Orient map with compass
3a.
Demonstrate how a compass works and how to orient a map. Use a map to point out and tell the meaning of five map symbols.
A map gives you a bird’s-eye view of terrain, waterways, elevation, and trails. A compass tells you which direction you are facing relative to the Earth’s magnetic field. By combining the two, you can navigate anywhere in the backcountry with confidence.
Anatomy of a Baseplate Compass
A standard orienteering baseplate compass consists of several essential parts:
- Baseplate: The clear plastic plate you place flat on a map, featuring straight edges and rulers.
- Direction-of-Travel Arrow: The fixed arrow on the baseplate pointing forward, showing the path you will walk.
- Rotating Compass Housing (Bezel): The circular dial marked with the 360 degrees of a circle and the cardinal points (N, E, S, W).
- Magnetic Needle: The freely spinning needle in the housing. The red end points toward Magnetic North.
- Orienting Arrow (“The Shed”): The red arrow outline fixed inside the base of the housing.
- Orienting Lines: The parallel lines inside the housing used to align with the north-south grid lines on a map.
- Index Pointer / Line: The small mark at the front of the housing where you read the numerical bearing.
- Scales / Rulers: Inch and millimeter markings, or fractional map scales (such as 1:24,000) for measuring ground distances.
How to Orient a Map Using a Compass
Orienting a map means aligning the north on the map with actual North on the ground. Once oriented, every feature on your map aligns directly with the physical world around you.
- Find True North on the Map: Look for the north arrow or the vertical grid lines on the map.
- Set the Compass to North: Rotate the compass housing dial until 0° / 360° (N) aligns with the index pointer.
- Position Compass on the Map: Lay the map on level ground. Place the compass on the map so that its long edge runs parallel to a north-south line (or the map’s side border), with the direction-of-travel arrow pointing toward the top of the map.
- Account for Magnetic Declination:
- The Earth’s magnetic north pole differs slightly from True (geographic) North.
- Check the declination diagram at the bottom margin of your USGS map. If declination is 10° East, adjust your bezel or align with the magnetic north line.
- Rotate Map and Compass Together: Turn the map and compass together until the red magnetic needle rests snugly inside the red orienting arrow outline (“Red in the Shed”).
- Verify Terrain: Look up. If the map shows a mountain peak to your northwest, that peak will be directly northwest in the real landscape.
Identifying Topographic Map Symbols
United States Geological Survey (USGS) topographic maps use standardized colors and symbols to represent landforms, water, and human structures:
| Color / Symbol | What It Represents | Examples & Field Meaning |
|---|---|---|
| Brown (Contour Lines) | Elevation and Land Shape | Lines connecting points of equal elevation. Lines close together indicate steep cliffs/slopes; lines far apart indicate gentle slopes or flat plains. “V”-shaped contours pointing uphill indicate a stream valley or ravine. |
| Blue (Water Features) | Water and Wetlands | Solid blue indicates perennial lakes, ponds, and rivers; dashed blue lines indicate intermittent streams (dry part of the year); blue with grass tufts indicates marshes and swamps. |
| Green (Vegetation) | Tree Cover & Woodlands | Heavy green shading indicates forests, woods, and orchards. White areas represent open meadows, clearings, or bare rock. |
| Black (Manmade Features) | Cultural & Survey Marks | Black dashed lines indicate hiking trails; solid/parallel lines indicate roads and railroads; small black squares indicate buildings; a cross represents a church, and a flag indicates a school; “BM” marks an elevation benchmark. |
| Red / Pink (Urban & Roads) | Built-Up Areas & Highways | Red lines mark primary highways and major roads; pink shading indicates densely populated cities and urban areas. |
Brown (Contour Lines)
- What It Represents
- Elevation and Land Shape
- Examples & Field Meaning
- Lines connecting points of equal elevation. Lines close together indicate steep cliffs/slopes; lines far apart indicate gentle slopes or flat plains. “V”-shaped contours pointing uphill indicate a stream valley or ravine.
Blue (Water Features)
- What It Represents
- Water and Wetlands
- Examples & Field Meaning
- Solid blue indicates perennial lakes, ponds, and rivers; dashed blue lines indicate intermittent streams (dry part of the year); blue with grass tufts indicates marshes and swamps.
Green (Vegetation)
- What It Represents
- Tree Cover & Woodlands
- Examples & Field Meaning
- Heavy green shading indicates forests, woods, and orchards. White areas represent open meadows, clearings, or bare rock.
Black (Manmade Features)
- What It Represents
- Cultural & Survey Marks
- Examples & Field Meaning
- Black dashed lines indicate hiking trails; solid/parallel lines indicate roads and railroads; small black squares indicate buildings; a cross represents a church, and a flag indicates a school; “BM” marks an elevation benchmark.
Red / Pink (Urban & Roads)
- What It Represents
- Built-Up Areas & Highways
- Examples & Field Meaning
- Red lines mark primary highways and major roads; pink shading indicates densely populated cities and urban areas.