# Plotting Celestial LOPs

## Presentation on theme: "Plotting Celestial LOPs"— Presentation transcript:

Plotting Celestial LOPs
Junior Navigation Chapters 8 & 9 and part of Chapter 13 THE OUTER SCALE IS READ FROM A MERIDIAN OF LONGITUDE. THE INNER SCALE FROM A PARALLEL OF LATITUDE. 090 270 180 000 080 070 060 050 040 030 020 010 260 250 240 230 220 210 209 190 100 110 120 130 140 150 160 170 280 290 300 310 320 330 340 350 360 200

Learning Objectives Set up a Constant Latitude Scale Small Area Plotting Sheet (CLS SAPS) Plot a single celestial LOP Plot a celestial running fix Meridian Transit of the sun Setup a Universal Plotting Sheet (UPS) – Chap 13

Plotting Techniques Errors result - working too fast - not checking plots Don’t rush Sharp-pointed pencil (medium/hard) Complete plot before labeling Erase unnecessary lines Recheck results if they differ by more than 0.5´ on CLS Sheets. Small variations are normal

Constant Latitude Scale Small Area Plotting Sheet
Directions from Compass Rose Latitude Scale fixed, you select Mid-Lat You create the Lo scale for your area using arcs on lower part of form 1’ 3’ 5’ 7’ 9’ 2’ 4’ 6’ 8’

Constant Latitude Scale Small Area Plotting Sheet
30’ Plot 1258 DR at: L 44º 50.6’ N Lo 92º 21.2’ W 30’ 20’ 10’ STEP 1 Label ‘Mid Lat’ that will allow plot to be near center of form. Label each of the 10’ increments. 45ºN 50’ 40’ 30’

Constant Latitude Scale Small Area Plotting Sheet
30’ Plot 1258 DR at: L 44º 50.6’ N Lo 92º 21.2’ W 45ºN 30’ 20’ 10’ 50’ 40’ 45º STEP 2 Lo varies to Mid-Lat Draw diagonal lines between the bottom center & preprinted values for selected Mid-Lat

Constant Latitude Scale Small Area Plotting Sheet
30’ Plot 1258 DR at: L 44º 50.6’ N Lo 92º 21.2’ W 45ºN 30’ 20’ 10’ 50’ 40’ 1º latitude 1º longitude 60nm x 60nm THE OUTER SCALE IS READ FROM A MERIDIAN OF LONGITUDE. THE INNER SCALE FROM A PARALLEL OF LATITUDE. 090 270 180 000 080 070 060 050 040 030 020 010 260 250 240 230 220 210 209 190 100 110 120 130 140 150 160 170 280 290 300 310 320 330 340 350 360 200 STEP 3 Intersections of diagonal lines and solid arcs mark locations of 10’ meridians Draw meridians Label meridians You are on your way in becoming a cartographer 20’ 10’ 30’ 40’ 50’ 92ºW 50’

Constant Latitude Scale Small Area Plotting Sheet
30’ Plot 1258 DR at: L 44º 50.6’ N Lo 92º 21.2’ W 45ºN 30’ 20’ 10’ 50’ 40’ 92ºW THE OUTER SCALE IS READ FROM A MERIDIAN OF LONGITUDE. THE INNER SCALE FROM A PARALLEL OF LATITUDE. 090 270 180 000 080 070 060 050 040 030 020 010 260 250 240 230 220 210 209 190 100 110 120 130 140 150 160 170 280 290 300 310 320 330 340 350 360 200 THE OUTER SCALE IS READ FROM A MERIDIAN OF LONGITUDE. THE INNER SCALE FROM A PARALLEL OF LATITUDE. 090 270 180 000 080 070 060 050 040 030 020 010 260 250 240 230 220 210 209 190 100 110 120 130 140 150 160 170 280 290 300 310 320 330 340 350 360 200 STEP 4 Plot your position 1258

Constant Latitude Scale Small Area Plotting Sheet
30’ Plot 1258 DR at: L 44º 50.6’ N Lo 92º 21.2’ W 45ºN 30’ 20’ 10’ 50’ 40’ 92ºW 1258 THE OUTER SCALE IS READ FROM A MERIDIAN OF LONGITUDE. THE INNER SCALE FROM A PARALLEL OF LATITUDE. 090 270 180 000 080 070 060 050 040 030 020 010 260 250 240 230 220 210 209 190 100 110 120 130 140 150 160 170 280 290 300 310 320 330 340 350 360 200 STEP 5 With sun intercept 4.0nm towards and azimuth 205º, plot your estimated position 1258 Sun EP L 44º 47.0’ N Lo 092º 24.5’ W

Constant Latitude Scale Small Area Plotting Sheet
30’ Sight reduced from FIX: Not an EP, do not draw a square Sight Error (SErr) intersection of LOP and azimuth 45ºN 30’ 20’ 10’ 50’ 40’ 92ºW 1258 GPS 1258 Sun S Err 4.0nm EP L 44º 47.0’ N Lo 092º 24.5’ W

Celestial Fixes Celestial fix - sights on two/more different bodies taken within a short time Time interval within 20 minutes - a “Fix” Time interval longer - a “Running Fix” Offshore navigators rely on Sun RFix Morning LOP advanced to midday Midday LOP advanced to evening Evening LOP advanced to next morning .

Plotting a Celestial R Fix
Advancing a LOP using a construction line that parallels the DR track 45ºN 30’ 20’ 10’ 50’ 40’ 0.9nm T 245º 0.8nm A 332º 0800 0900 C 260 S 6.0 1000 1100 0800 Sun C 200 S 6.0 260 1200 200 1200 RFix 1200 Sun Sun

Plotting a Celestial R Fix
Advancing a LOP using direction and distance between DR’s. 45ºN 30’ 20’ 10’ 50’ 40’ 0.9nm T 245º 0.8nm A 332º 0800 0900 C 260 S 6.0 1000 1100 0800 Sun C 200 S 6.0 THE OUTER SCALE IS READ FROM A MERIDIAN OF LONGITUDE. THE INNER SCALE FROM A PARALLEL OF LATITUDE. 090 270 180 000 080 070 060 050 040 030 020 010 260 250 240 230 220 210 209 190 100 110 120 130 140 150 160 170 280 290 300 310 320 330 340 350 360 200 1200 1200 RFix 1200 Sun Sun

Plotting a Celestial R Fix
Advancing a LOP using the original intercept and azimuth 45ºN 30’ 20’ 10’ 50’ 40’ 0.9nm T 245º 0.8nm A 332º 0800 0900 C 260 S 6.0 1000 1100 0800 Sun C 200 S 6.0 1200 1200 RFix 1200 Sun Sun

Sight Folder Plotting S Err 3.6nm 45ºN 30’ 20’ 10’ 50’ 40’ 40’ 10’
0858 Sun 1245 Sun 1245 RFix GPS S Err 3.6nm 40’ 10’ 93ºW 50’ 30’ 20’ 10’

Sight Folder Plotting Changing position where sights taken.
30’ 20’ 10’ 50’ 40’ Changing position where sights taken. Sun 0858 Sun 1245 Sun 1245 RFix 1245 GPS Resulting RFix must still be within 5.0nm of later sight. 0858 GPS S Err 4.0nm 40’ 10’ 93ºW 50’ 30’ 20’ 10’

Universal Plotting Sheets
Offshore: plotting & labeling of courses & bearings – referenced to TRUE Universal plotting sheets used in any part of the ocean except Polar Regions Likely to cross several lines of variation offshore. Using True, apply Var & Dev for each leg to determine Compass course to steer.

Universal Plotting Sheets
The UPS covers about 4° of latitude and 4° of longitude Draw meridian through marks on Compass Rose at desired mid-latitude 18 18

Universal Plotting Sheets
Setup for mid-latitude of 37° N and mid-longitude of 68° W 30 7 THE OUTER SCALE IS READ FROM A MERIDIAN OF LONGITUDE. THE INNER SCALE FROM A PARALLEL OF LATITUDE. 090 270 180 000 080 070 060 050 040 030 020 010 260 250 240 230 220 210 209 190 100 110 120 130 140 150 160 170 280 290 300 310 320 330 340 350 360 200 Will be used for chapter 13 homework cruise 30 7 19 19

Universal Plotting Sheets
Setup for mid-latitude of 37° N and mid-longitude of 68° W 68ºW 69º 70º 66º 67º 37ºN 38º 39º 36º 35º Set dividers to the spacing between central meridian and the one drawn Measure off and draw remaining meridians Label 20 20

Universal Plotting Sheets
68ºW 69º 70º 66º 67º 37ºN 38º 39º 36º 35º Distance & latitude -measured along Latitude scale on central meridian 35º 36º 37º 38º 39º Longitude - measured on pre-printed scale draw line across at value of mid-lat 21 21

Longitude Measurements
Measure 15’ of Longitude at 37° Latitude. Precision on UPS – 1.0nm or 1’ of Latitude/Longitude. 10’ 5’ + 22 22

YOU WILL USE THIS UPS FOR PLOTTING THE CHAPTER 13 HOMEWORK CRUISE
Universal Plotting Sheets 68ºW 69º 70º 66º 67º 37ºN 38º 39º 36º 35º 15º W Var (ZD+5) (ZD+4) Plot the 15º W isogonic line using points: L1 39º 00’ N, Lo1 69º 20’ W and L2 35º 00’ N, Lo2 66º 45’ W… Time Zone Boundaries Vertical dashed line, with ZD on both sides YOU WILL USE THIS UPS FOR PLOTTING THE CHAPTER 13 HOMEWORK CRUISE Isogonic Lines Lines of equal magnetic variation Dashed line, with variation shown 15º W Var 23 23

Universal Plotting Sheets
15º W Var 68ºW 30’ 69º 67º 68ºW 69º 70º 66º 67º 15º W Var 37ºN 30’ 38º 36º 37ºN 38º 39º 36º 35º (ZD+5) (ZD+4) (ZD+5) (ZD+4) 5 10 15 20 25 DOUBLING THE SCALE 15º W Var 15º W Var 24 24

Meridian Transit of Sun also known as Local Apparent Noon (LAN)
Celestial body crosses upper branch of observer’s meridian – body reaches maximum altitude LHA is 000° Body due north/south Azimuth 360º or 180º Nav. triangle collapses to straight line - elevated pole, observer, & GP of body - all on same great circle: the observer’s meridian Meridian Transit of Sun also known as Local Apparent Noon (LAN) Observer GP Sun Equator Greenwich Pn 25 25

Finding Time of Transit
Mean time of transit is calculated 26 26

Finding Time of Transit
Find ZT of MT on 14 Nov at Lo 092° 21.2´W Step 1 Record the DR Lo Step 2 Find whole hour GHA from daily page of Nautical Almanac, closest to, but still smaller than DR Lo 14 27 27

Finding Time of Transit
Find ZT of MT on 14 Nov at Lo 092° 21.2´W Step 3 Record GHA Step 4 Subtract whole hour GHA from DR Lo Step 5 Browse increments / corrections pages 18 28 28

Finding Time of Transit
Find ZT of MT on 14 Nov at Lo 092° 21.2´W Step 6 Record increment Step 7 Add to GHA whole hour Step 5 Correct for ZD 18 6 + ZD: 21.2’ / 60 = º / 15 = 6.15 29 29

Computing Latitude The Ultimate Backup
Determine Lat w/o calculator, tables, or plotting Simple and easy to teach to crew members Quick check of GPS latitude However, limited availability Only once a day, at a specific time Ann Changed wording of a few bullets 30 30

Computing Latitude Correct WT and hs of the sight at maximum altitude
Subtract Ho from 90° to obtain Co-Alt For UT of the sight, obtain Dec of sun from Almanac Combine Co-Alt and Dec to obtain your latitude L = Dec + Co-Alt 31 31

Computing Latitude Observer North of Sun 70 20 10 30 50°N Observer
CoAlt 70 Observer 20 10 Sun 30 Equator 50°S 32 32

Computing Latitude Observer South of Sun 30 60 20 40 50°N Sun Equator
CoAlt Observer 50°S 33 33

Taking the Noon Sight Begin taking sights 10 to 20 minutes before ZT of MT Take observations every minute or two Note altitude and time Rate of altitude increase slows as sun approaches meridian transit Near transit, altitude may appear nearly constant for a few minutes Helpful to plot run of sights 34 34