GIS: What is Geographic Data? How Is It Mapped?

"Normal" data can be thought of as the building blocks of information. In modern times, it is often information that is compatible with computers and its inner workings.

Geographic data is simply a collection of information that can describe objects and things with relation to space. Often this is done with x,y coordinates or longitudes and latitudes.

So what does this mean for GIS users?
Well geographic data is at the heart of what makes for interesting maps. Without this data, there would be no information that would need to be visualized and analyzed.

ESRI has a great video with a clear example of how geographic data can be visualized. This presentation by Paul Trevillion and Eric Bowman clearly explains how geographic dtaa works and even where you can get it from. It is a bit lengthy but it is very clear in its explanations.
http://video.esri.com/watch/628/what-is-geographic-data-and-where-can-i-...

The example used actually talks about movie rentals by zipcode. This really interested me as the data I have been given is organized by zipcodes. The presentation gave me inspiration on how to cartographically treat the data once it is opened up.

Now data can be gotten from many different sources and in the GIS world, data is passed on like heirlooms from person to person. There are sites like the USDA and other government funded sites that maintain data. However, with most data comes the tendency for information about the data to be lost.
Now your probably wondering what's the point about having data about data! The first time I heard this, I thought it was ridiculous too. But when you start working with clunky data, you realize that data about data, also known as metadata, will save your life.

There are things about spatial data, or geographic data,that make it necessary for you to look up metadata so that all the data you work with line up with one another visually. The first basic concept that you would need to know is that the earth is a 3d object that is being visualized in 2d. With that comes distortions you are essentially flattening the globe to see it all. Now, there are different ways of flattening the globe. These different versions are called projections. You need all your data to be in the same projections so that boundaries of your spatial data match up with one another.

Metadata is crucial in determining the validity of your data. Metadata can also help you figure out what type of data you are working with. In geographic data there are two types of data files. You have vector files and raster files. Vector data uses solid lines and curves to visually depict spatial data while raster data uses pixels. Here is a good forum that describes the advantages and disadvantages of each type and when to use each.
http://gis.stackexchange.com/questions/7077/what-are-raster-and-vector-d...
Finally, it can also help you with things like finding out how old the data is, what its constraints are, etc.