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Beginner Map Reading Compass

Beginner Map Reading Compass. Compass. Parts of a Compass. Compass. Instrument used to show direction Points to the Magnetic North Pole Maps are generally printed with north up USGS topographic maps show GN, MN and H GN is Grid North – the north of the map grid

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Beginner Map Reading Compass

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  1. Beginner Map ReadingCompass

  2. Compass

  3. Parts of a Compass

  4. Compass • Instrument used to show direction • Points to the Magnetic North Pole • Maps are generally printed with north up • USGS topographic maps show GN, MN and H • GN is Grid North – the north of the map grid • MN is Magnetic North – where the compass points • H is True North – geographic north, the northern end of the north-south axis of the Earth • The difference between True North and Magnetic North is magnetic declination • Declination changes with time as indicated on the map, but the rate of change is not constant

  5. Position of the Magnetic North Pole in different years

  6. Find this on your map MN TN

  7. Declination MN vs. TN On the day the map was printed

  8. Declination • What is the declination on your map? • Current magnetic declination near Crested Butte is • 10° 20’ E, changing by 0° 7’ West per year • Declination is important when converting between map (true or grid) and compass (magnetic) azimuths • Azimuth is the angle measured from north in a clockwise direction (0° north, 90 ° east, 180° south, 270° west)

  9. Declination10o 20’ E As of July 1, 2009 From Crested Butte

  10. We will round off to 10 for this presentation Please copy the formulas

  11. Using Compass and Maps • Understanding how to use declination • Using a map and compass to find your location • Although it’s not the perfect terminology, we will use the words bearing and azimuth interchangeably in this presentation

  12. I drew a line from my home in CB So. to the top of Round Mt • I measured the angle using a protractor = 150o

  13. I then lined up my compass with Round Mt and read the compass • It showed 160o • I plotted the 160o on the map and the result is shown here • The difference in the two lines is the declination • If I traveled using 150o without adjusting for D. I’d miss by ½ mile

  14. Calculate the Magnetic Baring • Use the formula to calculate the Magnetic Baring we should enter on the compass • Once we calculate the MB of 140o we look at 140o and see it’s lined up with the top of Round Mt • The 140o was drawn on this map to show you what a TN plot of 140 would look line

  15. If the declination was W, you would use this formula

  16. End of Compass Section 3 - A Next section Section continues with 3 – B

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