GPS Orientation THE OFFICIAL NAME IS NAVISTAR

GPS Orientation

THE OFFICIAL NAME IS NAVISTAR GPS

NAVISTAR GPS NAVIgatonal System using Timing And Ranging Global Positioning System

GPS is a satellite navigation system developed by the US Dept. of Defense (DOD)

GPS provides continuous, all-weather, threedimensional positioning information (position, speed and time)

How does GPS work? GPS is a satellite navigation system developed by the US Dept. of Defense (DOD). F GPS provides continuous, all-weather, three-dimensional positioning information (position, velocity and time). F F GPS is used by aviators, mariners, surveyors, truck and auto operators, and hikers.

5 ft wide 17. 5 ft long 1, 860 lbs

Delta II

Confused yet?

How GPS works in a few logical steps

The basis of GPS operation is ‘triangulation” from the overhead satellites in view.

In order to triangulate, your GPS receiver measures the distance from a satellite using the time of travel of the radio signals from the satellite.

In order to measure time of travel, a GPS set needs very accurate time which is achieved with some electronic tricks.

Along with the distance, the satellite must know exactly where it is positioned in space at all times. High orbits and careful monitoring are required.

All delays that the GPS signal experiences as it travels through the atmosphere must be corrected.

ANIMATION

Specifications Accuracy F GPS 10 meters(33 ft) 95% of time F DGPS < 10 meters (33 ft) F Availability--99. 85% F Coverage--world of time wide

SUMMARY F GPS Fixes are not error free – User and/or Satellite clock bias. – Satellite signal can be blocked. – Atmospheric interference is possible. – Poor satellite geometry is possible. You must monitor these errors on your GPS receiver.

Signal Quality and Accuracy The height of the bars in display shows signal quality from each satellite The number of items show the positions of satellites currently in view to your GPS.

Dilution of Precision Good Geometry Poor Geometry

Estimated Position Error “EPE” Many GPS units display “EPE” It uses satellite geometry plus other calculations to improve the accuracy of the estimated position error. “EPE” can be expressed in feet or meters. It is a user choice.

CEP = Circular Error Probable SEP = Spherical Error Probable SA – Selective Availability Error

DGPS (operated by USCG) enables local corrections for errors

DGPS Series of coastal stations broadcast corrections to GPS signal. F Former RDF stations used for this purpose. F Note: Stations on Great Lakes not shown on this illustration F Accuracy improved to better than 10 meters.

24 hours 5/1/2000 24 hours 5/2/2000 With 95 % of the time within 45 meters within 6. 3 meters or 148 Feet or 21 Feet

WAAS – Wide Area Augmentation System of ground-based reference stations and two stationary satellites that broadcast precision differential GPS corrections.

Typical GPS with SA OFF) Be sure that the GPS that you purchase has WAAS Less than 10 WAAS capability. feet of error Typical DGPS

Other things to consider when buying a GPS set.

Intended Use How are you going Imagine your worst case scenario: to adjust – Stormy conditions. or read – Waves beating on the hull. – your GPS set in Boat bouncing back and forth. – Windshield covered with salt spray. these let go of the helm without – You can’t conditions? F losing control of your boat.

Mounting Capability Think about the magnetic influence that your GPS will have on your compass! v. Mount near the helm. You can’t just lay the GPS v. Swivel capability so that it can be used or read by others. on the dash. v. Adjustable for sun glare. Think offrom theworst case your weather. v. Protected scenario. v. Ability to view satellites.

Screen Size F Can you read the display at a distance? F Avoid sets with tiny numbers and letters. F Some sets sacrifice readability for more chart area on their screens. F If you can’t clearly read the screen at an arm’s length, you won’t be happy with the set in stormy conditions.

Waterproof versus Submergible Waterproof means that the device will survive a little dampness. Water Resistant means it won’t last long in a moist, damp marine environment. Submergible means that the device will survive a dunking in the ocean.

Display Lighting Buy a back-lighted display so you can view it at night, Color displays are usually easier to read than black and white. Viewable in bright sunlight. Glare resistant screen.

12 v Attachment FBe sure your set comes with a power cord that will attach to your boat’s 12 V system. FCarry spare batteries for backup.

Chart Plotters It. Fis not have but practice to be Nice to a safe not really necessary. a chart plotter gazing at F Colored charts are a definite monitor when you should plus. be focusing on the other F Paper charts are easier to read boats sunlight. in bright and obstructions around you.

Remote Antenna Need GPS need a clear view of the satellites. May need a remote antenna on your boat.

Remote

Used Sets The price is so low. buy new! The best price for a used set is FREE.