Nearly ever day, you do land navigation without even realizing it. When you drive your car, you use known land features (street signs) to get where you are going. When you use a road atlas to determine your course for a long road trip, you’re performing land navigation. While not necessary, a map can play a vital role in land navigation. But you need to learn how to read a map before you can properly use it to navigate.
If I can teach you one thing, let it be proper map maintenance. You can’t fathom how important it is to keep your map properly folded and clean until you’re trying to read what the map says underneath a mud stain. The best thing you can do is keep the map folded and in a ziploc bag unless you need to use it. There is a lot of detail in some maps, especially topographical maps, and the tiniest discoloration or marking can really ruin your day. If you get something on your map, try to get it off as quickly as possible.
There are several different types of maps. Physical maps show general physical features such as mountains, desert, water, etc. Political maps show the boundaries between political entities. Road maps, as you would expect, shows roads. Resource maps show economic or natural resources represented by small icons. Climate maps use color coding to indicate the climate in an area. Topographical maps are highly detailed local terrain maps. Essentially, most of the maps I described are totally useless for land navigation. Road maps are only useful if you’re following a road (which is a legitimate strategy), physical maps are only good for getting a general idea of where you are, and resource, political, and climate maps may not even be drawn accurately to scale.
Every map has the same features that you should be aware of. First of all, the top of every map is always North. Why is the top always north? Unfortunately, the answer to the has been relegated to the past so all I can say is that it’s that way because it has always been that way. There is usually a compass rose (indicating cardinal directions) and a legend. The legend is key because it defines the symbols used and what they represent, which can vary from map to map. The color blue is typically reserved to represent water, so if you see blue on a map its probably water.
Given the choice of maps, you should always go for a topographical map. These maps are highly detailed terrain maps and are updated fairly often (often enough that they are usually dated). For that matter, there is a ton of information written in the margins of topographical maps. The state and county that the map is in is usually displayed in the upper right hand corner. In the lower right hand corner is information about roads within the area of the map and a picture depicting where the map is in relation to the state it is in. The area that the map represents is called a “quadrangle” and is designated a name or label by the United States Geological Survey. Each adjacent quadrangle is labelled in the margin of each topographical map. This is convenient if you need to plot things out on more than one map.
Colors play an important part in the topographical map, they define features in a way that is easily discernible from each other.
- Brown lines show the terrain contour and are called “contour lines”. They show the shape of terrain and the elevation.
- Black lines indicate man made features like roads, trails, etc.
- Blue, as you would expected, indicates water features.
- Green is used to show vegetation.
- Red is used for highways and land grids.
Because topographical maps are so detailed, a specific set of symbols was developed to represent a great deal of information in the smallest amount of space possible.
When referring to maps (especially topographical maps) there are some terms that will crop up from time to time that you need to know.
- contour lines – On a topographical map, each contour line represents a specific elevation. It is called a contour line because when placed all together they show the contour of the terrain feature.
- contour interval – The contour interval is the space between each contour line. The interval is a uniform change in elevation. This means that contour lines can be space close or far depending on the change in elevation in the area.
- index contour – Index contour lines are the contour lines that represent the base elevations. For instance, the index contours on one map may be every 100 feet, or every 1000 feet.
- ridge – A ridge is a relief feature that is a series of hills in a chain. This feature looks similar to the knuckles on the top of your hand when closed into a fist.
- hill – A hill is a feature that rises up from the surrounding terrain. Each of the knuckles on your hand look like a hill.
- saddle – A saddle is the depression between a pair of hills. This is represented on your hand as the space between your knuckles.
- valley – A valley is a depression in the surrounding terrain that usually extends in one particular direction. On your hand, this is represented as the space in between your fingers when they are extended.
- depression – A depression is an area that is sunken in from the surrounding terrain. If you cup your hand, palm up, it forms a depression.
- spur – A spur is a minor ridge that extends from a larger ridge. If you look at your fist, the tops of your fingers are the spurs to your knuckles.
- draw – A draw is essentially a valley formed in between two ridges. If you make a fist with your hand, you form a draw in between your fingers.
- cliff – A cliff is a sudden drop off in elevation, think the side of your hand.