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Making Waves: Episode 108 (Dec. 20, 2012)

This is Making Waves from NOAA's National Ocean Service.

We've got an oldie but a goodie lined up for the final podcast of 2012. Did you know that the National Ocean Service helps to ensure that Santa doesn't get lost on his journey around the country on December 25th. Here's an episode that originally aired way back in 2008 about Santa and the National Geodetic Survey. Enjoy!

We'll return with to our regular schedule of podcasts in January. Happy holidays.

(Santa and the NGS)

Many of us today own hand-held GPS device or have cars that tell us where to go by using advanced positioning technology. While knowing our exact position on earth is handy for us casual users, its essential for safe and efficient transportation in the air, on the land, or on the sea; and it's critical for laying out infrastructure like utility, energy, or communication systems. It's also essential to help Santa get around.

For 200 years, NOAA's National Geodetic Survey, part of the Ocean Service, has been in the business of delivering exact position information. To do this, the NGS maintains what is known as the National Spatial Reference System.

This reference system is used for mapping, navigation, and charting. Think of it as a highly accurate web of coordinate points on land and in space. These reference stations provide extremely accurate latitude, longitude, height, scale, gravity, and orientation throughout the u.s. At anywhere, anytime. It's what mapmakers use to make maps.

It takes a bit of explaining to get at how this complicated system works. For the past 200 years the NGS and its partners placed about 850,000 permanent survey marks throughout the u.s. These survey marks were the main component of the spatial reference system until a few decades ago. Today, the reference system is undergoing a major upgrade.

The revolution started in the 1980s, with the advent of GPS technology. This made it possible to locate points with greater accuracy and speed and at lower cost than ever possible before.

Most people think that GPS eliminated the need to measure position on the ground. But it's not as simple as that.

The global positioning system is made up of a constellation of satellites that orbit about 11,000 miles above the earth and broadcast radio wave signals. By determining the time that it takes for a radio wave signal to travel from a GPS satellite to a GPS receiver on the earth, the distance between the satellite and receiver can be calculated. That provides the receiver's location on earth. It sounds easy, but it's a very complicated process. It's also not perfect.

As advanced as GPS technology is, most commercially available GPS receivers are only accurate to within several yards. Considering that the earth is almost 25,000 miles in circumference, the difference of a few yards may not seem important. But there are many scientific, military, engineering, and toy-delivery activities that require much higher levels of positioning accuracy—often to within a few inches or less.

To provide measurements at this level of accuracy NGS came up with the idea of joining ground-based reference stations with GPS technology to develop what is called the Continuously Operating Reference station network, or CORS for short.

Each station in the CORS network is a stationary, permanent GPS receiver on the ground that collects satellite signals from the global positioning system around the clock. NGS uses these data to determine precise three-dimensional positional coordinates for the CORS sites. And engineers across the country can re-use the same data to position anything else, dams, roads, runways, property corners, chimneys, to a similar accuracy. Today, NGS coordinates a network of more than 1,100 CORS stations that receive GPS radio signals 24 hours a day, seven days a week.

It should be noted, by the way, that some of these stations are mounted on the chimneys of homes around the nation, and they are fine-tuned to accuracies of a few centimeters.

These survey points help make modern maps like dashboard GPS and google earth much more accurate … and could come in handy for anyone else that might need to know the precise entrance coordinates of a chimney.

And Santa will also need to avoid severe weather and electromagnetic storms on his journey. CORS data can help there too.

The CORS network is used by meteorologists to monitor the distribution of moisture in the atmosphere for forecasting severe weather ranging fro tornadoes to snow storms. CORS data are also used by atmospheric scientists to monitor the distribution of free electrons in the ionosphere. This is used to monitor solar and geomagnetic storms. These changes can affect satellites, aircraft, certain radio communications, reindeer-powered sleighs, and even power distribution grids on earth.

Last but not least, the national geodetic survey also administers the aeronautical survey program for the nation. These surveys provide accurate position, height, and orientation information needed for safe air navigation. I think that might come in handy for you know who.


We hope you enjoyed that. Well, you don't need a handheld GPS to find us. We're at You can get more information about the National Geodetic Survey, the National Spatial Reference System, or view current positioning data from the CORS network at

Well, that's all for this week. If you have any questions about this podcast, about the National Ocean Service, or about our ocean, send us an email at

Now let's bring in the ocean ... This is making waves from NOAA's National Ocean Service. Happy holidays and see you next time.