Date: 2005-02-15
To: I HATE DECLINATION !!!
Miles today: 0.0

Well, tonight I took those two certification exams I mentioned in my last post. The State SAR test wasn¢t too bad, so I might actually have passed that one, but I have serious doubts about the outcome of the SMRG Land Navigation exam.         It¢s not just that I have a lousy sense of direction, although that obviously doesn¢t help much. And actually, thanks to the SMRG Land Nav Training Leader (Hey there, Mark!), I¢ve come a long way in my ability to read a topographical map. A few months ago he took me out for a one-on-one exercise in the Prince William Forest and walked me down a stream bed, through the valley and up several draws to give me a better sense of how all those teeny, tiny little brown contour lines on the map compare with the corresponding features on the ground that they are supposed to represent. Then we climbed up to the top of a hill, out onto a spur, and then further down the ridge to a saddle area.         See I even know all those neat terms! Except that, last night during the exam, I had one of my famous memory lapses and couldn¢t for the life of me remember the word ¢spur.¢ Try as I might, it just wouldn¢t come to me. Best I could come up with was ¢finger¢ ¢ and then I threw in the definition (¢an area where the land slopes down in three directions and up in one direction¢) hoping for the best. Of course, it came to me later while I was driving home, but by then it was too late. I¢m sure there¢s a word for that phenomenon, but I...forget what it¢s called. Hmmmm. Is there a pattern developing here?        Anyway, that little ¢ground-truthing¢ exercise with Mark was a real break-through in my land navigation career, and I will always be grateful that he took the time to do that with me. Without it, I would never have passed my field ¢orienteering¢ course later that day. Just imagine: ME ¢ Dr. Lost ¢ alone in the woods, with nothing but a map, a compass, a pace counter, and what little I knew about using those things. To pass, I had to find my way from a starting point (a water tower) to point A, to point B, to point C, to point D, and then BACK to the water tower ¢ all within the allotted time. AND I DID IT!!! Another miracle!!Well, ok, actually, that wasn¢t quite the path I followed. It seems I overshot point C and couldn¢t find it to save my life, so I use a ¢catching feature¢ ¢ in this case a stream ¢ to help me locate point D, and from there it was fairly easy to find point C. Fortunately, the order didn¢t matter as long as I found all four points and made it back in time. The fact that I had to hike at warp speed all the way back to the starting-point didn¢t seem to matter either, and once I caught my breath, I got my card signed off. Yessss!The problem starts when someone wants me to tell them on precisely what course (or ¢bearing¢) I would have to travel to get from point A to, say, Point B.   As soon as they ask me that, my brain starts getting all roiled up, like I was back in grade school again and Miss Owens, my math teacher, was hitting me up with another one of those darn "story questions.¢: Ok, train A is leaving from Boston at 10:49 am and train B is leaving from San Francisco at 12: 32 pm, and Boston is 2,784 miles from San Francisco, and there are 492 passengers on train A, and ¢¦.. well, I¢m sorry. Give me a column of numbers to add up and I can DO that. Heck, give me a twenty year stream of costs and revenues from an investment project, a discount tables book, and an old Olivetti adding machine, and I¢ll calculate you the discounted cash flow rate of return on that puppy so fast it¢ll make your head spin. But don¢t make me have to figure out the calculations like it was some darn ¢story question¢. I hate those things.Where was I? Oh, yeah. See, the problem with compass bearings is that you can¢t trust them. Well, actually, you can trust them; you just have to ¢adjust¢ them a bit. You see, it turns out that the North Pole isn¢t where it¢s supposed to be ¢ at least according to what my compass tells me. It can only tell me where the MAGNETIC north pole is, but that, it turns out, is NOT where the REAL ONE is! And not only THAT, the darn magnetic pole doesn¢t even stay in one place. It keeps movin¢ around. I¢ll come back to that point in a bit, if you¢re still with me. (This is getting almost as bad as that philosophy stuff in Break-a-leg¢s journal, isn¢t it¢¦.Hey, B! Promises, promises!)When they first explained that to me, I was like: ¢Say what??¢ Somebody moved Santa¢s house? Does he KNOW that?? Yup, turns out that he does. And you thought that was just a little ol¢ red light on Rudolph¢s nose, didn¢t you! Actually, it¢s a GPS device, and without it, Santa probably wouldn¢t find his way home much before New Year¢s Eve. No wonder the other reindeer were shouting out with glee. They¢d probably had it by then haulin¢ old Saint Nick¢s butt all over the northern hemisphere trying to find his house when their compasses were all pointing somewhere else ¢ and that somewhere else kept movin¢.   The scientists even have a name for this deviant behavior by the magnetic north pole. They call it ¢declination.¢ You won¢t find it on a road map, because roads are usually pretty well marked anyway. But it¢s on maps like the ones we have to take with us into the back country. Somewhere on the bottom of the map you¢ll find this little line going straight up, and at the top will be a designation for True North. Then there will be a second little line which starts at the same point, but goes up at a slight angle, either to the right or left of the true north line, and it will be designated ¢Magnetic North.¢ The angle between those two lines is called the ¢declination¢ and a precise number is given ¢ say, 5 degrees. Of course, you also have to know how old the map is because, like I said, the darn magnetic north pole keeps moving. If the map is real old, well then, you may not be able to trust that number¢¦.Anyway, if magnetic north is on the left of the true north line, it¢s called a westerly declination, and if it¢s on the right, it¢s call an easterly declination.   From there it is supposed to be pretty simple to figure out a bearing, and to say whether or not that bearing is magnetic or true ¢ and even to calculate one from the other. IF, and this is THE key problem, you can remember when and under what circumstances you ADD the declination to the magnetic bearing, and when you SUBTRACT it, in order to convert a magnetic bearing to a true north bearing. In principle, that shouldn¢t be too hard, right? They¢ve even made up all kinds of little riddles and rhymes to help you remember which way to go. And you know what? Whenever they have to make up a whole bunch of different riddles and rhymes in order to help people remember something simple ¢¦. IT¢S NOT SIMPLE!!! If it were really all that SIMPLE, people wouldn¢t NEED all those darn riddles and rhymes in the FIRST place, would they? HUH?         Actually, it has to do with converting a bearing on a map, where the grid lines are likely to represent true north, to a magnetic bearing that someone out in the woods can follow if they have a compass in their hand. Say, for example, during a search and rescue operation, the dispatcher relays a message from the Incident Commander to a Field Team Leader out in the woods somewhere to move her team from their current location to a new location some 400 meters away on a bearing of 220 degrees ¢TRUE¢ where an important clue has just been found   And let¢s say the declination in that area is 10%. Then the FTL has to know whether to add or subtract 10 degrees from what her compass thinks is 220 degrees to get 220 degrees TRUE. If she gets it right, she should be smack on target. If she gets it wrong, she¢ll be a full 20 degrees off course, and will probably miss the rendezvous. So it can be kind of important.        Frankly, if I can ever figure out declinations, I¢ll be a really dangerous guy. They might actually let me lead a team of searchers some day if I can figure it out. Meanwhile, I¢m trying to rely on memory aids ¢ in my case, it¢s ¢EMPTY SEA, ADD WATER¢. Which stands for MTC ¢ Add W, where MTC stands for ¢Map¢ (which is normally true north) To Compass (which is magnetic), add West. That is, if the declination is westerly, and someone gives you a True bearing, and you want to calculate the corresponding Magnetic bearing, you ADD the declination number. And logically, therefore, going from compass to map, you¢d subtract. Only if it was an Easterly Declination, then you¢d subtract going from Map TO Compass and add the other way around.         Got it? Good. Ok, now, the train leaves Boston at 10:49¢¦..         If I passed that darn Land Nav exam tonight, it will truly be another miracle!Stay tuned,