Coastal Navigation using GPS

1
Session III GPS DEPTH-FINDER UNITS
2

• 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

• The height of the bars in display shows signal
  strength from each satellite
• The clock faceshows the positions of satellites
  currently in view to your GPS.

4
Estimated Position ErrorEPE

• Many GPS units display EPE instead of HDOP
• Its an expression of the diameter of a circle in
  which your position target exists
• EPE is expressed in feet or meters user choice

5
(No Transcript)
6
GPS Setup Parameters

• True or Magnetic Direction
• Nautical/Statue Miles
• Clock 24hrs
• Speed in Knots
• Variation 013West
• Horizontal Datum WGS84
• Lat Lon Degrees/Minutes/Seconds

7
Course and Bearings

• Select a heading format
• TRUE
• MAGNETIC

8
GPS is not a Compass

• GPS reports movement over ground - often
  different than the vessels heading.
• GPS errors affect accuracy.
• Always steer off your compass, not the GPS.

9
Distance
When you are using your GPS on a boat, set the
Distance Unit of Measure to Nautical Miles.
10
Time Format

• Select a time format
• 12 or 24 hour clock format
• UTC or Local time

11
Speed
When you are using GPS on a boat, set the speed
unit of measure to KNOTS Nautical Miles Per
Hour.
12
Variation
Some GPS receivers are Automatic, some have to
be done manually. Variation is found on the
inside of the compass rose.
13
Horizontal Datum
WGS84

• WGS-84 is the US standard, NAD-27 is common.

14
LAT. LON.
Set GPS Unit to

• Degrees-Minutes-Seconds 074 23 - 39.0

• Most units are set
• Degrees-Minutes- Tenths of Minute
  074 23 .650

15

• CONVERSIONS

• Decimal portion of Minutes to Seconds
• .650 X 60 39.0

• Seconds to Decimal portion of Minutes
• 39.0 60 .650

16
DEPTH-FINDER
17
Depth Measurement
Set your depth sounder to correspond to the
vertical datum referenced on the nautical chart
that you are using.
Depth-Finder should be set for chart datumi.e.
Feet, Meters or Fathoms
18
Soundings in Fathoms
19
REMEMBER Your depth-finder shows
the depth of
water below you now, not where your going!!!
20
TRANSDUCER

• 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.

21
END OF Session III