## GPS

### Emma Wright, Kadijah Francis, heather yi

What is a GPS?

GPS devices (or Global Positioning Systems) are defined as a system of satellites which can pinpoint a user's location on the Earth to within a few meters.  GPS receivers are parts of the GPS system, which calculate the GPS's distance from satellites in space.  We use GPS in our everyday lives:  on our phones, in our cars, and just to help us pinpoint our location in general.

2d vs 3d GPS

The image above is an example of 2d GPS.  This is a 2 dimensional GPS system, where only 2 satellites are needed, plus the Earth itself.  In the image above, you can see that the two satellites, and the Earth are interacting at the same point, showing the exact location of the GPS.  3d, or three dimensional GPS is the same concept, except instead of circles intersecting, spheres intersect, instead.  To get a 3d position on the Earth's surface, three satellites are needed, plus the Earth, though since there are 29 satellites circling the Earth, many GPS receivers use more than 3 satellites to improve accuracy.

Triangulation, or how GPS works

Triangulation is the process of determining where a GPS receiver is on the Earth, using 2d or 3d positioning, and several GPS satellites.  The first step in triangulation is imagining a "distance sphere" surrounding a GPS satellite:  point on the surface of the sphere are all the same distance from the satellite that's located exactly at the center.  Second, the distance from one satellite places you somewhere on a spherical surface centered around the satellite.  Next, figuring out the distance from two satellites places you somewhere along a circle that's between the two satellites.  Then, the third satellite is brought in.  The distances from three satellites usually intersect at two points, and one of these point should be on the Earth's surface.  In simpler terms, this process works by finding the intersection of your distances from three or more satellites.  Below, a video helps to better explain the process of triangulation.

Source:

http://www.how-gps-works.com/faq/q0110.shtml

Pros of using a GPS system

There are several pros of using a GPS system.  One is location.  GPS units provide you with a simple, easy route to get to your location.  Establishing coordinates or position with a GPS is much easier than with a map.  Another pro is navigation.  GPS devices make navigation much easier, and provide a distance to a preset location almost instantly.  When using GPS-based maps, one can also see and navigate according to terrain features.  Functions is another pro of using GPS.  In addition to navigation, many GPS receivers include functions like barometric altimeters, an electronic compass, and time and date.  The last pro is that GPS include other features, such as a variety of map data and routes, so that a user has instant access to a lot of information.

Source:

http://www.trails.com/facts_5327_pros-cons-gps-systems.html

Cons of using a GPS system

However, there are also several cons of using a GPS system.  One con is that there can be system issues.  Since GPS devices rely on satellites, they aren't perfectly suited to outdoor use.  Interference from dense foliage, caves, and even canyons can cut off communication when a user most needs it.  Another con is that of reliability.  Like any electronic device, GPS systems are subject to failure from dead batteries, or other malfunctions.  While you can limit the chances of this happening, it is still a potential concern.

Source:

http://www.trails.com/facts_5327_pros-cons-gps-systems.html

Overall, the pros of using GPS systems outweigh the cons, and we believe that GPS systems should be used often, as they are a great benefit to travel and to life in general.