Quick Answer
To use contour lines for terrain navigation with a compass, identify the slope and direction of the terrain by analyzing the contour interval and line density, then use the compass to orient the map and determine the direction of travel. Contour lines help identify potential obstacles and hazards. Adjust for declination to ensure accurate readings.
Understanding Contour Lines
Contour lines are a critical component of topographic maps, representing the shape and elevation of the terrain. A contour interval of 20 feet or less indicates a highly detailed map, while 40 feet or more indicates a less detailed map. Contour lines with a density of 1-2 lines per 100 feet indicate gentle slopes, while 3-4 lines per 100 feet indicate steeper slopes.
Interpreting Contour Lines for Navigation
To use contour lines for navigation, identify the slope and direction of the terrain by analyzing the contour interval and line density. A contour line with a density of 4-6 lines per 100 feet indicates a steep slope, while a line with no lines per 100 feet indicates a flat or level area. Use the compass to orient the map and determine the direction of travel, taking into account any obstacles or hazards identified by the contour lines.
Adjusting for Declination
To ensure accurate readings, adjust the compass for declination, which is the difference between magnetic north and true north. In the United States, declination ranges from 0-20 degrees, depending on the location. Using a declination map or online resource, determine the declination for your location and adjust the compass accordingly, typically by rotating the bezel 0-20 degrees.
Find more answers
Browse the full Q&A library by topic, or jump back to the topic this question belongs to.