Subscribe to Diving Deeper

Ocean Service Feeds

What is a Podcast?

A podcast is a an audio file published on the web. The files are usually downloaded onto computers or portable listening devices such as iPods or other players.

Read more about podcasting from

Find other podcasts from the US government

Diving Deeper Shorts: Episode 7 (January 13, 2011) - Geodesy

HOST: Today on Diving Deeper Shorts, we revisit our previous interview on geodesy with Dru Smith from NOAA’s National Geodetic Survey.  

Let’s listen in.

HOST: Dru, I have to tell you that geodesy wasn’t a word I was very familiar with before preparing for this interview. Will you tell us what inspired you to study geodesy in the first place?

DRU SMITH:  Sure, Kate. I was actually studying Land Surveying in college and during my senior year, I took a course called Elements of Geodesy. That was also the first time I’d heard that word. That course basically took the flat Earth world of surveying that I’d been studying and put it on a curved Earth. It opened my eyes to a whole new way of measuring the world. I absolutely loved the course and I decided to stay on and study geodesy through my Ph.D. After I finished, I joined the National Geodetic Survey and I’ve been here ever since.

HOST: Dru, how do we measure points on the Earth’s surface?

DRU SMITH: Well, geodesists, that’s what scientists are called who study geodesy, basically assign coordinates, which is kind of like a unique address, to points all over the Earth. If you were to stick pins in a model of the Earth and then give each of those pins a coordinate, you’d be doing what geodesists do. Before the space age, geodesists used to determine the coordinates of points by using Earth-based surveying tools, measuring angles, distances between points. Now most of our work is done using space-based tools like the Global Positioning System or more commonly known as GPS. But no matter what the tool is, geodesists still do the same work, which is very accurately defining the coordinates of points on the surface of the Earth in a consistent manner. This set of accurately measured points then becomes what we call a spatial reference system, which is basically a system that allows different kinds of maps to be consistent with one another.

HOST: Dru, what are some of the other benefits of geodesy?

DRU SMITH: That’s a good question Kate. Some of the other benefits of geodesy are, for example, to the transportation industry. So here’s a great example, I really love this one. By providing charts that are accurate to centimeters and using GPS technology on a ship which also can position the ship to centimeters, if those two locations are done consistently, say in the National Spatial Reference System., then you have the ability to know where the bottom of that ship is relative to the bottom of the ocean to a couple of centimeters and this means that a ship could put on extra cargo, sink deeper into the water, and still know that they’re safely navigating through a channel. And the beauty of that is more cargo directly relates to an economic benefit to the shipping industries. So, extra accuracy due to geodetic tools allows the shipping industry to have a pretty significant economic benefit.

That’s all for today’s Diving Deeper Shorts, where we highlight a few minutes of your favorite Diving Deeper episodes.

Want to learn more? Go to and select the May 2009 podcast archive to listen to the full interview with Dru Smith on geodesy.

You can catch the next episode of Diving Deeper on January 27.