In this video you will learn how to use the map to give a grid reference of your location.

#### Introduction to GPS

GPS stands for Global Positioning System; a system used for worldwide navigation and surveying. It is commonly used for pinpointing one’s exact location anywhere on the Earth’s surface and obtaining the current time at a specific location.

This is made possible by the network of 24 man-made satellites, called GPS satellites, which orbit above the Earth at great speeds and precision. Using low-powered radio waves, devices can communicate with the satellites to accurately determine one’s location on the globe.

**Latitude and Longitude**

The GPS system makes use of the geographical lines of latitude and longitude to provide coordinates for a person’s location or a place of interest. Reading and understanding GPS coordinates requires a basic understanding of navigation using the lines of latitude and longitude. Using both sets of lines provides a coordinate for the different places around the world.

**Lines of Latitude**

Lines of latitude are horizontal lines that stretch from east to west across the globe. The longest and main line of latitude is called the Equator. The Equator is represented as 0° latitude.

Moving north of the Equator, each line of latitude increases by 1°. Therefore, there will be lines of latitude representing 1°, 2°, 3°, and so on up to 90°. The image above only displays the 15°, 30°, 45°, 60°, 75° and 90° lines of latitude above the Equator. You will notice that the 90° line of latitude is represented by a dot at the North Pole.

All lines of latitude above the Equator are indicated with the letter ‘N’ to denote north of the Equator. Therefore, we have 15°N, 30°N, 45°N, and so on.

Moving south of the Equator, each line of latitude increases by 1° as well. There will be lines of latitude representing 1°, 2°, 3°, and so on up to 90°. The image above only displays the 15°, 30° and 45° lines of latitude below the Equator. The 90° line of latitude is represented by a dot at the South Pole.

All lines of latitude below the Equator is indicated with the letter ‘S’ to denote south of the Equator. Therefore, we have 15°S, 30°S, 45°S, and so on.

**Lines of Longitude**

Lines of longitude are vertical lines that stretch from the North Pole to the South Pole. The main line of longitude is called the Prime Meridian. The Prime Meridian is represented as 0° longitude.

Moving east of the Prime Meridian, each line of latitude increases by 1°. Therefore, there will be lines of longitude representing 1°, 2°, 3°, and so on up to 180°. The image above only displays the 20°, 40°, 60°, 80° and 90° lines of longitude east of the Prime Meridian.

All lines of longitude east of the Prime Meridian are indicated with the letter ‘E’ to denote east of the Prime Meridian. Therefore, we have 15°E, 30°E, 45°E, and so on.

Moving west of the Prime Meridian, each line of latitude increases by 1° as well. There will be lines of longitude representing 1°, 2°, 3°, and so on up to 180°. The image above only displays the 20°, 40° 60°, 80° and 90° lines of longitude west of the Prime Meridian.

All lines of longitude west of the Prime Meridian are indicated with the letter ‘W’ to denote west of the Prime Meridian. Therefore, we have 15°W, 30°W, 45°W, and so on.

Video about Longitude and Latitude

**Reading Geographical Coordinates**

Global navigation makes use of lines of latitude and longitude to pinpoint a particular location on the Earth’s surface. It is given as geographical coordinates.

The location is found along the line of latitude 10°N and along the line of longitude 70°W. When outlining the coordinates of a location, the line of latitude is always given first followed by the line of longitude. Therefore, the coordinates of this location will be: 10°N latitude, 70°W longitude.

The coordinates can be simply written as 10°N, 70°W

However, most locations on the Earth do not fall along the lines of latitude or longitude, but within the shapes created from the intersection of the horizontal and vertical lines. In order to accurately pinpoint a human being on the Earth’s surface, the lines of latitude and longitude are further divided and expressed in one of the three common formats:

1/ Degrees, minutes, and seconds (DMS) The space between each line of latitude or longitude representing 1° is divided into 60 minutes, and each minute is divided into 60 seconds. An example of this format is: 41°24’12.2″N 2°10’26.5″E

The line of latitude is read as 41 degrees (41°), 24 minutes (24′), 12.2 seconds (12.2”) north. The line of longitude is read as 2 degrees (2°), 10 minutes (10′), 26.5 seconds (12.2”) east.

2/ Degrees and decimal minutes (DMM) The space between each line of latitude or longitude representing 1° is divided into 60 minutes, and each minute is further divided and expressed as decimals. An example of this format is: 41 24.2028, 2 10.4418

The line of latitude is read as 41 degrees (41), 24.2028 minutes (24.2028) north. The coordinate for the line of latitude represents north of the Equator because it is positive. If the number is negative, it represents south of the Equator.

The line of longitude is read as 2 degrees (2), 10.4418 minutes (10.4418) east. The coordinate for the line of longitude represents east of the Prime Meridian because it is positive. If the number is negative, it represents west of the Prime Meridian.

3/ Decimal degrees (DD) The space between each line of latitude or longitude representing 1° is divided and expressed as decimals. An example of this format is: 41.40338, 2.17403

The line of latitude is read as 41.40338 degrees north. The coordinate for the line of latitude represents north of the Equator because it is positive. If the number is negative, it represents south of the Equator.

The line of longitude is read as 2.17403 degrees east. The coordinate for the line of longitude represents east of the Prime Meridian because it is positive. If the number is negative, it represents west of the Prime Meridian.

Verify that the following point of interest are as follows:

- What is at -28.778917, 114.614599 Anglican Church
- What is at -28.777297, 114.611768 St Francis Xavier Cathedral
- What is at -28.776717, 114.614422 Anglicare Geraldton WA 6530

**Reading Coordinates on Google Maps**

Most GPS devices provide coordinates in the Degrees, Minutes and Seconds (DMS) format, or most commonly the Decimal Degrees (DD) format. The popular Google Maps provides their coordinates in both DMS and DD formats.

The image above shows the location of the Statue of Liberty on Google Maps. The coordinates given for its location are:

40° 41′ 21.4” N 74° 02′ 40.2” W (DMS)

This is read as: “40 degrees, 41 minutes, 21.4 seconds north and 74 degrees, 2 minutes, 40.2 seconds east”

40.689263 -74.044505 (DD)

The Decimal Degree (DD) coordinates does not have the letters N or S to signify whether the latitude coordinate is above or below the Equator. Neither does it have the letters W nor E to signify whether the longitude coordinate is to the west or east of the Prime Meridian.

This is done through the use of positive and negative numbers. Since the latitude coordinate is positive, the coordinate is above the Equator. Since the longitude coordinate is negative, the coordinate is west of the Prime Meridian.

**Finding GPS Coordinates**

Google Maps is a great Internet tool for finding the coordinates of places of interest.

Finding the Coordinates for a specific location

- Open Google Maps at https://maps.google.com/ and find the location of your place of interest.
- Right-click the location and select “What’s here?” from the small menu that appears.
- A small box will appear at the bottom indicating the name of the location and the coordinates in Decimal Degree (DD) format.
- Click on the coordinates and in blue box top left coordinates are displayed in DMS format.

Converting between DMS and DD formats

There are various tools available on the Internet that can assist you in converting between the Degree, Minute and Seconds (DMS) and the Decimal Degree (DD) formats.

There are websites available that provide quick conversion between DMS and DD. Here is a link to a website that provides both DMS and DD coordinates for any specific location using Google Maps.

Google Maps:

http://www.mapcoordinates.net/en show Long Lat of points of interest.

http://www.bdcc.co.uk/Gmaps/ll_grat_v3_demo.htm show long Lat lines in DMS format

https://www.gps-coordinates.net/ Show location in all three formats.