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GPS Coordinates

GPS Systems Online

How to read GPS coordinates

If you have recently invested in a GPS system, you'll know that deciphering GPS coordinates can be a nightmare. Instructions in unit manuals are often complex and difficult to understand, making even the most simple of tasks sound like an elaborate and technical exercise.


Simply put, coordinates refer to the position on a map where lines of longitude and latitude cross. Imagine the earth as being covered in a giant grid and each building, park and tree being a point where grid lines intercept. GPS receivers use satellite transmissions to determine the coordinates of specific locations. Mapping software then converts this information into a position on a map. Once a position has been established, the GPS unit can calculate important information such as the distance between two points or how long it should take to get to a specific destination.

GPS units can be used in two ways, to direct you from one place to another such as when you are driving to an unknown destination and to determine specific points of interest from coordinates. Systems designed specifically for driving will normally come with a large database of built-in maps. If you have a detailed map of the area in which you are traveling, and the address of the destination you wish to travel to, you need only enter your starting address and the address of your destination. The GPS unit will locate the points on the map and determine the exact coordinates of both locations. It will then be able to supply you with detailed information on how to get to your destination.

This approach can also be used on hiking trips where a detailed map containing waypoints has already been purchased or downloaded. Simply enter the names of the points of interest where you would like to hike and the GPS unit will calculate coordinates, directions and the best way to get from one point to another.

Finding the coordinates of an unknown destination is also really simple when you know how. Simply buy a GPS compatible map of the area you live in or the area you would like to visit. A map with a scale of 1:25,000 or 1:50,000 is the best bet. Calculate a route that you would like to travel on the map, marking off areas of interest and key points along the route. Make sure that you also mark off all the points where you might change direction or have a choice of direction. Find the grid references of each key point and number them in the order you plan to pass through them. These are the coordinates that your GPS unit will use to navigate.

Set your GPS receiver to a grid function and input the coordinates of the route you have selected as Waypoints into your GPS system. Then simply begin your route and use your Waypoints to navigate without the use of map or compass. This route can be stored in your Personal Navigator Files for future use.

Using coordinates to determine addresses or points of interest applies if you do not have a map of the area you are traveling in or wish to add personal landmarks to an existing map. Say for example that you were on a hike in a remote location and were using your GPS monitor purely to track your route. While you were hiking, you stumbled across a beautiful waterfall and wanted to record its location so you could revisit it on a future date. You would mark the waterfall as a waypoint on your GPS system, where it would be stored as a set of coordinates. The next time you were in the area you could simply enter the name of the waterfall and your GPS system would lead you straight to it.

Certain GPS units have numerical screens as opposed to mapping screens. Planning a trip or hike using these types of units usually requires the use of coordinates. Using a handheld map, you would plot your hike from start to finish and determine the coordinates of all the areas you wished to hike through. You would then enter the coordinates as waypoints on your GPS receiver. Before you set out on your hike you would enter the coordinates of your starting position as a waypoint. The GPS receiver would then direct you to all the areas you had previously entered. Most handheld GPS units are able to store in the region of 200 waypoints, with some more sophisticated models being able to store between 400 and 1000 waypoints. The only disadvantage to units that do not have mapping screens is that it is harder to determine your position in relation to relative waypoints.

Until a GPS receiver has locked on to three or more satellites, any coordinates it provides will be virtually useless. Depending on the model of GPS unit that you are using, initial lock on time is likely to be in the region of five minutes. Subsequent signal establishment time will be significantly shorter, around 60 seconds in most cases. Another fact to keep in mind is that while GPS monitors may lead you on the straightest path between two waypoints or sets of coordinates, they will not take into account obstacles such as trees and ravines. It is therefore advisable to keep your eyes firmly focused on the path ahead whilst walking rather than to watch your progress on the screen of your GPS monitor.