical positions relative to you. The additional eight channels track all other visible satellites, then add this data to the data from the original four satellites. The unit then over-resolves a solution, creating an accuracy-enhanced reading. The additional channels also ensure reliable, continuous, and uninterrupted navigation, even in adverse conditions such as valleys or dense woods.
  • What is the accuracy of GPS? GPS was conceived in the 1970s, and is controlled by the United States Department of Defense. Although GPS was initially envisioned for military use, the Government realized early on that there would be numerous civilian applications as well. Subsequently, the Department of Defense created two transmission codes; the P code (Precision code) for military use, and the C/A code (Civilian Access code) for civilian use.
    The highest accuracy levels were to be reserved for the military so as to prevent hostile enemy attacks against the U.S. using our own navigational system. However, once in operation, the civilian GPS receivers using the C/A code proved to be more accurate than the D.O.D. had intended. Consequently, the military developed a system for randomly degrading the accuracy of the signals being transmitted to civilian GPS receivers. This intentional degradation in accuracy is called Selective Availability or S/A. This reduced the civilian GPS accuracy levels to being within 100 meters or less, 95% of the time. However, typical accuracy for most users averaged between 20 and 50 meters the majority of the time. You could easily see the effects of S/A on a GPS receiver when you were not moving. Typically there would be random movements in speed, altitude and position readings, along with slow position "wandering" on the plotter trail, easily seen when you are on a 0.1 or 0.2 mile Plotter scale, and not moving. For example, while parked at the dock in your boat, you would see unexplainable changes in your digital speed readings up to a few miles per hour, even though you were not moving.
  • What is a map datum?
    A datum is a mathematical model of the Earth which approximates the shape of the Earth, and enables calculations such as position and area to be carried out in a consistent and accurate manner. The datum is physically represented by a framework of ground monuments (i.e., trig stations) whose positions have been accurately measured and calculated on this reference surface. Lines of latitude and longitude on a map or chart are referenced to a specific map datum. Every chart has a map datum reference. The map datum is usually listed in the title block of the chart.
    If you are comparing the GPS coordinates to a chart or other reference, the map datum in the GPS unit should be selected to the same map datum that is listed as the datum used to generate the chart or other reference.
  • What is the MOB function?
    The Man Over Board (MOB) function is a common feature for marine GPS units. If a person falls overboard, the skipper uses this function to immediately mark the current location. The GPS goes into a "Goto" mode and directs the skipper back to the point where the button was pressed.
  • What is a route?
    A route is a series of waypoints entered in the order that you want to navigate them.
  • What is WAAS?
    WAAS stands for the "Wide Area Augmentation System".
    The Wide Area Augmentation System (WAAS) is an FAA funded project to improve the overall accuracy and integrity of the GPS signal for flying in instrument meteorological conditions, primarily during the approach to landing phase of flight. It is a space-based system that broadcasts integrity information and correction data as determined by ground reference stations. At this time the system is still in the development stage with a goal of providing reliable signals with an accuracy of 7 meters (21-22ft) both horizontally and vertically 95+% of the time. Current tests have shown the actual accuracy to be on the order of 2-3 meters.

    Sources of GPS signal errors

    Factors that can degrade the GPS signal and thus affect accuracy include the following:

    • Ionosphere and troposphere delays — The satellite signal slows as it passes through the atmosphere. The GPS system uses a built-in model that calculates an average amount of delay to partially correct for this type of error.
    • Signal multipath — This occurs when the GPS signal is reflected off objects such as tall buildings or large rock surfaces before it reaches the receiver. This increases the travel time of the signal, thereby causing errors.
    • Receiver clock errors — A receiver's built-in clock is not as accurate as the atomic clocks onboard the GPS satellites. Therefore, it may have very slight timing errors.
    • Orbital errors — Also known as ephemeris errors, these are inaccuracies of the satellite's reported location.
    • Number of satellites visible — The more satellites a GPS receiver can "see," the better the accuracy. Buildings, terrain, electronic interference, or sometimes even dense foliage can block signal reception, causing position errors or possibly no position reading at all. GPS units typically will not work indoors, underwater or underground.
    • Satellite geometry/shading — This refers to the relative position of the satellites at any given time. Ideal satellite geometry exists when the satellites are located at wide angles relative to each other. Poor geometry results when the satellites are located in a line or in a tight grouping.
    • Intentional degradation of the satellite signal — Selective Availability (SA) is an intentional degradation of the signal once imposed by the U.S. Department of Defense. SA was intended to prevent military adversaries from using the highly accurate GPS signals. The government turned off SA in May 2000, which significantly improved the accuracy of civilian GPS receivers.






Garmin GPS Guide


Raymarine GPS Guide


Furuno GPS Guide


Lowrance GPS Guide


Raymarine Chart Option



牋牋


__________________________________________________________________________________________


**The price is subject to change at anytime without any notice.  We are not responsible for any typographical errors.  Any products can be cancelled from sale at any time.

** All Products sold here are Brand New unless specified Otherwise and come with Full Manufacturer's Warranty



WarningWARNING: This product can expose you to chemicals including Di-n-hexyl Phthalate (DnHP) which is known to the State of California to cause reproductive harm, and Vinyl Chloride which is known to the State of California to cause cancer. For more information go to P65Warnings.ca.gov. __________________________________________________________________________________________



__________________________________________________________________________________________

Please contact us via email ask@wmjmarine.com or Call us at


__________________________________________________________________________________________

 


Customer Rating


Top Rated

We offer online shipment tracking

  

VeriSign Trust Seal
256-bit Encryption Shopping Cart

All personal information submitted is encrypted and 100% secure

__________________________________________________________________________________________


Garmin 
Products
Garmin Autopilot
Garmin GPS Chartplotter
Garmin Fishfinder
Garmin Radar

Garmin Trolling Motor
Automatic Identification System
 

Raymarine
Authorized Reseller
Raymarine Autopilot
Raymarine GPS Chartplotter
Raymarine Fishfinder
Raymarine Radar

Automatic Identification System

Simrad
Authorized Reseller
Simrad Autopilot
Simrad GPS Chartplotter
Simrad Fishfinder
Simrad Radar

Automatic Identification System

Lowrance
Authorized Reseller
Lowrance Autopilot
Lowrance GPS Chartplotter
Lowrance Fishfinder
Lowrance Radar
Lowrance Trolling Motor

Furuno
Authorized Reseller

 
Furuno Autopilot
Furuno GPS Chartplotter
Furuno Fishfinder
Furuno Radar

Automatic Identification System

Humminbird
Authorized Reseller
Humminbird GPS Chartplotter
Humminbird Fishfinder
KVH
Authorized Reseller
Marine Satellite TV
Marine Internet
JRC
JRC GPS
JRC Fishfinder
JRC Radar
ACR
Search Light
EPIRB
Personal Beacon
GMDSS VHF Radio

 
Cannon
Downrigger
Comnav
Marine Autopilot
Satellite Compass
Fusion
Marine Stereo
Authorized Reseller
 
Icom
Mounted VHF Radio
Handheld VHF Radio
Intellian
Marine Satellite TV
Marine Internet
Lewmar
Windlass
Bow Thruster
Sail Winches

 
Maxwell
Windlass
Minn kota
Trolling Motors
Motorguide
Trolling Motors
Revere
Liferaft

Authorized Reseller
 
Viking
Liferaft

Authorized Reseller
Seaview
Radar Mount
Xantrex
Battery Charger
Inverter Charger
Inverter
B&G
Authorized Reseller
B&G utopilot
B&G PS Chartplotter
B&G Instrument

 

Blue Sea System
Distribution Panel
Battery Charger

Seastar Teleflex
Boat Steering
Engine Control
Power Assist
Velair
Marine Air Conditioning

Navionics
Marine Chart

Si-Tex
Sitex Autopilot
Sitex GPS Chartplotter
Sitex Fishfinder

Sitex Radar
 

FLIR
Thermal Camera

Authorized Reseller
Mastervolt
Battery Charger
Inverter Charger
Inverter

OceanLED
Underwater Light

Lumishore
Underwater Light

 

Uflex
Steering & Engine Control

Lumitec
Underwater Light

International Dock
power pedestal

ProMariner
Battery Charger
Inverter Charger
Inverter

Newmar
Battery Charger
Inverter Charger
Inverter
DC Converter
DC Power Supply

 

Jabsco
Water Pump
Marine Toilet
Magnum
Authorized Reseller
Battery Charger
Inverter Charger
Inverter
Raritan
Water Heater
Waste Treatment

 
Rupp
Outriggers
Taco
Outriggers

 
Lee's
Outriggers
Actisense
NMEA Networking
Max Power
Bow Thruster
Stern Thruster
Mustang

Life Vest
Dry Suit
Work Suit
Immersion Suit

McMurdo

EPIRB
SART
Personal Beacon

Airmar

Sonar Transducer
Weather Station

Victron

Marine Isolation Transformer
Marine Battery Charger
Inverter Charger

Dometic

Marine Air Conditioning

__________________________________________________________________________________________


Recommended Site: WMJ Marine at Facebook   |  WMJ Marine at Linkedin  |  WMJ Marine at Twitter | Marine Electronics Store

Thank you for visiting WMJ marine for your Boating Equipment and Marine Electronics

Home | Anchor & Docking | Autopilot | Boating Accessories | Cabin/ Galley/ Deck | Communication | Electrical Supply | Electronics | Engine Parts | Fish Finder | Fishing & Sailing | GPS & Chartplotter | Instrument | Lighting | Marine Radar | Navigation Tool | Outdoor Gears | Plumbing & Pump | Safety | Steering & Control | Trolling Motor | Factory Refurbished | Specials | Rebate of Month | New Products
Our Company Policy | Privacy Policy | Shopping Cart

Marine Supply Specialist, USA - WMJ Marine Corporation

Copy Right: WMJ Marine Corporation 2004-2024