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Declination
- 1. Land Navigation Term:Magnetic Declination Website: http://www.ngdc.noaa.gov/ Go to “Geomagnetic Data” Go to “Declination” Go to “Compute your declination” (N38 °, W77°) What is the declination for Warrenton? What was it on this day in 1994? 1974?
- 2. Magnetic Declination Thenumber of degrees that a compass needle is pulled away from True North to point toward Magnetic North
- 3.
- 4. Magnetic Flux TheEarth’s Magnetic Field is NOT stationary You need current map or use a declination chart or website
- 5. Warrenton 1994 Diagram - True North – the top of the earth GN – Grid North – 1 ° 45’ MN – Magnetic North – 10 ° GN MN
- 6. Declination for Warrenton2009= 10 °9’ 1994= 9°54’ 1974= 7°47’
- 7. Why do weneed to know all this? So that we can navigate using a map , the ground and compass . You cannot follow a GN with a compass; nor can you plot a MN with a protractor. To assist you in making the conversion from MN to GN, and vice versa, a declination diagram is placed on the map margin. When using a map - use a protractor to measure GRID Bearings. Do not use the compass magnetic needle. When using the ground – use a Compass to Measure MAGNETIC Bearings.
- 8. From ground to map . You measure the bearing of a landmark on the ground with a compass. It is 321° MN. The G-M ANGLE on the Map is 10° So MN to GN ADD 321° + 10° = 331° GN Draw this angle on your map From map to ground . You measure the bearing of a point on the map with a protractor. It is 331° GN. The G-M ANGLE on the Map is 10° So GN to MN SUBTRACT 331 ° - 10° = 321° MN Put this on your compass Map Information – Direction CONVERSION for Western Declination
- 9. Warrenton 1994 Diagram - True North – the top of the earth GN – Grid North – 1 ° 45’ MN – Magnetic North – 10 ° IF you read 90° (east) on your map, what should your compass reading be to walk directly east? GN MN
- 10. Remember which Northyou are using! On your map decide if you will use: The True North (Outside border lines) The Grid North (The inside grid lines) Use the Magnetic to Grid or Magnetic to True conversion
- 11. How to Orienta Map Find the declination diagram in the map's margin. Note the degree. Line up one of the long sides of the compass with one of the map's north-south margins. Make sure the direction of travel arrow on the compass points to north on the map. Rotate map and compass until the magnetic needle of the compass points to the number of degrees the magnetic north is to the right or left of map north.
- 12. Types of CompassesMilitary Lensatic Baseplate Compass Thumb Compass
- 13. Thumb Loop LanyardRing Sighting Slot Lens Luminous Bezel Line Luminous Magnetic Arrow Fixed Index Line Luminous Heading Luminous Sighting Dots Sighting Wire Graduated Straight Edge Floating Dial Bezel LENSATIC COMPASS PARTS and Features of a Lensatic compass PART 1 Basic Land Navigation 1. COVER 2. BASE 3. LENS REAR SITE
- 14. Degrees – common unit of measure is the degree (º). 360 Degrees to a Circle Distance Between Red Marks = 5º Distance Between Big Marks = 10º Distance Between Red Numbers = 20º N = 0º E = 90º S = 180º W = 270º BLACK RING RED RING FLOATING DIAL SCALE Mils - is used mainly in artillery, tank, and mortar gunnery. AND is also used for very accurate azimuth land navigation. 6400 Mils to a Circle Distance Between Small Marks = 20 Mils Distance Between Big Marks = 100 Mils Distance Between Numbers = 200 Mils N = 64 (6400) E = 16 (1600) S = 32 (3200) W = 48 (4800) 8.89 Mils = ½ Degree 17.78 Mils = 1 Degree PART 1 Basic Land Navigation
- 15. SIGHTING A LENSATICCOMPASS PART 1 Basic Land Navigation
- 16. SIGHTING A LENSATICCOMPASS PART 1 Basic Land Navigation
- 17. SIGHTING A LENSATICCOMPASS PART 1 Basic Land Navigation
- 18. SIGHTING A LENSATICCOMPASS PART 1 Basic Land Navigation
- 19. 65° AZIMUTH(11.5m = 1,150mils) SIGHTING A LENSATIC COMPASS PART 1 Basic Land Navigation
- 20. What if Youwanted to hike from the hill 700 west of the hort building to the tower on View Tree Road. What map azimuth do you measure? What would your compass reading be?
- 21. Handout Map Answerin your notebook How far is it on Rt 678 from where Lower Waterloo Rd splits off & remeets 678. What is the 6 digit coord. for the Hort Bdg? What terrain feature is found at 526 905? What terrain feature is found at 553 919? What is the elevation at Fauquier High School? What is the elevation of Fauquier Hospital?
Editor's Notes
- #9 Give the following information to the students to practice this. From GROUND to MAP You target a landmark at MN azimuth 17º to a hill What is the map GN azimuth from your location? Answer ( 26º ) 17º + 9º = 26º From MAP to GROUND With protractor and map, you plot a GN azimuth 112º to a lake What is the ground MN azimuth from your location? Answer ( 103º ) 112º - 9º = 103º
- #14 BEFORE CONTINUING WITH THE SLIDE “ The lensatic compass has 3 PARTS with features on each part.” “ As we go through these PARTS and FEATURES, we will go into more detail on each feature on the next slides. Right now we are just going to go through the names of each item.” CONTINUE WITH THE SLIDE PARTS 1. Cover 2. Base 3. Lens Rear Site FEATURES Luminous Sighting Dots Sighting Wire Etc Read the following ( IN BLUE ) to the students
- #15 AT THE END OF THE RED RING DESCRIPTION Have students look at the compass. Read the following ( IN BLUE ) to the students
- #16 “ Holding the compass to your cheek is very accurate and steady.” “ You sight your target and then read the azimuth.” Read the following ( IN BLUE ) to the students
- #17 “ This is what you see when looking through the lens at the dial. You see the current azimuth reading on the Black Index Line, both in degrees and mils.” Read the following ( IN BLUE ) to the students
- #18 “ As you can see, you can observe both the target and azimuth reading by simply shifting your eye up or down.” “ It is very accurate, fast, and easy compared to an orienteering compass.” Read the following ( IN BLUE ) to the students
- #19 “ Let’s say you want to know what the azimuth heading is to the water tower, so you can calculate your position.” Click to next slide Read the following ( IN BLUE ) to the students
- #20 “ Using the compass-to-cheek method . . . click slide . . . this is what you get.” “ 65 ° azimuth, 1,150 mils.” “ Use this information to calculate your position on the map. This is taught in Part 2 Intermediate Land Navigation.” Read the following ( IN BLUE ) to the students