If you enjoy hiking or backpacking, you have probably been using a topographic map. It is important to know how to read latitude and longitude on a topographic map to get the most use.
In this blog post, we will explore how coordinates work on a topographic map and how they are used for navigation. We will also discuss how longitude lines can be used with latitude degrees to identify features on the map, such as mountains and valleys.
How Do You Find Coordinates on a Topographic Map?
On a topographic map, coordinates are represented by small numbers located in the corners of each map sheet. To find coordinates on a topographic map, you will need to know how to read both latitude and longitude lines.
You can measure latitude from the equator and is indicated by degrees north or south of the equator. Measure longitude east or west of the prime meridian and is also indicated by degrees.
Together, latitude and longitude lines create a grid that covers the Earth’s entire surface. You can use these coordinates to pinpoint any location on the topographic map.
Using a topographic map, you can pinpoint your location anywhere in the world by reading coordinates located in each corner of every topographic map sheet.
The most important thing to remember about longitude is that it runs from east to west and does not run through Greenwich, England which would make it negative. Latitude lines vary because they follow latitude degrees north or south of the equator.
How to Read Latitude and Longitude on a Topographic Map
The first step to reading latitude and longitude is to find the true north on your map. A star on most topo maps represents the true north. Once you have located true north, you can find your location’s latitude and longitude coordinates.
Latitude is measured in degrees from the equator, so locate the 0 degree line on your map. This will be at the equator. Then measure how many degrees your location is north or south of the 0 degree line.
For example, if you are located at 45 degrees north latitude, you are 45 degrees north of the equator.
Longitude is measured in degrees east or west of the prime meridian. Locate the prime meridian on your map. This will be at 0 degrees longitude. Then measure how many degrees your location is east or west of the prime meridian.
For example, if you are located at 120 degrees west longitude, you are 120 degrees west of the prime meridian.
Once you have found your coordinates, it’s important to note which direction they run. Latitude and longitude can be read horizontally or vertically on a topographic map.
How to Read Topographic Map Contour Lines
A topographic map is filled with lines that help identify elevation changes on the map. These lines are called contour lines, and they connect points of equal elevation on a map.
The closer together the two contour lines are, the steeper the elevation change between those two points. Contour intervals vary depending on the map’s scale.
Contour lines can help identify features on a topo map, such as mountain peaks, valleys, and ridges. By following a few key contours, you can get an idea of the shape and size of a geographical feature.
- Tall peaks will have more contour lines than short hills.
- Ridges and mountain passes have a topographic saddle, or a dip in elevation, at each end of their topo map segment.
- Valleys between mountains or ridges will display two sets of alternating longer and shorter contours, with the highest point being right above the lowest point on that set of contours.
To identify a topographic maps’ features, look for topographic saddles to locate valleys and pass-throughs or saddles. Look for diagonal patterns in alternating long vertical bar shapes to find ridge crests. Also, look for curvy “S” shaped horizontal line segments to show steep slopes around points such as sharp curves along roads or riverbanks.
Identifying Features with Contour Lines
A topographic map is a two-dimensional representation of the surface of the Earth. The data representing elevation, magnetic direction, and magnetic declination are collected by satellites orbiting our planet. Identifying features on a topo map with contour lines is essential for accurate navigation.
There are three coordinate systems on a topographic map: latitude and longitude, the Universal Transverse Mercator (UTM) grid, and the Military Grid Reference System (MGRS).
Latitude is measured in degrees north or south of the equator, while longitude is measured east or west of the prime meridian. The UTM grid divides the Earth into sixty zones, each six degrees wide. MGRS uses a ten-character alphanumeric code to identify locations anywhere on Earth.
The map grid overlay helps you determine your location on a topo map using either latitude and longitude coordinates or UTM coordinates. The grid’s origin is at the intersection of the equator and prime meridian and is represented by the letter “O” on a topographic map. The prime meridian is represented by a long, thin black line that runs east to west.
Magnetic north is your compass’s direction when you’re not magnetic interference. You can measure magnetic declination by checking the angle between magnetic north and true north. It’s essential to know magnetic declination when using a compass because it can cause your bearings to be inaccurate.
A contour line connects points of equal elevation above or below sea level on a flat surface like a map. A contour interval is a vertical distance between two adjacent contour lines on a map, and it’s usually given in meters or feet. Elevation data collected by satellites is used to create these contour lines on a topographic map
When using a compass to take bearings, you should not use magnetic north instead of true north. This is because magnetic north can change over time and location due to magnetic interference.
To compensate for this, you need to know your magnetic declination. You can find your magnetic declination online or in a local hunting or fishing store.
How Do You Read Elevation on a Topographic Map?
The elevation is given in meters or feet above sea level. The closer the contour lines are, the steeper the slope of the terrain is. So, contour lines on your topographic map, which are far apart, indicate a flat surface. The hatched area between two contour lines is called an interval band, and it’s usually colored brown or black on a topographic map.
Reading and Interpreting Contour Lines on a Topographical Map
To find out the coordinates of a point on a topographic map, locate two intersecting west lines, represented by solid black lines, and then measure horizontally from one line to the other.
The number located at this intersection is your coordinate reading for that point. Remember that east lines run vertically on a topographic map, so north-south measurements are always west to east.
To determine an elevation, locate a contour line that passes through your point and then follow it in the direction indicated by its orientation (up or down). The number located at this intersection is your height reading for that point. Always read west to east on topographic maps.
Lastly, here is a short list of key features of a map that will help you understand how to find different locations on your map:
- West lines: Solid black lines on a topographical map that indicate the intersection of east and west coordinates
- Dotted lines: Light blue dashed lines on a topographical map that represent elevation changes
- Blue ticks: Small tick marks along the map grid that indicate elevation reading
- Contour lines: Dark green squiggly lines on a topographical map that show changes in elevation. The spacing of the contours indicates how steep or gradual the slope is, while the direction of the contours shows whether a feature slopes up or down
- Declination: West lines (solid black) are always at a lower elevation than east lines (dashed blue). This phenomenon is called declination, and it affects how you read coordinates on topographical maps
- Map grid: Parallel horizontal and vertical lines that run throughout a topographic map. They help with finding longitude/latitude readings and height measurements
- Tick marks: Small tick marks along the map grid that indicate elevations. They can be either blue for west ticks or green for east ticks
Conclusion:
If you’re out living in the wilderness, hiking or hunting, it’s important to know how to use a compass and how to read elevation on a topographical map. Understanding how to read latitude and longitude on a topographic map can help you plan your route, avoid dangerous areas, and find your way back home.
The more familiar with how maps work, how to measure height, and where latitude and longitude readings are located, the better prepared you’ll be for getting lost or exploring new territory.
