HTML5 Geolocation

Chapter 2. Geolocation: Latitude, Longitude, and More

In Chapter 1, we covered the basics of geolocation, including what geolocation means, how geolocation information is gathered from different sources depending upon the device, and some common applications that implement geolocation today. Several key terms have also been mentioned, like latitude, longitude, and altitude; yet no definition has actually been given for any of these terms. Perhaps you are already well-versed in the GIS vernacular, but in case you are not, this chapter is meant to give a better understanding about exactly what information the W3C Geolocation API will be giving the developer. Recognizing exactly what information you are being passed and how to manipulate it properly will allow you to build better applications, if for no other reason than so that you will not misinform the end-user about the data.

What Are Coordinate Systems?

We have discussed the location (position) for a device, found using GPS or some other location method, given in latitude and longitude. These are called the coordinates of the particular device. In order to locate a device on the Earth, it is given a set of numbers which represents its place on the globe. These numbers make up the system by which we can then extrapolate positions.

There are many types of coordinate systems used in mathematics and everyday life—in fact, the most basic of coordinate systems was most likely taught to you when you were first learning to add and subtract: ...