Before we dive into the reading of GPS coordinates, it is important that you have a good grasp of the GPS system and basic knowledge of the geographical lines of latitude and longitude. Once you understand that, reading coordinates is very easy, and you can practice with online tools.
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.
Originally a system used only by the military, the GPS system became available for use by citizens almost 30 years ago. It is maintained by the U.S. Department of Defense.
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.
The image shows the lines of latitude and longitude.
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.
You can view more information on lines of latitude and longitude by watching this YouTube video using the link below:
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 image highlights a location in South America
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.
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 west”
40.689263 -74.044505 (DD)
Just to recap, 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.
Verifying GPS Coordinates
Google Maps is a great Internet tool for verifying the coordinates of places of interest.
Finding the Coordinates for a specific location
1/ Open Google Maps at https://maps.google.com/ and find the location of your place of interest.
2/ Right-click the location and select “What’s here?” from the small menu that appears.
3/ A small box will appear at the bottom indicating the name of the location and the coordinates in Decimal Degree (DD) format.
Verifying the Coordinates of a specific location
Open Google Maps at https://maps.google.com/. There will be a search bar at the top-left corner of the page.
Enter the coordinates into the search bar then press the Enter key or the Search icon. The coordinates can be in any of the three formats. Please note that the coordinates must be entered correctly.
Google Maps will indicate the location of the entered coordinates with a red pin.
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.
For mathematicians willing to perform the raw calculations, you can learn how to convert from DMS to DD and vice versa.
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.
GPS-enabled devices
To take advantage of the pinpoint accuracy of the GPS system, you need a GPS-enabled device. These devices communicate directly with the GPS satellites using low-powered radio waves. By communicating with at least three GPS satellites, a device is able to determine one’s location on the Earth with accuracy.
This link (PDF) is a poster that illustrates how the GPS system works in pinpointing your location with accuracy. GPS-enabled devices include:
GPS navigational devices
Companies such as Garmin and Magellan manufacture dedicated GPS navigation devices. They come in various sizes and may resemble a smartphone or tablet. These devices have special built-in software that utilizes the GPS system to assist persons in finding the shortest route to a particular location, locating places of interests, and much more. They are commonly used in vehicles, hiking, and particular sports.
Above is an image of a GPS navigational device; the Magellan RoadMate 2255T-LMB. You can find more information on the devices by following the link below:
http://www.magellangps.com/Store/RoadMate/Magellan-RoadMate-2255T-LMB
Smartphones
Most smartphones, especially high-end phones, are GPS-enabled and can be used as a navigational device if you have the right apps installed.
Mobile computers
Some laptops and netbooks are GPS-enabled and provide navigational information while on the go.
Computer peripheral devices
Devices connecting to the computer via USB, Bluetooth or expansion slots allow the computer to utilize the GPS system.
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