United States Power Squadrons Advanced Piloting Course Chapter

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 2

Fix Accuracy – Bearing Geometry Landmarks close together Landmarks about 90° apart 2° error zone 6

Fix Accuracy – Distance to Landmarks close by Landmarks at a distance 7

Simple Bearings from the Boat 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 one Landmark § Two Bearings on same Landmark § Sight landmark from different directions § Second bearing somewhat later than first § Called “Running Fix” 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 10

Running Fix 12

Running Fix 13

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Running Fix 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 4 s 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 22

Solution – Exercise 3 -1 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 24

SKILL – Radar Fix § Study Radar returns § Compare with chart § Look for identifiable features • Distinct shorelines • Isolated buoys § Plot • Convert relative bearings before plotting 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) 26

Position from Radar Distance to land (VRM 1) Bearing to buoy (EBL 2) Bearing to edge of island (EBL 1) 27

Radar Fix - Buoy 28

Radar Fix – Prominent Feature 29

Radar Fix – Distance Off 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 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 6 s 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 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 32

Exercise 3 -2 Radar Fix 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 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 37

Planning a Route on a Computer 47

Waypoint List for Route 48

Quick Route Building enter start and destination route crosses land shortest distance between the two waypoints 49

Adjusting Around Major Obstacles adjust route to avoid land by adding points 50

Scaling In to Refine the Route add more waypoints to refine the path 51

Charts and Photo Charts 53

Refining the Approach to Destination 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 R 6 s horn” of 318°. – At 1355, you take a 2 nd 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? 55

Homework 2 – where are we? using Bowditch Bay chart – based on this screen Where are you? Which are buoys? 56

Questions ? … Comments Homework answers follow --- next week --- 57

Homework Chapter 3 - Solutions

Solution to Exercise 3 -1 59

Demo Homework 1 & 2 SOLUTION 60

Homework Solution 61

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