How to Read a Map
(Topographical Map Reading)
Map reading is an important skill to know and use. The following information is designed to help you understand a Topographical map.
I am going to make an assumption that you can deal with the ordinary street map, but if not, you will find many parallels and similar information on both types.
Some people become intimidated by the topographical map when they see one for the first time. Not to worry, it just has a different focus than the Auto Club type street maps that you are used to.
These are designed to show you the local terrain, or the lay of the land. It will also show you local roads, trails, structures and locations of mines or other man made features.
They are not meant to help you find a particular address in the city. But they will get you around in the wilderness.
If you want to head out into the wilderness this is an essential part of your equipment.
It will show you just about everything you want to know about where you are going and what you will encounter.
It shows roads, trails, buildings, mine locations and just about everything worth recording on the planet.
I will also go into using a compass with a Topographical map because the purpose of this map is to navigate in the wilderness. Doing that without a compass is called getting lost real quickly.
The USGS
The United States Geological Survey (USGS) assumed the role of mapping the entire nation in 1879. The task was immense and so the entire job was not completed until 1992. The program is now called "The National Map".
None of it is done in Metric units. It is all done in Standard English measure so don't worry about having to convert anything.
The Map
The topographical map differs from other maps in that it denotes in detail the contours of the land including the elevations. It details all natural as well as man made features, the buildings, roads and all the changes man has made to the earth.
The map has many uses to an assortment of professions that are in the land use business. This includes large scale architecture firms, earth sciences companies, mining and others. However, we will only deal with the recreational uses for hiking, camping and backpacking.
The first thing you need to do is to find the correct map for where you are going.
There is a catalog found in most camping stores that break them down into sections called the "7.5 minute series" or 1:24,000 scale. Most competent camping stores have them in stock for your general area. Other areas might need to be ordered.
They all have a title describing the particular area that is clearly printed on the top right hand side. (See Figure #1 below for an example). Let's first talk about this simple thing as it is really important to understand.
Fig #1
Things in the Title
The title for this example is "Mount San Antonio Quadrangle". It also shows that this is located in the State of California.
At the bottom of the map it will show you approximately where in the state it is located as well as adjacent map titles. That name is what you will find in the index as you look for the map of your area.
Other Maps
Sometimes everything you are looking for is not entirely on this one section. A road you are following or a trail may end at the edge. In this case you need the next map to complete the information.
There is a notation at the bottom of the map showing you the eight adjoining map titles. See Fig #2 for an example of this.
Your map is the blank section in the center. The eight adjoining map names are shown in the numbered column on the right.
Note right above the boxes there is an outline of the State. There is a small black dot indicating approximately where in the state that map covers.
Fig #2
The 7.5 Minute Series
What does "7.5 Minute" mean? We all know that there is 360 degrees in any circle. That is true about the earth too.
Because one degree covers a lot of ground on the surface of the earth to help locate something it is also divided into 60 parts called "Minutes".
To make it more finite, each minute is further divided into 60 "seconds". Unless you are navigating somewhere with instruments, like a Sextant or today a GPS locater, seconds will not come into any conversation for hiking or backpacking use.
Just for some understanding of the 7.5 minute designation of the map means it covers 7.5 minutes of both Latitude and Longitude. You also find that statement in the title in Figure #1.
This is the best known series and is the only complete one for the National Map.It covers the entire 48 contiguous states, Hawaii, and parts of Alaska. It totals almost 57,000 individual sheets that make up the National Map.
Only Alaska still uses the 15 minute series (1:63,360 or 1 inch to the mile). The 15 minute series was discontinued for the rest of the country years ago.
Along the edges of the map are other numbers. They represent the horizontal and vertical grid used on the planet that we call Latitude and Longitude. This shows the coordinates of this particular place.
You will see one on the top right corner in Figure #1. It says that the top edge of the map is at 34 degrees, 22 minutes and 30 seconds Latitude. The Longitude is just above it.
This too will not come into play for just finding your way around the wilderness unless you are some type of navigator, have a GPS device and understand it all.
Magnetic Declination
Unfortunately, the magnetic lines of force that surround the earth are not all in a straight line. Things within the earth cause these lines of force to shift a bit in some places.
Each map indicates the shift for the area you are in and it is denoted in the lower left hand corner. (See Figure #3)
The center line with star on top represents the true North. However, your compass is always pointing to the Magnetic North as the needle lines up on the local lines of force.
The example shown shows a deviation of 14 degrees to the East, one of the largest shifts found in the continental United States.
To align your map with the true North, you must shift the map 15 degrees to the West.
Fig. #3
Let's do just that...
- Set the map down flat and set your compass on it in the center.
- Align the top of the map with magnetic north.
- Then adjust for the magnetic deviation in your area.
You are now aligned with the actual topography of the area you are in. You should know where you are on the trail so you can see the various features around you and compare them to the map.
Now let's take two bearings with your compass, one to the right and one to left of where you are standing. Do this using some obvious feature or a mountain top.
If you draw two lines from each point on the map using the same bearing they should converge at the point where you are standing.
This serves to improve your map and compass abilities (orienteering) as well as helping you find where you are if you get lost. Of course, by paying attention to where you are going and following the trail map you won't get lost.
Contour Lines
The first symbol we find on a topographical map that we need to describe in detail will be those crazy brown lines running all over the map.
These are called "Contour Lines". (See Figure #4). Their purpose is to show you in detail the "topography" or the actual shape of the land.
On the bottom of the map, just below the scale in Fig #6 it states that the lines represent 40 feet in elevation.
Start with the lines in Figure #4 . You can follow the lines around in a circle. That line is at the exact same elevation all around the mountain.
It is like they sliced straight through the mountain at that height.
You can see the contour of the mountain as it weaves in and out. The next line is either 40 feet higher or lower, depending which direction you are going.
In the center of the smallest circle is the top of the mountain with its name and altitude indicated.
Fig. #4
When the lines get closer together, the path is steeper. As they get farther apart the land is flatter. If they converge into one common line, well get your climbing ropes out or find another path.
Just how high are you at any point?
Along theheavy brown lines you will find the altitude indicated. This is the elevation of that line above sea level.
To find your exact altitude at the moment, just count the lines from a stated altitude to where you are and either add or subtract 40 feet for each one.
Knowing this might make a difference in how well your cooking stoves work or the temperature for that night.
Counting the lines from where you are to where you are going will tell you the altitude gain (or the steepness) you will have along your intended path.
Other Map symbols
When you have any doubt what something means, just look for the symbol key on the page. There are a number of symbols to describe here that will be the most use to you. Most symbols from map to map are just about the same.
Looking at the Map Key again, we see that there are symbols for different types of roads from highways to 4 X 4 tracks only. The dotted line indicates a hiking trail and THAT is most likely where you will be!
You can find the trailhead from where it intersects the road. The twists and turns, or the path of the trail is usually pretty accurate. Sometimes because of washouts, or other natural causes, trails have been relocated a bit in some sections.
When you check in with the local Rangers they will be able to tell you about the trail condition you choose to follow. It's a good bet that they were the ones that repaired it. If you find things out of sort, please be kind and report it when you return.
Major trails, such as the Pacific Crest National Scenic Trail are indicated as in Fig #5.
The Pacific trail is continuous from Mexico to Canada and travels through some really great areas.
Most people hike it in sections over several years by starting on one end and coming off at a predetermined place where it crosses a major road and have someone pick them up. They come back at a later time to where they ended the last section and take off again into the wilderness to the next chosen spot.
Fig. #5
Doing this for say one week at a time will take a long while to do the entire trail, but there are not a lot of people around who can sport a Pacific Crest Trail "Brag Rag".
Any man made structure be it a house, cabin, out building etc. is always indicated by a black dot. If it comprises a community, its name will also be shown.
As in all maps, water is typically shown in blue, forested areas in green and desert or brush areas in tan or light brown. This is all pretty standard.
Once you understand a few things about these maps I think you will agree that it's not really that hard.
Map Scale
As I had previously stated the scale of the map is 1:24,000. So what does that mean to you about the distance to where you are going?
The map scale noted in Figure #6 gives you the distance in Miles, Feet and also Metric measurements, if you need that too.
One trick you should know is how to find the distance along a twisting trail or road. It is to lay a string along the path and then straighten it out on the scale to find the straight line distance.
I carry dental floss in the field with me and that works great.
Fig #6
Other Trail Map Information
You will not find detailed information for a specific trail on a USGS Topographical map.
However, there are other maps found in the same stores where this one is found that specialize in hiking trails in your area. Some also will come with small books that give a great deal of information about the area, the specific trail you are interested in and the camping sites.
The map alone can contain a lot of good information about where you are going. If you can understand the basics of a USGS Topographical map, you can read a commercial trail map with ease.
The commercial trail maps are frequently a larger scale, cover a smaller area and are a little easier to read. They utilize most of the same data (guess where they got it all from?) that you will find on the USGS map. That will include the contour line information.
They also cost a bit more than what the government charges but they will serve you well on the trail.
I tend to use both in planning a trip over any trail. They each provide good information that I fine useful. I usually bring one of them with me and give the other to one of the party members to carry.
Well, now that you are a sophisticated map reader get going on planning that next hike or backpack. Plan well and have a great time!!