|How will you use satellite tracking data?|
|First decide what hypotheses
you want to test, like what questions you want to answer. Here are some ideas:
Are these hypotheses correct? If
they are, keep 'em. If they're not, chuck 'em.
Details That You Need
The data deliveries will look like this:BIRD DATE TIME LAT LON
51C 5/5/98 14:39:08 24.435 163.734
Here you have the bird's i.d. (51C), the date and time that the satellites took the location, and the latitude and longitude of the location. These particular data came from a bird that travelled the equivalent distance of around the world in less than 80 days! 51C did it 79 days, and this location came in the middle of that period.
Something that you must understand about the time is that
the 24 hour clock is used, in which 12 noon
Latitude and longitude are like the X and Y axes of the Earth. Lines of latitude run around the Earth east-west. They tell you how far you are from the Equator. O° latitude is at the Equator, 45° N is about halfway between the Equator and the North Pole, and 45° S is about halfway between the Equator and the South Pole. Lines of longitude run from the North Pole to the South Pole. O° longitude is a line between the Poles that runs through Greenwich, England, and it is called the Prime Meridian. As you go east and west from the Prime Meridian the longitude numbers get larger, just as the latitude numbers get larger as you move away from the Equator.
The albatross location data are provided as latitude and longitude measurements, in degrees. To see where exactly the bird was when the satellites located it, you can plot it on a map. Back up at the Hawaii Study you can find maps that you can print to do this. You should have a separate map for each of the individual birds, and you should plot each point as they come in by email to you. If you connect the dots then you will have the path taken by that bird, like we did in the Galápagos Study. When you have those paths, you can easily compare the travel choices of the birds with climate conditions, chlorophyll concentrations, and any other factor that you like.
Check Satellite Accuracy
Figuring Out the Distance
Traveled by the Birds
The Pythagorean Theorem says that a2 + b2 = c2, where a and b and c are the lengths of sides in a right triangle. From the satellite data we can know what the lengths of a and b are, and then we can calculate the length of c. The length of c is the distance that the bird traveled, which is what we want to know. In this case,
the triangle's vertical side a has the length 25 - 23.9 = 1.1
Pythagoras tells us (get your calculator) that
1.12 + 3.22 = c2, so c2 = 11.45 and c = 3.4
We just showed that the bird traveled 3.4 degrees between those two contacts with the satellites. (It might have flown more, if fact, if the bird didn't follow a straight line.) To change the degrees to kilometers, you multiply the 3.4 degrees times 111.3 (the number of kilometers in a degree). To change the degrees to miles, you multiply the 3.4 degrees times 69.2. Now we have our result: the bird flew at least 378.4 kilometers (or 235.3 miles).
There is a slight problem with this method. If you look at a globe, you see that the lines of latitude and longitude are pretty straight near the Equator, so this Pythagoras method works well. But as you get away from the Equator, those lines become more curved and you're dealing more and more with triangles that aren't really right triangles. The Pythagoras method will still give you a result that is approximately correct, but you can get a more exact answer using the "Great Circle Formula:"
Cos D = (Sin L1 x Sin L2) + (CosL1 x Cos L2 x Cos DLo)
Yeah, right... Make it easy on yourself and use the Flight Distance Calculator on The Hawaii Study page. It uses the Great Circle Formula and will give you the exact answer. Compare that answer with what you get from the Pythagorean Theorem. If the two answers are not very different, then you can calculate the flight distances yourself using a2 + b2 = c2, and make your math teacher so proud.
The Need for Speed
This page was last updated on June 18, 1998 11:21 AM