Can you tell me how to get to 9ºN?
December 11, 2007
Right now we are on open ocean. There is no land to be seen, and virtually no surface animals either. There is the occasional bird, and we have been fortunate to spot a few flying fish, dolphins, and a couple of sea turtles. Nevertheless, the area is quite remote. It certainly is beautiful, but a bit disorienting. It’s strange not to see land. Despite my uncertainty, the ship knows exactly where we are.
What is unusual for those that have never been at sea is understanding our location. I found it challenging to tell people where I was going before embarking on this trip. People are often used to giving directions based on visual cues (for example, “its across the street from the grocery store”, or “turn left at the snow board shop”). But at sea, there just aren’t those types of cues. The best I can do is tell you that we are over the East Pacific Rise (a geologic feature on the ocean floor) and our coordinates are 9º50′ North, 104º West.
When the Chief Scientist planned this research expedition, she gave the Captain of the Ship the coordinates for the location she wanted to go. So in my head popped a big question: how does the ship find the location? I had a chance today to speak with PJ Leonard, the Ship’s Chief Mate (in the picture on the right) who was kind enough to show me one of the most interesting parts of the ship, the Bridge. It really is the nerve center of the ship as this is where they control the ship. Located on the Bridge is the ships elegant system of navigation through the use of GPS (Global Positioning System). But this isn’t quite the same as your automobile’s GPS - its more complex.
Like the system you might use at home, the ship’s system relies on 3 of the 24 satellites orbiting the Earth to get a signal. Through triangulation, a location is determined. The ship, however, doesn’t just use a single GPS, it has a dynamic positioning system that uses three GPS units (each of which uses 3 satellites), then calculates the average of the three to get a better fix on location. (Ah… nothing like repeating trials to increase confidence in the results!) The dynamic positioning system is so sophisticated that it virtually runs itself and even has a 14-hour battery back-up in case the ship looses power. The ship is able to attain somewhat better accuracy than a GPS you might purchase however, because integrated into this system is a differential GPS called CNAV that corrects the inherent errors in GPS improving accuracy to within 1-3 meters!
To assist the GPS, the ship has three gyros that are like fancy compasses (see image on the left). Two of these gyros measure the Earth’s rotation, and one acts as an accelerometer to provide information on altitude and motion on an axis. The ship also uses radar technology to determine its distance from other objects (right now, the only other objects showing up on radar are clouds!) Finally, there is one other piece of sophisticated technology that the bridge uses. It’s so important that PJ wanted to make sure I told you about it. It’s satellite radio, so the bridge can have music accompany them during their shifts. Sadly though, we are now too far south to pick up on the signal. Perhaps I’ll loan him my iPod for a while!
After getting acquainted with the instruments on the bridge, I am left wondering how all of this navigation was done before we had GPS, dynamic positioning systems, radar, and satellite radio. Likewise, if these electronic systems fail (which PJ guaranteed to me that they wouldn’t… should I believe him?) how will the ship navigate? I know that in many cultures, traditional navigators could reach far destinations with amazing accuracy without the use of even a compass. How did they do it?
So my question to all of you out there is the following: assuming we didn’t have such advanced technology, how would one navigate a ship?
December 14th, 2007 at 2:52 am
Hi Mrs. Grace,
Noor here. I hope you’re having loads of fun at sea!!
I wanted to answer your question about navigating in the ocean without using advanced technology.
If you didn’t have technology like we do today, and you were lost at sea, one of the best ways to navigate would be by using the stars in the night sky. The North Star, now Polaris, is the best used for navigating northward. It is found at the end of the “handle” of the Little Dipper and is very bright. So, if you were at, let’s say, 30 degrees latitude, the angle to the North Star would be about 30 degrees. A complicated way to say that is at any point north of the equator the angle from the horizon to the North Star (its altitude) is the same as the latitude from which that angle was taken. Right now, there is no “South Star” as useful as Polaris. The star Octanis is closest to the south pole, but is very dim. However, the constellation Crux, the Southern Cross, points towards the south pole. So, basically, the North Star would be used like a compass. This is how our ancestors traveled way back when!
Hope this helps! We miss you at school!!
December 17th, 2007 at 11:29 pm
Hey Mrs. Grace,
How is you cruise going? We saw that there was a storm coming you way and in your latest blog you must have been talking about it.
I’m here to hopefuly answer your question:”Assuming we didn’t have such advanced technology, how would one navigate a ship?”
In the 1800’s you might see a captain useing a sextant. A sextant is an instrument that is used to measure the angle of celestial objects (also known as stars) above the horizon. Useing mathematical formulas and a watch they could tell where they were.
They could also use celestial objects (also known as stars) to see what direction to go. In the Northern Hemisphere we use the Northern Star or Polaris. In the Southern Hemishere they use, as Noor said, the Southern Cross.
Hope to see you soon,
Austin W.
P.S. I hope you get to dive in Alvin.
January 8th, 2008 at 1:08 am
Mrs. Grace,
When posed with that question, all I can do is remember in the days of old when sailors looked for the stars for guidance. Yet, stars have one flaw for those that need extremely accurate positioning-they move. One must be able to have a rotating star chart that is accurate up to that very hour to be able to use the stars for extremely accurate guidance. Let us say you did not have a chart like that or that the sky was cloudy. Then what would you do?
I believe a simple compass should be accurate enough when cross checked with something else. That something else would be a map. As soon as the ship leaves the harbor (or the place it was docking) one could use a distance formula were you use your rate (speed)* and time (how long you have been out) to find how far you have traveled. When you put down how far you traveled on a map, you can see were you are. Yet to make sure you stay on course, you would have to get a compass and know exactly what direction you would be going in. Although, to make sure that everything is all right, you would have to make sure your map is accurate.
Anyways, that is my answer. Using the stars, a map, and compass, I think one would be able to navigate a ship accurately. The different methods would check and make sure that you are going the right way.
Sincerely,
Natty
*you would find your speed by doing a simple experiment with throwing bread in the water and seeing how long it took for it to travel the length of the ship. (You would need to know how long your ship is also though.)
January 10th, 2008 at 5:23 pm
In the time before technology, sailors navigated in many different ways:
1. Stayed in sight of land and used known landmarks to judge where they were;
2. Did depth soundings (a certain number of fathoms deep meant the ship was a certain number of days from a particular port or landmark);
3. Ancient sailors used the sun and star positions to determine where they were;
4. In places where the stars were below the horizon (like the very far North) ancient sailors watched birds to determine how close they were to land. A bird with a mouthful of fish was heading towards land, an empty mouth usually meant they were flying from land. Some sailors took crows with them and kept them very hungry, releasing them and watching where they went, knowing they would fly towards land to find food.
5. Some ancient sailors studied the waves, tradewinds and currents.
6. Devices such as the sundial, astrolabe and compass helped sailors determine their position.
January 11th, 2008 at 5:02 am
Hi Mrs. Grace,
All the cars, ships, airplanes, and hand held devices have GPS systems but there are only 24 satellites so it seems like they are being over worked. Being that far north, I’m surprised you weren’t too cold to write these journal entries.
In response to your question, star gazing was probably the most common. But, that probably wasn’t that accurate. Sailors used tons to measure the angle of the noon sun but that was inaccurate because the sun changes heights during different seasons. Maybe they just never knew where they were. After all they didn’t know that America existed in the middle of the ocean.
A lot of early navigation was done by following the coast line. As long as they could keep track of their speed, it was easy enough to get accurate measures on continents. Columbus was one of the first to open an ocean. Magellan was the first to sail around the world but his biggest priority was to keep going west. When he had the chance he followed the coast line too. I hope I answered the question.