ey are representing an overhanging cliff in which case those beneath the overhang are dotted. On a vertical cliff several contour lines may become superimposed. 4. Contour lines never divide. 5. Contours are far apart on a gentle slope.
52 CONTOUR LINE RULES 6. Contours are close together on a steep slope. 7. Contours bend upstream in valleys and cross streams at right angles. 8. On level ground there are no contours. 9. An isolated closed contour has the same elevation as the next adjacent contour. 10. All points inside a depression contour are lower than the line.
53 CARDINAL DIRECTIONS The four cardinal directions on a map are: North (at top of map) South (at bottom of map) East (at right of map) West (at left of map)
54 THE MAGNETIC COMPASS The magnetic compass is an important aid for: Taking bearings Map orientation Position location Triangulation Route finding, etc.
55 THE MAGNETIC COMPASS The magnetic compass works on the principle that the pivoting magnetized needle, will always point to the magnetic north. There are a variety of compasses available, ranging in price from a few dollars to hundreds of dollars.
56 PARTS OF A COMPASS 1. MAGNETIC NEEDLE: Points consistently towards the north magnetic pole. All measurements with the compass are therefore made relative to the magnetic north direction.
57 PARTS OF A COMPASS 2. COMPASS HOUSING AND GRADUATED DIAL: The compass housing is a sealed capsule which contains the magnetic needle. It is filled with a light oil so the needle comes quickly to rest. The outer ring of the housing is graduated in degrees from 0 to 360 in steps of 2 degrees. The north direction is indicated by the set of parallel (meridian) lines on the transparent base plate. The large black arrow which is also on the base plate can be rotated independently by means of a small screw in the graduated metal dial.
58 PARTS OF A COMPASS 3. BASE PLATE AND DIRECTION ARROW: Used in the bush to point out or obtain bearings. Used on a map to measure or plot bearings. Note that some compasses have sighting mirrors to aid in obtaining bearings in the field.
59 FACTORS AFFECTING COMPASS OPERATION The compass needle is magnetic and will be attracted toward any large iron or steel object or it will respond to local magnetic fields. If you are near a car, snowmobile, ATV, or outboard motor, especially if they are running, the needle may be way off. Radios, GPS units, knives, axes, clipboards and even metal belt buckles will affect the operation of the compass. If you are unsure of how far the local magnetic attraction of an object extends, simply move away from the object while watching the compass needle. When it no longer wavers towards the object, the compass is set for operation.
60 BEARINGS Bearings are angular measurements with respect to the position of the observer, and the position of a distant object or intended destination course. Bearings may be expressed in terms of: Azimuths (used by Nova Scotia SAR teams) Quadrants (not used by Nova Scotia SAR teams)
61 AZIMUTHS BEARINGS Azimuths are bearings, expressed as angles, measured clockwise from north throughout the full range of the directional circle. Azimuths range from 0 o 360 o.
62 MAGNETIC DECLINATION There are three primary references that are used to indicate direction: Magnetic North (on compass) the direction to the earth s north magnetic pole. This is where all compass needles point. True North (on globe) the direction to the earth s north geographic pole. All lines of longitude meet there. Grid North (on map) the direction indicated by the N-S lines on the grid which overlies the map. Grid north is slightly different than true north. Since this difference is so little, for GSAR purposes, grid north and true north are the same.
63 MAGNETIC DECLINATION The angular difference between true north and magnetic north is called Magnetic Declination. All topographic maps display a declination diagram. Depending on your location, declination will be either East or West. In Nova Scotia declination is West.
64 MAGNETIC DECLINATION Example of a Map s Declinatio