Navigation Continued Contour Lines Contour lines represent elevation

Navigation Continued

Contour Lines Contour lines represent elevation above sea level and can be used to show slop incline They connect points of the same elevation and are continuous, forming a closed loop E. g. peaks are represented by a series of closed lops E. g. in other instances the contour lines close on themselves only after circling an entire mountain range

Contour Interval Contour interval refers to the change in elevation between two contour lines E. g. a contour interval of 40 meters means that the elevation difference between two contour lines on the map is 40 meters in the field On some maps the contour interval shifts from a 20 meter interval below 2000 meters to a 40 meter interval above 2000 meters

Slope Steepness If contour lines are closer together, more elevation change is represented in the same distance, thus the incline of the terrain is steeper In Illustration 1, the contour lines on the map are closely spaced near Point IV, showing very steep slopes/cliffs In comparison, below tree line in the valley bottom, at Point II, the slopes are low in angle with widely spaced contour lines

Is it up or down? On many map sheets for mountainous regions, it is possible to distinguish elevated regions by looking for the alpine zones or areas above tree line These zones are represented as white area In contrast, the forested regions are shown in green

Up or Down Reference contours can also be used to assist in differentiating peaks from valleys, they are often darker, have the elevation printed on the line, often found every 5 th contour Note the series of reference contours from 6500 ft. In the valley bottom to 8000 ft near the peak at Point III

Up or Down Finally, by carefully examining water drainage, it is often possible to identify up from down The river at Point I flows down into the valley to the north The lake in the bottom right corner of the map, drains NW (up and left) showing a downward slope in that direction

Large Terrain Features such as peaks, ridges, passes and valleys can be identified once familiar with the basic topography of the map Peaks are often named, but if not, look for closed loops that decrease in size Peaks can be relatively broad, with widely spaced contour lines near the top as shown by Point VIII Sharp summits are shown with closely spaced contours and a tiny loop at the top, Point III

Large Terrain From most peaks you can trace ridges that radiate out from the top, forming ‘V’s’ that point towards lower elevations Point IX shows a broad pass to the southeast of Peak VIII Valleys can be identified by ‘V’s or ‘U’s in the contour line that point upstream, opposite to the ridges above Point VI shows a flat valley bottom with Ushaped contour lines Point VII shows a narrow valley with Vshaped contour lines that point uphill