1. Session III GPS DEPTH-FINDER UNITS

2. F GPS positions 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 can monitor these errors with your GPS receiver.

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

4. Horizontal Dilution of Precision F Horizontal Dilution of Precision (HDOP) is a measure of satellite fix geometry quality F Figure at far left has lower (better) HDOP F GPS receivers measure and display HDOP Good Geometry Poor Geometry

5. Estimated Position Error “EPE” F Many GPS units display EPE –It’s an expression of the diameter of a circle in which your position target exists –EPE is expressed in feet or meters – user choice

6. Specifications Accuracy F GPS without SA - 100 meters F GPS with SA - 10 meters(33 ft) 95% of time F DGPS – approx 10 feet, 95% of time F WAAS – approx 8 feet, 99.85% of time

8. GPS Setups – True or Magnetic Direction – Nautical Miles – Clock – Speed in Knots – Variation – Altitude – Horizontal Datum – Lat & Lon

9. Course and Bearings F Select a heading format: –TRUE –MAGNETIC

10. F GPS reports movement over ground - often different than the vessels heading. F GPS errors affect accuracy. F Always steer off your compass. GPS is not a Compass GPS is not a Compass

11. When you are using your GPS on a boat, set the Distance Unit of Measure to Nautical Miles. Distance

12. F Select a time format: –24 hour clock format –12 hour clock format Time Format

13. F Select a Time Setup. –UTC –Local time GPS Time Setup

14. When you are using GPS on a boat, set the speed unit of measure to KNOTS – Nautical Miles Per Hour. Speed Speed

15. Some GPS receivers are Automatic, some have to be done manually Variation is found on the inside of the compass rose. Variation

16. Set your GPS for the height of your GPS antenna at sea level. Altitude Mode Altitude Mode

17. Update your GPS with the HORIZONTAL DATUM referenced on the nautical chart that you are using. WGS84 Horizontal Datum

18. WGS84

19. F WGS-84 is the standard in US waters, NAD-27 is common. Different datums are used in foreign waters. F Becomes more important as local datum become increasingly offset from WGS-84. F Shown on the General Information Blocks of most charts/maps. Selecting the correct Datum

20. LAT. & LON. LAT. & LON. Set GPS Unit to F Degrees-Minutes-Seconds 074 – 23 - 39.0 Most units are set Degrees-Minutes- Tenths of Minute 074 – 23.650

21. F CONVERSIONS F Tenths of Minutes to Seconds F.650 X 60 = 39.0 F Seconds to Tenths of Minutes F 39.0 ÷ 60 =.650

22. DEPTH-FINDER

23. Set your depth sounder to correspond to the vertical datum referenced on the nautical chart that you are using. Depth Measurement Depth-Finder should be set for chart i.e. Feet, Meters or Fathoms

24. Soundings in Fathoms

25. Units of Measure - Feet –- Fathoms –- Meters Vertical Datum

26. REMEMBER Your depth-finder shows the depth of water you’re in, not where you’re going!!!

27. It is very important to know where the transducer is mounted You need to know the distance from your waterline to the transducer You also need to know the distance from the transducer to the lowest point of your boat. TRANSDUCER TRANSDUCER

28. Remember that the greatest hazard to navigation may be a bored navigator!!!!!!!!

29. END OF Session III