![]() ![]() Slope is the change in elevation over a given horizontal distance. You can tell the slope of the terrain by analysing the spacing. #3: Interpret the Distance Between Contour LinesĬontour lines may be evenly or unevenly spaced close together or far apart. Either way, the units of measurement is usually stated in the legend. Some are in feet while others are in metres. Note: Different topographic maps use different units of measurements. If the numbers associated with the contour lines are decreasing, there is a decrease in elevation. If the numbers on the contour lines increase in value, the elevation of the terrain is rising. The video below explains how to compute the contour interval. In other words, the difference in elevation between one contour and the next one is 20 metres. In the above image, the vertical interval (V.I.) is 20 metres. The difference in associated numbers is the contour interval. In the absence of a legend, pick two contour lines that are next to each other. Extracted from Kenya topo map (scale 1:50,000) Sometimes, the interval is stated in the legend, as shown below. It is usually constant throughout the map. #2: Determine the Contour IntervalĬontour interval is the difference in elevation between one contour and the next. You can determine their elevation by counting up or down from the nearest index contour line and multiplying by the contour interval (more about how to do this in the next step). Often, major contours occur in intervals of five or ten contour lines.Īt the same time, other contour lines are lighter, thinner and have no label. These are called index or major contours. ![]() On most topographic maps, you’ll notice that some contour lines are darker brown, thicker, and labelled with the elevation. They allow you to read the shape of the Earth’s surface How to Read Contour Lines #1: Identify the Contour Lines ![]() buildings, trees, roads, etc, aren’t captured by contour lines.Ĭontour lines are important because they make it possible to represent the Earth’s 3-dimensional physical features on a 2-dimensional topographic map. This means that the height of objects, e.g. The most important thing to remember about contours lines is they represent the natural terrain or bare earth. They appear as squiggly lines with numbers as labels, drawn in shades of brown. How do you identify contour lines on a topographic map? Examples include roads, hills, rivers, hospitals, towns, forests, lakes, power lines, administrative boundaries, etc. The focus of this post, however, is on contour lines found on topographic maps.Ī topographic map accurately represents the physical features of an area at a specific scale. Note: Meteorology (isopleth), magnetism (isogon) and even drive-time (isochrones) also use contours for different purposes. The elevation represented by contour lines is the vertical distance above or below sea level. For example, if you were to hike along a contour line, you would remain at the same elevation the whole way, never travelling up or down. Let’s start by answering an important question: What Are Contour Lines?Ĭontour lines are lines drawn on a topographic map that join points at the same elevation. This post will explain how to read contour lines and outline 8 things to remember if you’re new to contour lines. Just a few things to take note of, and you’re good to go. Making sense of contour lines doesn’t have to be complicated. Knowing how to read contour lines comes in handy when choosing hiking, or backpacking routes, managing hazards such as flooding, selecting where to build infrastructure, to name a few. Regardless of your profession, vocation, job,… knowing how to interpret contour lines is a skill you should have.īy studying contour lines, you can learn a lot about the surrounding terrain: height of hills, depth of valleys and steepness of climbs. ![]()
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