I received a request to describe the “grid” used here for aircraft navigation. It’s a very foreign concept to those of us in the aviation business. My goal is to keep it simple and hopefully short so you won’t use this as a substitute for your daily sominex.
The first problem you run into as you near the pole (north or south) is that all the lines of longitude (the ones that go north and south on the globe) converge at the poles. Simply that means that at the equator the lines are the furthest apart and small navigational errors can be overcome. As the lines approach the pole they come closer and closer until they touch meaning a small navigational error can have significant consequences. Think of the lines on a basketball as you picture the lines of longitude.
The second problem is that the “magnetic pole” and the “geographic pole” are two different places. (Not bad you say but consider that the magnetic and geographical poles are almost 1000 miles apart here)(Actually the magnetic pole is not even on the Antarctic continent). Further, in the early days of aerial navigation pilots used a magnetic compass to navigate. So by using his compass only, the pilot, without correction, could never get to the geographic pole. (the place everyone wants to go) Because the poles are so far apart celestial navigation became the preferred navigation. (This is the same type of navigation used by Christopher Columbus on his way to the new world) It would be a little like using a slide rule (if you can even remember what one of those is) instead of a computer for navigation.
To further complicate the issue the magnetic pole is always moving so charts must be regularly updated with the current location of magnetic south as well as the annual rate at which it is moving. (Are you still with me?) So now picture those lines on the basketball not meeting at the bottom but somewhere on the side and always moving.
This problem was first noticed when working around the North Pole. The North Pole was first explored because it was easier to get to because you didn’t need to cross huge bodies of water in primitive and unreliable airplanes. (Also, I think they were really looking for Santa Claus and they knew he didn’t live at the South Pole). Also pilots don’t carry their maps is the shape of globes but rather as flat maps like you would use on a road trip (unless of course you’re using your computer or a Garmin Navigation System).
Finally someone, in a fit of genius, said lets just draw our own lines of navigation on the flat map with the geographic pole as the center and make the lines of longitude and latitude the same distance apart, parallel to each other, not coming to a point, much like the street layout in Salt Lake City where everything is neatly organized around the Mormon Cathedral in the center with streets going out, in squares, north, east, west, and south. (This is getting a little long. You might want to pause here for a brief nap to refresh your brain cells)
What really made this grid navigation possible was the advent of computers in the cockpit. This new grid system could be programmed into the navigation system of the airplane so the pilot didn’t then need to make accommodation for all the whacky stuff descried above. If you wanted to go north to the pole you flew north. If you wanted to go home you went south. Easy, everyone was excited. (Take a moment here for a quiet cheer; don’t disturb the babies or the neighbors though)
If you know Rodney Dangerfield you will understand this next paragraph. Even though the Antarctic Continent is much, much larger than the Arctic and arguably much more important in its affect on our global environment it was treated like Rodney. It got no respect when it came to the use of the grid map. Gobbledygook you say get to the point. Interestingly they just took the same grid map used for the North Pole without making any accommodation for the fact that the South Pole is on the other end of the globe. Hence when you are flying to the South Pole your navigation equipment tells you that you are going north, ala the North Pole, and visa versa. Is that all clear as mud now?
It really is a good system unless you work in the control tower where they must deal with airplanes that have these fancy computers and helicopters which don’t. So here at McMurdo, when a fixed wing airplane calls in to say he is north of the airport and a helicopter calls in to say he is south of the airport they are both approaching from the same direction. You can see the problem. For the pilots it’s a great system for the control tower folk not so great. The good thing is there are two square lights in the ceiling of the tower cab. One is grease pencil marked for grid directions, the other for true (magnetic) directions. So when you see a controller looking at the ceiling of the tower he is not rolling his eyes in disgust, he’s just checking to see which direction you’re coming from.
So that’s it. Aren’t you sorry you asked? For more information on this (which I suspect you will not want) talk to me when I get back.
I’ve still got it. I can still make a short story long!
