Several different coordinate systems are used by search and rescue groups. Sometimes it is necessary to interface with other agencies, such as, the Civil Air Patrol, that use coordinate references that are not standard to ground search and rescue teams. The common factor of all of the diverse maps and systems used by the many agencies that might become involved in a search is that they can be related to the 7 1/2 minute topo maps that search and rescue field teams carry.

The difficulty faced by all of the coordinate systems is the projection of features from the ellipsoidal Earth onto a two dimensional map that can conveniently be used for navigation purposes. Early in the history of long distant sea navigation, mariners began using the height of the star Polaris above the horizon at night and the characteristics of the Sun's path across the sky during the day to provide a rough indication of how far north or south they were. It was not until the chronometer was developed in 1735, that east-west traversal could be accurately tracked.

In 1884, geographers from throughout the world met in Washington, DC and established the current format that we use for the latitude and longitude coordinate system. The baseline for latitude measurement is the equator and the baseline for longitude measurements is half of a great circle passing through Greenwich, England. Geodetic latitude and longitude are measured as angles with the origin of the angular measurements at the center of the Earth. The latitude value indicates the angular measurement above or below the equator, with a latitude at the equator being zero degrees. Longitude lines are the intersection of the earth's surface and a plane going through the Earth's north-south (rotational) axis and the point of interest on the Earth's surface. Zero degrees longitude is the longitude line passing through Greenwich, England. The height measurement at a point is taken with reference to Mean Sea Level. Latitude and longitude values, listed as degrees-minutes-seconds, are adjacent to black tick marks on the border of USGS topo maps. For navigation purposes, angles and lengths are not preserved in the latitude and longitude coordinate system. Over short distances, the differences are so small that they are insignificant, but over long distances these differences become very important.

The UTM system is one of several grids that have been developed to simplify calculating directions, distances, and positions, primarily for ground military operations. During World War I, the French military found that they had significant problems in rapidly and accurately calculating pointing angles for their artillery when using the latitude and longitude system. The rectangular grid system that the French adopted for their artillery fire control is the origin of the UTM system. By the end of World War II, there were over 100 different grid systems in use around the world. To establish a consistent system, NATO standardized on the UTM system for its member nations and it is currently used by the US military for ground military operations. UTM is a rectangular system, with meters as the units for the coordinates.

In the UTM system, the earth is divided into 60 UTM zones, each zone segment composed of a region defined by the area between two longitudinal lines that are six degrees wide. The zones can be thought of as segments of an orange peel that has been cut into 60 equal segments, then, peeled and flattened back. Zone 1 begins at 180 degrees west longitude and extends to 174 degrees west longitude. Each zone is a rectangular grid, with points in the zone represented by Cartesian referenced to an origin at the intersection of the middle longitude line (called the central meridian) and the equator. Grid points are measured east and north in meters, basically, an x-y coordinate system. For the northern hemisphere, grid point values are measured continuously from zero at the equator and increasing the further north the grid point is located. The central meridian, the middle longitude line in the zone, is assigned an east value, called a false easting, of 500,000 meters. This assures that there are no negative coordinate values in a zone. East-west grid values to the west of the central meridian are less than 500,000 meters and to the east, more than 500,000 meters. To complicate matters, for grid coordinates in the southern hemisphere, the origin continues to be the intersection of the central meridian and the equator, but the origin is given the arbitrary value 500,000 meters east and 10,000,000 meters north. Grid points south of the equator have a longitudinal (y-axis) component of less than 10,000,000 meters. Blue tick marks on the topo map edge represent the UTM 1,000 meter grid with associated numbers indicating the grid coordinates in meters.

Some Search and Rescue teams use a very simple system that provides position coordinates as offsets in inches from the bottom left or right corner of the topo map border used. Care must be taken to use the border around the topo map and not the physical edge of the map, which may vary from map to map. The National Association for Search and Rescue (NASAR) refers to the system as the San Diego Mountain Rescue Team system. It requires that the team know their location on the map and that both the sender of the coordinates and the recipient are using the same map.

The Uniform Mapping System (UMS) is based on Sectional Aeronautical charts and, also, keyed to 15 minute series topo maps. The 15 minute topo maps can be quartered to defined a 7 1/2 minute quadrant. A UMS position on a topo map is given as horizontal and vertical offsets in miles from the lower right corner of the border of the topo map.

The range and township coordinate system was utilized as an early effort to map the area of the United States west of the Ohio River. The mapping survey was begun in 1784 with the intention of the survey preceding the settlement of new territories. In each area to be surveyed, a reference point was established, from astronomical observations, upon which the survey would be based. From the reference point, a true north-south line was projected to the limits of the area to be surveyed. Also from the reference point, an east-west line, following a true parallel of latitude, was projected to the limits of the area. Parallel to the reference lines, townships, as nearly six mile square as possible, were formed. Townships were further divided into one mile square sections. A column of townships extending north-south is called a range and a row of townships running east-west is called a tier. (Over time, the term township replaced tier in the range-township terminology.) Sections can be quartered repeatedly to define a position. The township and range designations are listed in red numbers and letters at the edges of topo map borders. Regions covered by original Spanish land grants were excluded from the range and township survey.