1. Systems for locating points on Earth 1. Latitude and Longitude

2. Roadmaps locate points on a grid by the letter and number of its box , e.g. B4 or E1. This works but is not very accurate. For example, the two points in E1 below share the same locator but are not in the same place.
A B C D E F 1 2 3 4 5 6

3. We use several grid systems to locate points – much more accurately – on the surface of the Earth
The two most common grid systems are
Latitude and Longitude
Universal Transverse Mercator (UTM)
The Public Land Survey grid is used in many U.S. states
There are many, many local grid systems used for an entire country or parts of a country
India Grid A India Grid B Zimbabwe Grid, etc.
This help module focuses on Latitude and Longitude

4. A roadmap grid consists of boxes defined by horizontal and vertical lines
The latitude/longitude grid uses horizontal east-west lines called parallels of latitude and
north-south lines that converge at the North and South Poles called meridians of longitude

5. 90° N. Latitude = North Pole
The Equator is the reference place for Latitude. All latitudes are measured in degrees, minutes, and seconds north or south of the Equator e.g. 47°37’22”N Latitude
90° N. Latitude = North Pole
There are many points 30° N of the Equator. All lie on this line – the 30th parallel of North latitude
So is this point
This point is 30° North of the Equator
30° S. Latitude
60° N. Latitude
60° S. Latitude
30° N. Latitude
30°
30°
Equator
90° S. Latitude South Pole
(Think of the Earth being cut by a horizontal egg slicer)

6. The reference for longitude is a single meridian passing through Greenwich, England called the PRIME MERIDIAN. Longitudes are measured east or west of the Prime Meridian, e.g. 73°48’55” W. Longitude
Prime Meridian
0° E or W Longitude
60°
East Longitude
West Longitude
90° E. Longitude
60° W. Longitude
75° W. Longitude
90° W. Longitude

7. Any point on Earth can be located by combining latitude and longitude as in these simple examples.
34°27’09”N 52°19’52” W
And very accurately, using degrees (°), minutes (’) and seconds (”). There are 60 seconds in one minute, 60 minutes in one degree
30° S Lat. , 75° W Long.
0° N or S Latitude
0° E or W Longitude
45° N. Lat., 15° E Long.

8. GLOBE FORMAT FOR LATITUDE AND LONGITUDE
The most common format for latitude and longitude was used in the previous slides: degrees, minutes, and seconds e.g. 23°44’19” S Lat., 136°55’33”E Long.
To avoid problems with using the base 60, the required GLOBE format uses degrees and decimal fractions of degrees – no minutes or seconds at all – for example, ° N Latitude.
This means the same as 67°45’00” N Latitude because .75 degrees = ¾ of a degree = 45’.
Your GPS receiver can report latitude and longitude in several formats. Be sure to set it on degrees and decimal degrees. In the setup screen of the GPS, this will appear as hddd.ddddd°