Maps

*The following information relies heavily on personal experience and the National Association for Search and Rescue's (NASAR) Fundamentals of Search and Rescue 2nd Edition handbook.*

Learning Objectives.

After reviewing all of the contents of this page, you must be able to:

  • Describe what is meant by "georeferencing."

  • List three types of geographic coordinate systems.

  • Define contour lines, true north, magnetic north, grid north.

Georeferencing

Most of us are already using georeferencing without even realizing it. It can be as simple as telling someone to meet you at the corner of Sheldon Ave and Garnet St. or describing the bald eagle you saw perched on the tall white pine in front at the Gratiot Lake boat launch. By doing this, you describe a specific location on the globe that someone can use to help identify what you are talking about. Search and Rescue operations can take place over a wide area, and it is important that everyone who is involved in SAR efforts understand how to communicate their location in a way that can be translated to a map.

Geographic Coordinate Systems

Coordinates are an effective way of referencing a point on the Earth. The most common use is imaginary vertical lines running from the north pole to the south pole, and imaginary horizontal lines running east to west. The vertical lines are known as meridians and are referred to as lines of longitude. The horizontal lines are known as parallels and are referred to as lines of latitude. Watch the video below to better understand how longitude and latitude can be used to locate a position on the Earth:

Universal Transverse Mercator

Using latitude and longitude are great for traveling long distances, especially by air or sea, but for more efficient travel overland, the United States military created the Universal Transverse Mercator (UTM) projection. Understanding the concept of map projections is not essential for a basic map reading course, but if you are curious about it, you can learn more here. As for the UTM projection, essentially, if you took a flat map of the earth, and covered it with little squares that represented one meter by one meter on the ground, you would have a UTM map. Watch the video below to better understand how the UTM is utilized in map reading:

United States National Grid

The United States National Grid (USNG) is the primary georeferencing source used by state, fire/rescue, and Federal Emergency Management Agency (FEMA) Urban Search and Rescue teams. NASAR also recommends that land SAR technicians utilize the USNG as the primary method of georeferencing. This system is functionally equivalent to the Military Grid Reference System (MGRS), and its coordinate values are identical to UTM values. The video below explains the use of a USNG map, and you will notice the similarities between how to use this type of map mirrors how you would use a UTM map:

U.S. Public Land Survey System

When land across North America was first being measured and mapped, professional surveyors brought a bag that held a chain that was exactly 66 feet in length. They would stake the end of their chain, and pull out the chain to its full length, taking note of any important land features they found along the way. A chain is a unit of measurement, 66 feet in length that are still being used today. Although accuracy has improved over time, this was the start of the U.S. Public Land Survey System (USPLS). Eventually, these measurements were divided into parcels of land called townships, which are 6-miles by 6-miles. Townships were further broken down into 1-mile by 1-mile parcels (640 acres) called sections. If a USPLS system is encountered on a map, it is important for SAR personnel to realize that many of these lines do not follow the more modern USNG or UTM accuracy (some have not been changed since they were first transcribed circa1785). It is an important system to understand in the United States since most property is described with a USPLS coordinate, and you may be told where a person was last seen based on a Township/Range description. Watch the video below to learn more about this system and how it was used:

Topographic Maps

A map is a graphical representation of the Earth's surface as seen from above, and it is important for land SAR operations to utilize maps that offer the most functionality. Topographical (topo) maps, not only represent the Earth's surface, but also portray elevation with the use of contour lines, shades of color to portray water, vegetation, or man-made objects, and have a robust map key to help identify everything on the map. Contour lines connect all the points at the same elevation above sea level. The distance between contour lines should be described somewhere in the bottom margin of the map, usually near the distance scale. Contour lines that are close together indicate steep terrain, whereas lines that are far apart indicate flat or gently sloping terrain.

Topographical maps should also have a declination diagram that indicates the relationship between the true north and the magnetic north. True north is a fixed point on a globe, and magnetic north is where the magnetic field of the earth draws the needle of a compass. It is important to note that the magnetic north is constantly changing, sometimes slowly, other times more dramatically. If you find yourself with an older map, it will be a good idea to check if the declination diagram is still accurate. A declination diagram may also show the relationship between grid north and true north. Grid north is the north-south direction of the lines on a UTM, MGRS, or USNG map, and will deviate from true north and magnetic north depending on your location in the United States.

Watch the video below to get a better understanding of how to read a topographic map:

Useful Tools

​These links will bring you to tools that will help you convert coordinate systems. For example, if you wanted to convert a latitude/longitude system to a UTM coordinate:

The USGS has many topographical maps available online.

This website provided by the FCC will let you know if you will be in the range of cellular coverage.

Looking for a useful map, you can find many at the National Map Services website.

Or install the Public Land Survey System tool into Google Earth.