# USING THE COMPASS WITH A MAP

 "Look at this map, Lou! You'll notice that as well as showing the villages of Luluville and Louberg and the larger market town of Ipple, the map has a compass rose printed on it! AND VERY IMPORTANT, LOU: notice that the N (north) on the compass rose points towards the top of the map!"
 "Is north on all maps towards the top?"
 "On most maps it is - even if they don't show a compass rose or a North arrow! If north on a map is not towards the top, there'll be an arrow to show you which way it is!"
 "Cool! But c'mon, Lulu! 'Luluville'! 'Louberg'! 'Ipple'! Where'd ya get those names from?!"
 "Concentrate, Lou! OK? Back to direction! As we said, to know which way to go from one place to another, all you have to do is know its azimuth or its compass quadrant bearing! For example, the azimuth from Luluville to Louberg is 45 degrees! That is, the line from Luluville to Louberg trends in the same direction as the line from the center of the compass rose to the 45 degree mark! Or, also as we said, we can call it N 45° E!"
 "Let's see if you understand! Go try out these PROBLEMS in determining directions on a map!"

 "Great! So I know the direction from one place to another on a map! But there I am standing in Luluville with my map. I know the direction to Louberg is 45 degrees or N 45° E. But I don't see any signposts saying '45 degrees, this way'! What good does reading the map do me?!"
 "Here's one way! First, suppose there's a feature you can see on the map that you can also see from where you are standing in Luluville. It could be a road, a building, a river, the top of a hill.... For example, suppose from where you are standing you can see the bridge (shown in GREEN) that crosses the River Taff. Now look at the map. Draw a line from where you are to the bridge (the short, RED arrow). Now see which direction on the compass rose is parallel to that line. It's about 78 degrees (N 78° E). So, the angle between the direction to the bridge (78 degrees or (N 78° E) and to Louberg (45 degrees or N 45° E) is about 33 degrees (78° minus 45°). Now all you have to do is face the bridge, turn about 33 degrees counterclockwise, and start walking!"
 "These boots are made for walkin', I suppose!"
 "Why not?! Let's try you out. Dig this PROBLEM on using a map to find your way!"

 "OK, I got that. But isn't there an easier way that doesn't involve estimating angles?"

 "You could use a COMPASS with your map!"

 "A compass has two important parts to it. First, it has a face with a compass rose imprinted on it. Second, it has a magnetic needle which, when the compass is held level, floats freely over the center of the compass rose. The needle rotates until one end (the black end in this case) points to magnetic north and the other end (the red) points to magnetic south!"

 Now, press the button to see what happens when I turn the compass!

 "You can see that even though the compass itself is turned so that the North arrow printed on its face points to different directions, the black end of the floating needle always keeps pointing in the same direction! Towards magnetic north!"
 "But remember! North annd magnetic north are usually not in the same direction! You have to take into account the angle between true north and magnetic north! That angle is called the magnetic declination!"
 "Seems crazy to me! So what good are all the directions printed on the face of the compass?! The needle keeps pointing in the same direction, but it looks like the directions on the compass rose can point in any direction - depending which way you point the compass!!"

 "Keep the faith, Lou! I'm gonna show ya!! Let's look at our Luluville-Louberg map again. This time, instead of showing the whole compass rose, the map just shows true north (N), magnetic north (MN) and the magnetic declination! And I've added a green arrow to show where you want to go - from Louberg to Luluville!"
 "OK, you're standing in Louberg! You place the map on a more or less flat, level surface! You then place the compass on top of the map! The black end of the compass needle points to magnetic north! That's the only thing you know is pointing in the right direction! The N and the MN on the map are just pointing the way they are because of how you happened to place the map! The same holds true for the directions on the face of the compass! They point the way they do because of how you happened to set the compass down! But don't forget, the needle floats free of the face of the compass."
 "So you need to make the directions on the map and on the face of the compass mean something! What you do is place the compass on the map so that the 'N' on the face of the compass is parallel to the north arrow 'N' on the map! (If the top of the map is north, as it is for most maps, then the top (north) edge of the compass is parallel to the top (north edge) of the map!) Then, you rotate both the map and the compass together until the Magnetic North (MN) arrow on the map points in the same direction as the black end of the compass needle! The black end of the needle now points to 25° (N 25° E)! (That's the magnetic declination!) Now, both the map and the compass are oriented properly! That is, everything is pointed towards where it says it's pointed: the North arrows on the map and on the compass face point true north; the black end of the needle points to 25° (N25° E), which is the direction of magnetic north!!"
 "Now, we look to see what direction on the compass rose is pointing in the same direction as the green arrow from Louberg to Luluville! It turns out to be 225° (S 45° W)! In the diagram, I've drawn a short green arrow on the compass rose to show you that that direction is indeed parallel to the green arrow on the map! So, Lou, all you have to do to get to Luluville, is to make sure that when you start off (and keep checking as you go along) the black end of the compass needle points to 25° (N 25° E); and you head towards 225° (S 45° W) as shown on the compass face!"
 "I feel positively empowered! Now, with a map, I can find my way anywhere!"
 "You've made good progress, Lou! Now go to the Toolbox Menu and check out 'Latitude and Longitude'!"