Off-Road Emergency Welding

Diving for Spiny Lobster

December 23, 2014 Comments (0) Field Craft

Learn How To Navigate With Topographic Maps

There are many different ways to navigate the earth, both technically and physically. With the new advances in technology, it’s easy to become too dependent on GPS to tell us where we are and where we are going at all times. While map reading can be incredibly technical, we want to touch base on the most basic type of map reading: terrain features. This will help lay down the foundation for your future learning in map reading.

Map reading is an art and is definitely a perishable skill.

Topographic Map with Contour Lines Example

An example of a topographic map with contour lines in brown. Image courtesy of the U.S. Geological Survey.

Before we get into the more specific features of maps, let’s first define what a map is. A map is a graphic representation of a portion of the earth’s surface drawn to scale, as seen from above. A topographical map features large-scale detail and uses symbols and numbers to show natural and man-made features.

Since the topographical maps we are talking about are one dimensional, they have a different way of showing elevations and depressions in the earth. On maps, the earth’s three dimensional features are represented with contour lines that share the same center, or are concentric. They look like straight and/or curvy circular lines that share the same center on a map. These concentric circles are used to show how steep, narrow, gradual and wide the terrain is. The closer together the lines are to each other, the steeper the terrain is.

Terrain features are split into three different groups: major, minor and supplementary. Let’s take a look at how to identify of each of them on a map.

Five Major Terrain Features:

  • Hills
  • Valleys
  • Ridges
  • Saddles
  • Depressions

I was taught to remember these five major terrain features by using the phrase “Hidden Valley Ranch Salad Dressing.” After reciting this phrase, it stuck with me almost immediately. I suggest you try it out.

Hill Contour Lines Topographic Map

Hills

On a map, a hill is represented with a series of concentric lines that look like a bulls-eye. Depending on the steepness of the hill, these lines will either be far apart or close together. The greater the distance between these lines, the less steep the slope.

Saddle Contour Lines on Topographic Map

Saddles

A saddle is the low ground that connects two hills together. Together, the saddle and hills create a ridge line. On a topographical map, a ridge line will have very few lines of elevation and will show at least two hills with a saddle in between. The saddle is the empty white space between the two hills in the image above.

Valley Contour Lines on Topographic Map

Valleys

Valleys are usually pretty easy to spot because they frequently feature a blue line in the middle of them, depending on the region. This blue line indicates water running through a valley. Just remember, a valley runs straight through two elevated pieces of terrain.

Depression Contour Lines on Topographic Map

 

Depressions

The last of the major terrain features is a depression. Besides hills, depressions are the easiest features to identify. They are shown as two circles with contour lines close to each other. You should see tick marks in between the lines pointing towards the low ground.

Three Minor Terrain Features:

  • Cliffs
  • Draws
  • Spurs

Cliff Contour Lines on Topographic Map

Cliffs

Of the three minor terrain features, cliffs are the easiest to identify on a topological map. When looking for a cliff on a map, look for multiple contour lines merging into one line. The last contour line with ticks on it facing towards the ground is a cliff.

Draw Contour Lines on Topographic Map

Draws

Draws represent land in which water has modified the slope. Imagine standing on a gentle slope looking uphill. As the ground slopes upward, it fans out in three directions, while downhill it merges into one depression where you are standing. This is a draw. A draw’s unique shape is caused by water converging from several directions uphill, down into one downhill depression.

On a topographic map, draws are shown with U-shaped or V-shaped contour lines. These lines point to high ground.

Spur Contour Lines on Topographic Map

Spurs

Like draws, a spur is terrain that has been modified by water. A spur is long ground that gently slopes from a hill to lower ground. On a topographic map, spurs look like a series of inverted U- or V-shapes on a ridge. These shapes should be pointing away from high ground. You can see how water would course down the ridge and form the “V” shaped grooves over time.

Two Supplementary Terrain Features:

  • Cuts
  • Fills

The supplementary features, cut and fill, represent man-made modifications to the land.

Cut and Fill Contour Lines on Topographic Map

Cuts

A cut is a raised portion of land that has been cleared and flattened by humans. Cuts are usually created to form a flat pathway for transportation.

Cuts are generally only shown on a map when they are at least 10 feet high. On a topographic map, cuts are shown with a contour line that extends the length of the cut and feature tick marks that go along the cut line to the road bed. These ticks are drawn inside the cut contour lines.

Fills

Fills are similar man-made alterations.  Instead of flattening land, fills represent when material has been used to fill a depression to form a level site for a road.

Again, fills are only shown on maps when they are at least 10 feet high. Like cuts, they are shown with contour lines that feature tick marks. For fills, however, the tick lines point towards the lower ground and are drawn outside of the contour lines.

Map reading is an art and is definitely a perishable skill. Before any serious hike, trail walk or expedition, do some map reconnaissance so you know what to expect before you arrive. This will help you better understand the terrain and prepare you for situations when you can’t use electronics.

Try and plan a primary and alternate route for your trips just in case a trail or route gets washed out and isn’t passable. We can’t always depend on our GPS, and inevitably, Murphy will arrive and ruin everything. Plus, you will feel a sense of accomplishment when you navigate to your camp site using just a topographical map.

Stay safe and live wildly.

Things can seem tremendous the first period one goes to order spy apps for mobile phone. What aspects families think when they are going to use how to catch a cheating husband? Here we discussed at some key matters to keep in view, as well as how you can find options to start. What is the most momentous data you must know about catch a cheating spouse? Probably every adult knows about “how to catch your boyfriend cheating“. Sure, before you go and purchase the spyware, you must know a little bit about the provider. However, you have to understand one fact that there are wide ranges of spyware are available depending upon your needs. Absolutely, we cannot deny the fact that price is not always a perfect indicator of quality. Thankfully, any good producer mostly will allow you to upgrade a sofware later on if required, so don’t feel as though you need to start off on a plan that costs more than you need.

Leave a Reply

Your email address will not be published. Required fields are marked *

%d bloggers like this: