Map reading, sometimes spelled as map-reading, is the skill of interpreting the geographic information presented on a map. By developing this skill, you can develop a mental image of real-world locations by analyzing the symbols and data depicted. Successfully reading a map requires understanding essential details like distance, direction, natural and man-made features, and topographical elements.
For those familiar with geography, reading a map might feel second nature. However, if you’re new to map reading, simply opening a map and figuring out how to find and interpret the information can be challenging. Maps are designed according to certain standards, and understanding these standards is crucial for effective map reading.
To begin, maps provide two types of location information: relative and absolute. Relative locations indicate where something is in relation to another reference point, requiring you to have two pieces of information. For instance, if someone tells you a place is five miles north of Main Street, you’ll first need to find Main Street and then identify the area five miles north of it. Absolute locations, on the other hand, provide an exact position. If you’re given specific coordinates, you can pinpoint the location directly by following those coordinates on the map.
Step by step instructions to learn how to read a map
To understand how to read a map, we are going to examine different types of maps, including this example of a USGS topo map. A USGS topo map, short for United States Geological Survey topographic map, is a detailed and highly accurate representation of the natural and human-made features on the Earth’s surface.
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USGS topo maps are specifically created to cover the entire United States. USGS topographic maps, or US topo maps, are organized into a grid system that divides the United States into a series of map sheets. Each sheet covers a specific area of the country, and the maps are available at various scales depending on the level of detail required.
As indicated by their name, topo maps are designed to show the terrain’s topography, or the arrangement of the land’s physical features. This is done using contour lines, which indicate elevation changes and give a sense of the landscape’s three-dimensional form.
In addition to topographic details, USGS topo maps include other critical information such as roads, water bodies like rivers and lakes, vegetation, and man-made structures. They also display a grid system, often based on latitude and longitude, which allows for precise location referencing.
These maps are common tools for activities like hiking, planning, land management, and scientific research, as they provide a comprehensive view of both natural and built environments. Understanding how to read a USGS topo map is a fundamental skill for anyone who needs to navigate or understand the layout of the land in detail.
USGS top map of Yosemite
The USGS topo map we will look at is the 1:24,000 scale Half-Dome map which covers a portion of Yosemite National Park.
Now that we have our example map, let’s get started on learning how to read this USGS topo map.
Map Title
Just like the title of a book, the map title will give you a clue as to what the intent of the map is. Map titles can be found in many places on a map. The font size of a map title is typically very large as to draw the viewer’s attention.
Map title for a USGS topo map
In our example map for Yosemite, the map title is found at the top of the map:
The title section for this type of map from the USGS is a little different than most maps you will find. The title is actually split across the top of the page. The title section to the left of the image is the title for the map series: US Topo.
US Topo is a map series that the USGS creates showing topography in sections known as quadrangles for the entire United States. To the right of the above image is the title for this particular quadrangle: Half-Dome. Next is the state the quadrangle covers: California. Last is the map scale for the quadrangle: 1:24,000.
Map title for an 18th century map
On other maps, the title of the map will be more obvious and descriptively titled. Take, for example. this 1777 map of New York and New Jersey. The title section of the map has been enlarged for view ability. The title is quite description. By reading the title, the reader can understand the geographic focus of the map as well as well the source information is from that was used to create the map.
Locator Map
A locator map, also referred to as an inset map. is a smaller map that shows the relative location of the geographic area mapped to a larger area.
Inset map for Texas showing its relative location in the United States
For example, this map of Texas has a locator map that shows the relative location of Texas (shaded red) to the rest of the continent United States.
Locator map on a US top map
Referring back to our example Half-Dome topo map, this locator map shows the relative location of the quadrangle (red square) to the rest of the state of California.
Underneath the locator map is an index map which can be found on maps that are part of a map series or an atlas. The point of the index map is to show the location and names of the surrounding quadrangles to the Half-Dome map. This is useful if you are looking for the topo map that is just out of the range of the current topo map you have.
Grid lines on a map
Once you have the basics of how a given map is laid out, scaled, and illustrated, it’s time to look at the borders of the map. Some maps are laid out in a grid pattern based on latitude and longitude. These grids are known as graticules. Latitude and longitude are imaginary lines that bisect the earth- latitude runs north and south, while longitude goes around east and west.
Other maps, especially those of smaller areas, may have their own letter and number designations for their grid. If you are given a location’s latitude and longitude, or grid coordinates, then finding it is easy. All you need to do is locate the relevant north-south line, then travel along it until you hit the relevant east-west line. The location you’re looking for will be where the two lines bisect. Not all locations will fall exactly where two lines cross, but knowing the general coordinates of an area can be useful for narrowing down where you need to look.
Interpreting the map legend
Since maps are representations of the real world, cartographers will use symbols and colors to indicate to the reader what they are mapping.
Understanding the Symbols on the Map
What the symbols on the map mean are defined in what’s known as the map legend or the map key.
The point of a map legend is to describe what all symbols on the map mean. Maps with a complete map legend or key can be used without the need for additional interpretation guides.
The map below shows the General Plan land use zones for the City of Santa Clarita in California, the map in the lower right corner lets the reader understand the meaning of the different colored areas.
By matching the color to the match legend, users can understand that zones shaded red are industrial, blue shades are industrial, and yellows are non-urban residential.
USGS Topographic Symbols guide
The US Topo maps can contain a lot of symbology that isn’t defined on each individual quadrangle. If you look for the map legend on our example Half-Dome quadrangle map, you will notice the legend is very sparse:
If you look at a small section of the Half-Dome map, you will see that there are a lot of symbols that are not included in the very small legend on the USGS map. There simply isn’t enough room to include all the symbology on these very detailed maps.
To understand what those symbols mean, you would need to reference the USGS Topographic Symbols guide to look them up.
Some symbols are meant to be intuitive. For example, the green symbol with the picnic table lets you immediately understand this point on the map is a rest area where you could stop to eat food. The light brown symbol with the hiker lets you know that path is a hiking trail.
There are other symbols that are harder to understand which is where the USGS Topographic Symbols guide comes in handy. For example, we can see areas that look like this:
So what do the blue symbols mean? If we look in the symbol guide, we learn what those symbols mean by looking for a matching symbol:
Map Orientation
The second thing you need to do to read a map is determine its orientation. North, south, east, and west are the four cardinal directions, and most maps (but certainly not all) will be oriented with north (meaning “true” north, as opposed to magnetic north) at the topmost portion of the map, south (“true” south) at the bottommost, east to the right, and west to the left.
Many maps have a compass rose or north arrow on it that tells you how it is oriented, so you won’t need to worry about having to assume that north is up. A lot of maps are oriented so that north is towards the top of the map. When a map is oriented with the map towards the north, the north arrow will indicate that North is directly up:
In the Half-Dome map example, the USGS puts more technical information to show both the direction of geographic north (GN) and magnetic north (MN):
Not all maps are oriented with north at the top of the map. For example, maps in the Middle Ages were frequently oriented with east towards the top.
For a more current example, let’s take a look at the city of Santa Monica in California. This beach town sits along the coast of the Pacific Ocean.
For readability and aesthetics, cartographers at the city rotate maps 46 degrees so that the beach side lines up along the bottom of the page. In this map of the city streets, notice that the north arrow in the lower left hand corner is tilted to show the direct of due north.
Related: To North Arrow or Not to North Arrow
Understanding Map Scale
Map scale is a way for cartographers to let the reader know how to translates distance on the map to distance on the ground. Map scale is a expression of the ratio of a distance on the map to the distance in the real world.
For example, the Half-Dome map has a scale of 1:24,000. This ratio means that every one unit on the map is equal to 24,000 of the same units on the ground. This type of map scale is known as Representative Fraction (RF).
Therefore, 1 inch on the map is equal to 24,000 inches on the ground.
Map scale can also be expressed as a ratio of one type of unit to another type of unit. You might see a map scale expressed as 1″ = 100′. That means that one inch on the map is equal to 100 feet in the real world. This type of map scape is known as a Verbal Scale.
A third option for map scale is to show the relationship of the map to the real world as a bar scale. A bar scale is essentially a ruler on the map. Distance on the map is expressed as a graphic and the corresponding distance is noted on the bar scale.
This example from the Half-Dome map shows both a RF and has a few map scales:
Video: large scaled versus small scale maps
You can learn more about map scale by reading the Map Scale article or by watching this video: Understanding Map Scale: Large Scale Versus Small Scale Maps
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The last important piece of information to understand about map reading is the metadata.
Metadata is data about the map. Typical pieces of metadata that you might find on a map are the name of the cartographer, the date the map was created, the source and dates of the data used to create the map, the map projection and datum used, and any disclaimers the creator of the map wants you to know about.
This is the metadata found on the Half-Dome USGS Topo map. The metadata lets you see how old the various datasets that the USGS used to create the Topo map are.
The metadata for the City of Santa Clarita’s General Plan map contains similar information about data sources, disclaimers, who created the map, and a link to the original file used to create the map.
This article was originally written on November 20, 2016 and has since been updated.
Fonte : National Geographic
