SCSS Compass
and Orienteering

Contact Me

Direction- Grids

A “grid locator system” is a means of organizing and sectioning large areas of land so you can easily identify the exact location of something or someone. It’s like graphing.

Grids are an easy way to mark where things are on a flat piece of paper.

Most common grid systems:
- Latitude/Longitude (Lat/Long),
- Universal Transverse Mercator (UTM),
- Township/Range.

Grids like Lat/Long can be specified in degrees.

Geographic Coordinate System

Latitude

Lines of latitude are horizontal and parallel. Think of the word LAT and picture the bar on the A as a line of latitude. Lines of latitude run parallel to the equator and are called Parallel Lines or Parallels.

In the Lat/Long grid locator system the North/South coordinate (Latitude) is stated first then the East/West coordinate (Longitude).

Noteworthy lines of Latitude:

The equator is defined as 0° Latitude. Lines of latitude extend 90° North and South.

Tropic of Cancer = 23.5° North Latitude line.
Tropic of Capricorn = 23.5° South Latitude line.
The North Pole (True North) is 90° North Latitude.
The South Pole (True South) is 90° South Latitude.

Arkansas is approximately 35° North Latitude (we’re north of the equator)

You can find your latitude in the northern hemisphere by determining how high the north star (Polaris) is above the horizon.

Longitude

Greenwich, England is at 0° and is called the “Prime Meridian.”

Starting in Greenwich, England they extend around the Earth 180° East and West.

Lines of longitude run true north/true south and are called Meridian Lines or Meridians.

Because they run true north and true south, they are the most accurate way to determine true north on a topographic map.

Each topographic map gives you at least two lines of longitude; the left and right edge of the map.

Arkansas is at approximately 92° West Longitude (about ¼ of the way around the Earth west of Greenwich, England). Note: That’s why there’s 6 hours difference between central time and GMT (Greenwich Mean Time). 24 hours/4 = 6 hours.

Using lat/long, the coordinates of Benton, AR is 34.563° N, -92.587° W.

34.563° N is the Latitude, -92.587° W is the longitude.

UTM- Universal Transverse Mercator

This coordinate system is based on the metric system. The numbers in the coordinates are in meters. It is used for the Military, NATO, National Guard, and GPS. Despite its long name, it is actually very easy to use!

The UTM system has many other similar systems that are derived from it. A couple are:

USNG: US National Grid System

MGRS: Military Grid Reference System

To define a position of something you need a Zone (and section) along with Eastings and Northings inside that zone (more on this later).

UTM ZONES

UTM zones divide the Earth into 60 equal Longitudinal zones. Each zone is 6° (360 total).

The US spans from zone 10 to 19.
Zone 1 is west of Alaska in Russia. 180° west of Greenwich.
UTM does do NOT include the extreme North and South parts of the Earth.
Arkansas is in ZONE 15 and 16.

To get more detail of each Zone, each of the Zones is sectioned North to South into 8° bands or sections. These sections are labeled with letters from C (at the South) to X (at the North). Letters I and O are not used because it can be confused with the numbers one and zero. Benton, AR is in ZONE 15S.

Section N always starts just above the Equator designating North. Think of N = North. Letters before N are South of the Equator. Letters N and after are North of the Equator.

Once you find the right zone, you use “Easting” and “Northing” to find exact location of something inside that Zone.

Easting is like the X axis, and Northing is like the Y axis when graphing. Easting is always written first, followed by Northing. The Easting and Northing coordinates are in units of meters. Easting describes an east/west position, Northing describes a north/south position.

Eastings:

Easting is arbitrarily setup in each zone so that the 500,000 meter position is aligned with the Zone’s central meridian- it cuts right through the middle of the Zone. The number increases when going west to east. In the picture below, Hot Springs is in the middle of Zone 15S, so Hot Springs would have an Easting of 500,000 m.

The Easting “origin” for each zone would be 0 m at the most west part of each zone. BUT that would fall outside of the zone because the Zones aren’t that wide. Remember we are forcing 500,000 meters to be in the middle of the Zone. The zero origins are referred to as “false origins” because there are no places on Earth with a 0 Easting. Typical Eastings in a Zone are from around 300,000 meters to around 700,000 meters

Northings:

The Northing origin for the northern hemisphere is 0 m at the equator and increases to almost 10,000,000 m at the northern most part.
The Northing for each zone in the southern hemisphere is 0 meters at its southern most extent and increases to 10,000,000 meters at the equator.
Northing numbers always increase going NORTH. Northing numbers are usually much larger than Eastings. Northing numbers for the US are in the MILLIONS as opposed to Eastings which are normally less than 750,000.
Northings are specified in meters like Eastings.
In the picture above, Little Rock is near Northing 3,850,000 m.

A grid square is then formed on a map and is defined by horizontal and vertical grid lines.

UTM grids on maps have slight offsets due to the spherical nature of Earth. Think if you were to lay a piece of graph paper on a ball, it couldn’t lie flat. That’s the reason for the “offset” we’re talking about.

These offsets cause a slight deviation in the alignment of the grid with True North. The north direction on the grid is referred to as GRID NORTH and is usually less than 2° different from True North.

Grid North (GN): Usually very close to True North (<2°). It is the northward direction of a specific map based solely on the grid and is a result of depicting a 3D object on a 2D page.

The offset is usually indicated at the bottom of the map with the magnetic declination.
The grids on all US topo maps are 1,000 x 1,000 meters or 1 km x 1 km.

If you want to describe a grid square, it’s referred to by the Easting and Northing values of the intersection of the grid lines at the lower left corner of the grid square.

Now that you can locate a point using the UTM system, you can tell the distance between two UTM coordinates because the coordinates are in meters.

Bryant Marker 15S 545,987 (Easting), 3,830,823 (Northing) All in meters

Hurricane Lake Marker 15S 542,871, 3,830,807

Benton Marker 15S 537,542, 3,825,676

Benton Gun Club Marker 15S 548,560, 3,820,428

Shannon Hills Marker 15S 554,928, 3,830,589

Saline County Fairgrounds 15S 535,812, 3,824,458

Now you can find the distance between two locations as well.

Bryant marker is EAST of the Hurricane Lake marker. Because 542,871 m is less than 545,987 m and Eastings increase west to east.
The Bryant marker is just NORTH of the Hurricane Lake marker. Because 3,830,823 meters is greater than 3,830,807 meters.
The Bryant marker is 16 meters north of the Hurricane Lake marker. Because 3,830,823 meters - 3,830,807 meters = 16 meters
The Bryant marker is 3,116 meters (or 3.116 km) east of the Hurricane Lake marker. Because 545,987 meters - 542,871 meters = 3,116 meters.

UTM forms the basis for other modern grid systems that are very similar. The differences are minor and are only in the way the coordinates are displayed.

For instance, Saline County airport is at:

UTM 15S 547326, 3827476 Universal Transverse Mercator

USNG 15S WU 4732 2747 US National Grid System

MGRS 15SWU47322747 Military Grid Reference System

Notice, all UTM coordinates appear as:

Zone, then Grid Square*, then Easting, then Northing.

*Only for USNG and MGRS. Easting and Northing only 4 digits.

USNG used by FEMA, 911 dispatch, GPS, SAR, First Responders

Military use for MGRS extends to NATO, National Guard.

Township and Range

An older system used for surveying. Still often used for real estate purposes.
Dates back to the late 1700's. Still shown on USGS Topographic maps.
The Township and Range grid system is shown with red lines on US topographic maps.
- The grids are somewhat arranged North/South, East/West, but they are NOT representative of True North!

Large parcels of land are referenced to a Baseline and Principal Meridian. A grid is formed around the Baseline and Principle Meridian. See picture above.
- The “Baseline” runs across the middle of the parcel of land from East to West. Fun Fact: Baseline Road in Little Rock is the baseline for the grid in Arkansas.
- The Principal Meridian divides this parcel of land East and West. The Principal Meridian itself runs North to South.
- “Townships” are formed from the grid just described.
- Each "Township" is referenced by simple coordinates called Township and Range.
- Each Township is a group of land that is 6 miles x 6 miles.
  - Each Township is 36 square miles.
T and R Coordinates:
- A Township's position North or South of the baseline are specified by the Township coordinate.
- The Township's position East and West of the Principal Meridian is specified by Range coordinates.
- If the Township is 1 grid NORTH of the baseline, it is T1N. If a Township is 3 grids SOUTH of the baseline, it is T3S. If a Range is 3 grids WEST of the principle meridian it is R3W. Etc...
- So if you buy land that is in the grid formed 4 grids North of the baseline and 3 grids East of the Principal Meridian, the land is in T4N, R3E (Township 4 North, Range 3 East).

Each Township is further divided into 36, 1 mile x 1 mile grids called a “Section” to allow more detailed locations inside a Township.
Sections are labeled 1 to 36 starting in top right corner. In the first row, it increase right to left and at the left, goes to the next row and increases from left to right. Continues back and forth.
From there, more detail is given by descriptive wording added to the coordinates like "Eastern 1/2 acre".

Sections in a

Township:

Township and Range on a US Topographic Map:

SCSS Compass and Orienteering

Direction- Grids

SCSS Compass
and Orienteering