In GIS and Cartography, our overall goal is to map representations of reality, analyze spatial problems, and deliver the content in a meaningful and useful way. If the world was flat, the job of the cartographer would be one of simple scale: create documents where 1 map unit equals 125,000,000 real world units, print ‘em out, fold ‘em up, and sell them. Easy as pie. But the Earth is, regardless of some strongly held views, a sphere-like shape and requires some creative thinking on how to get the round Earth to be a flat map.
In order to create the maps (a graphical representation of the physical world) we need, the very first step is to create a system which labels all the locations on the Earth’s surface. Think of it this way - if I asked you to draw a map of your neighborhood, you would most likely draw the streets, some houses, some trees, and maybe your favorite college or coffee shop. And then if I asked you to label the map you just drew, how would you go about it? You might use street names and building numbers, or you might use landmarks such as "the big pink house" or "the giant maple tree on the corner". Regardless of how you label the map, you are giving it context - a means of identifying your neighborhood as a specific place and not just some random neighborhood you drew. If you then gave that map to a friend who was coming over to visit for the first time, ideally they could use it to come over for that very important sporting game.
When it comes to the need creating accurate maps of both large and small area, we need to figure out how we are going to label the features we draw. The first thing we need to do is establish some sort of world-wide system to create labels for all locations, both those in the city where labels are pretty easy to create, and those locations where nothing exists, what we could (fictitiously) call an "Earth Address System". Similar to a grid of streets in a neighborhood creating a means of navigation and logical labels, we create a grid which covers the Earth's surface and label the lines and the intersections of those lines. This grid and it's labels must be logical, simple to understand, and stand the test of time. Just like "JFK Drive" wasn't "JFK Drive" in 1935, we can't just use currently relevant labels for our world-wide system. The system must be independent of any culture, language, or time period. It must also be based on the entire planet, using the Earth as the means for creating the system (which we will later learn is called an Earth-fixed, Earth-centered system). Only when we use an system independent of creators can we have a system which can mathematically (the universal language) express a label for every single point on the Earth's surface. And once we know how to label the round Earth, we can tackle to problem of creating flat maps.
This is our goal of this chapter: we will look at the steps it takes to go from the round Earth as we experience it (the topographic surface) to a geographic coordinate systems (one kind of Earth Address System) in order to find and label locations on the Earth’s surface utilizing an angular unit of measure, such as degrees. We will explore latitude and longitude, one example of a geographic coordinate system. Once we’ve accomplished that, we can choose to take it a step further and create a projection or a planar coordinate system in order to work with a flat map and measure in linear units, such as feet, meters, and international feet.