What is Geodesy?

(Good question)
Quite simply 'Geodesy' is the study of the shape and size of the earth.

Now I bet you're thinking to yourself, "Hey, I've seen pictures of the earth from space, from the Apollo Moon Missions, from the Shuttle, and the earth looks round to me." 

So, what's to study?

Well, the earth is almost round, but not quite. And, because the earth's not quite round, we need to know just what shape it is, so we can make accurate maps.

Why do we need maps?

(Another good question)
There's an old saying that goes something like, "You can't tell where you're going unless you know where you've been". After all, if you don't know where you are, how can you figure out which way to go, much less find your way home?

Use a map you say?

(Good idea).
Maps are just like pictures. Have you ever heard the phrase, "A picture is worth a thousand words"? Well, a good map can help us to make sense of all kinds of information and these days, any thing we can do to help us sort out the mountains of information we're faced with is a good thing! Pictures, or maps, make these large amounts of information much easier to understand.

Maps play a big role in our life. For example - when you invite a friend over for the first time, you'll probably need to give them directions so they can find your house. You might tell them to follow a certain street, go past the convenience store and turn right at the playground to get to your house. In other words, you use 'landmarks' to describe to your friend where you live. Landmarks are places, buildings, roads etc. that are easy to identify. They give your friend a helping hand to find your house. If you make a picture of the landmarks and how to use them to find your house, well, you've made a map. A map is easy for you to draw, because you know the turns and landmarks near your house and it's easy for your friend to follow, because they can just follow the pictures!

Mankind has used local landmarks dating back thousands of years. "Travel towards the largest mountain peak 'til you come to the big rock, I live under the biggest tree you can see", might have been directions to find your friend's house if you lived back then.

Today, we often use convenience stores, schools or playgrounds as local landmarks. But what if your friend was from out of town ­ and didn't know how to get to any of the local landmarks, what then?

You say we need better maps? You say the maps need to cover a larger area, have more detail, more 'landmarks'? Sounds to me like you're getting the picture. (Pun intended).

In order to make larger, better maps, we need to use something called a spatial reference system. A spatial reference system defines the way that any location (trees, houses, roads, buildings etc.) can have its own unique address. Well, for us to have a good spatial reference system, we really need to need to know about the shape of the earth. One thing always leads to another.