Transcript United States Power Squadrons ® Advanced Piloting Course Chapter 3 Fixes Fix Accuracy  Position Accuracy depends upon: • The technique used  GPS  Bearings  Radar • The.

United States Power Squadrons
®
Advanced Piloting Course
Chapter 3
Fixes
Fix Accuracy
 Position Accuracy depends upon:
• The technique used
 GPS
 Bearings
 Radar
• The geometry of the landmarks
 Angle between visible landmarks
 Shape and orientation of radar targets
Slide 2
Fix Accuracy – Bearing Geometry
Landmarks close together
Landmarks about 90° apart
2°
error zone
Slide 6
Fix Accuracy – Distance to Landmark
Landmarks close by
Landmarks at a distance
Slide 7
Simple Bearings from the Boat
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Slide 8
Limitations with Visual Bearings
 Multiple Bearings




Often difficult to get simultaneous measurement
Landmarks may not be separated sufficiently
Landmarks may be too far away
Possibly only one Landmark
 Two Bearings on same Landmark
 Sight landmark from different directions
 Second bearing somewhat later than first
 Called “Running Fix”
Slide 9
Running Fix
 Why?
 When two simultaneous bearings not available
 What?
 Advance an earlier bearing to overlay your current locale
and latest bearing
 How?
 Use distance run (dead reckoning) to determine how far to
advance the first bearing
Slide 10
Running Fix
Slide 12
Running Fix
Slide 13
Running Fix
Slide 14
Running Fix
Slide 15
Running Fix
Slide 16
Running Fix
Slide 17
Running Fix
Slide 18
Running Fix
Slide 19
Running Fix
Slide 20
Running Fix
Slide 21
Exercise 3-1
 Take out Bowditch Bay Chart
• EXERCISE 3-1
RUNNING FIX
 OBJECTIVE: Using two bearings on the same landmark and
advance an LOP to plot a Running Fix.
– At 0900, depart R”2” Fl R 4s Oyster River on a true course of
355. Speed is 6.0 Kn.
– At 0926, you take a hand bearing compass bearing of 310 on
Chapman Point Light.
– At 0951, you take a second compass bearing of 260 on
Chapman Point Light.
– With these two bearings, plot a running fix.
– What are the coordinates of the 0951 running fix?
– Seaman’s Eye: What can you use to confirm the accuracy of
the 0951 fix?
– At 0951, you take up a magnetic heading of 099. You
increase your speed to 12 Kn.
SOLUTION
Slide 22
Solution – Exercise 3-1
Slide 23
GPS Fix Accuracy
 Basic GPS (no SA)
• ~40 ft - - 95% (advertised)
• ~33 ft - - typical
 WAAS
• ~10 ft - - when receiving updates
More accurate than any other positioning technique
Slide 24
SKILL – Radar Fix
 Study Radar returns
 Compare with chart
 Look for identifiable features
• Distinct shorelines
• Isolated buoys
 Plot
• Convert relative bearings before plotting
Slide 25
Radar Fix Accuracy
 Bearing & Range
• Bearing - - 2° typical
 55 ft at short range
 300 ft at medium range
 650 ft at long range
• Range - - typical
 30 ft at short range (< ¼ nm)
 75 ft at medium range (< 2 nm)
 200 ft at long range typical (3 nm)
Slide 26
Position from Radar
Distance
to land
(VRM1)
Bearing
to buoy
(EBL2)
Bearing
to edge of
island
(EBL1)
Slide 27
Radar Fix - Buoy
Slide 28
Radar Fix – Prominent Feature
Slide 29
Radar Fix – Distance Off
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Slide 30
Radar Images
 Buoys are point targets
• Challenge: uniquely identifying the buoy
 Shoreline echoes are less defined
• Shapes change with each sweep
• Only see forward slope of shoreline
• Low-lying areas may not provide echoes
 Look for point features on shoreline
• Can get fix
 Look for prominent regions
• Can get distance from each feature
• Fix may be possible – approximate position more likely
Slide 31
Exercise 3-2 – Radar Fix
 Take out Bowditch Bay chart
• EXERCISE 3-2 RADAR FIX
 OBJECTIVE: Use a radar range and a radar bearing on
two objects to plot a radar fix.
– You depart RG “CP” Fl(2+1) R 6s at 0900 on a magnetic
heading of 112. Speed is 6.0 Kn.
– At 0950, you take a radar bearing of 357 magnetic from
the West end of Dutton Island and a radar range of 1.5 nm
from the southernmost coast of Dutton Island.
– Use these two lines of position to plot a fix.
SOLUTION
Slide 32
Exercise 3-2
Exercise 3-2
Radar Fix
Slide 33
Digital Charting
Digital Charting
 Digital Charts
• Based on Paper Charts
• Accuracy based on Scale of Chart
• Digital Charts are zoomed
 Can lead to false impressions
Slide 35
USPS Digital Chart CD
 Provided by MAPTECH, Inc.
• Chart Navigator Software
 Allows planning using digital charts
• Sample Charts
 Real charts – not for navigation (not updated)
 Training charts
– Bowditch Bay
– 1210 Tr (NOAA training chart)
 Included in Course
 For your use
 Optional material – not graded
 Can be used to compare with hand-plotted
exercises and cruise
Slide 37
Planning a Route on a Computer
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Slide 47
Waypoint List for Route
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Slide 48
Quick Route Building
enter start and
destination
route crosses
land
shortest distance
between the
two waypoints
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Slide 49
Adjusting Around Major Obstacles
adjust route to
avoid land by
adding points
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Slide 50
Scaling In to Refine the Route
add more waypoints
to refine the path
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Slide 51
Charts and Photo Charts
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Slide 53
Refining the Approach to Destination
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Slide 54
Homework
 AP Homework – Chapter 3
• EXERCISE 3- 2 RUNNING FIX
 OBJECTIVE: Using two bearings on two different landmarks
and advance an LOP to plot a running fix.
– At 1300, depart from a GPS fix of L 41° 45' N and LO 71° 55' W
on a true course of 230° and at
– a speed of 6.0 Kn.
– At 1330, you take a hand bearing compass bearing on “FI R6s
horn” of 318°.
– At 1355, you take a 2nd hand bearing compass bearing on
“Chapman PT- FI 6 S” of 280°.
– With these two bearings, plot and label a running fix at 1355.
– What are the two coordinates of the 1355 Rfix?
Slide 55
Homework 2 – where are we?
using Bowditch Bay
chart – based on
this screen
Where are you?
Which are buoys?
Slide 56
Questions ? … Comments
Homework answers follow
--- next week ---
Slide 57
Homework
Chapter 3 - Solutions
Solution to Exercise 3-1
Slide 59
Demo Homework 1 & 2
SOLUTION
Slide 60
Homework Solution
Slide 61
Slide 62