I am practicing taking a bearing and my accuratcy is way off by approx 5 points on the compass.I am using a hand compass and start by pointing to what i know is north then turning the compass to a point of land to the south at approx 190 degrees then when placed on the chart it comes out to 320 degrees... darn! for somthing so simple i am having a hard time getting this right. I like to navagate the bay just by following the compass. but thought it would be nice to learn my position by taking a bearing. once in awhile it comes out right but i dont know what i am doing to get there.I am standing on land and there are no metal objects to disturb the compass.thanks for any help. WJ
- Status
South is 180 degrees. Try that and see how you
do. But why don't you just buy a GPS and not worry about it?
do. But why don't you just buy a GPS and not worry about it?
I have GPS.
But thought it would be nice to have the knowledge. The point to the south is a little of south thats why it is around 190 degrees.. also checked the compass rose on the chart and my compass are the same but the reading still comes off at about 5 points toward the N/E.
But thought it would be nice to have the knowledge. The point to the south is a little of south thats why it is around 190 degrees.. also checked the compass rose on the chart and my compass are the same but the reading still comes off at about 5 points toward the N/E.
Which Compass Rose
Are you sure you are using the magnetic rose and not true? 5 degree sounds about right for the variation at the mid Atlantic latitudes.
Are you sure you are using the magnetic rose and not true? 5 degree sounds about right for the variation at the mid Atlantic latitudes.
5 deg. ?
I’m not too bright, so help me out here. How does a compass reading of 320 degrees against an actual bearing of 190 degrees, come out to a 5 degree error?
I’m not too bright, so help me out here. How does a compass reading of 320 degrees against an actual bearing of 190 degrees, come out to a 5 degree error?
Lines of position
No idea what you are doing from your post. You can not determine you position by just taking compass bearings. In other words in the middle of the ocean what would your bearing be relative to? You need some fixed object to compare against, like a star. On land you should find on a chart some known object, take a compass bearing to that then use a straight edge to draw a line from the known object at the compass angle you observe (you should really convert compass to true, but for now just to learn the basics). Now turn maybe 120 degrees from your previous position and take a bearing on another object and draw another line. Where the two lines cross is about your position. Now do it again and take a third line. There should be a little triangle in the middle where all the lines cross. This is the error in your measurements.You are likely somewhere in the middle of the triange.
No idea what you are doing from your post. You can not determine you position by just taking compass bearings. In other words in the middle of the ocean what would your bearing be relative to? You need some fixed object to compare against, like a star. On land you should find on a chart some known object, take a compass bearing to that then use a straight edge to draw a line from the known object at the compass angle you observe (you should really convert compass to true, but for now just to learn the basics). Now turn maybe 120 degrees from your previous position and take a bearing on another object and draw another line. Where the two lines cross is about your position. Now do it again and take a third line. There should be a little triangle in the middle where all the lines cross. This is the error in your measurements.You are likely somewhere in the middle of the triange.
Compass points versus degrees
This is just a matter of nautical jargon. The four cardinal "points" on the compass rose (i.e. N, E, S & W) are of course 90 degrees apart. Most larger land compasses have 16 labeled "points" (i.e. N, NNE, NE, etc.) which are 22.5 degrees apart whereas large ship's compass roses might have as many as 32 points (i.e. N, NNE by N, NNE, NNE by E, NE, etc.) only 11.25 degrees apart. He must be referring to a 16-point compass rose. Flying Dutchman
This is just a matter of nautical jargon. The four cardinal "points" on the compass rose (i.e. N, E, S & W) are of course 90 degrees apart. Most larger land compasses have 16 labeled "points" (i.e. N, NNE, NE, etc.) which are 22.5 degrees apart whereas large ship's compass roses might have as many as 32 points (i.e. N, NNE by N, NNE, NNE by E, NE, etc.) only 11.25 degrees apart. He must be referring to a 16-point compass rose. Flying Dutchman
Good for you!
Keep trying WJ, compass bearings and plotting can be very tricky. I was a flight instructor for three looong years, and a lot of students had a hard time figuring this out. Even today, I'm surprised at how many new First Officers I fly with that can't work with a Mag compass. Just from what I've read here, let's see if I've gotten things right: the point you're trying to take a fix on was bearing (sitting, relative to you) 190 degrees, or, as you would look at it, a little to the "right" of south. That would mean, if you faced towards where your compass indicated north, the point would be behind your left shoulder. If you were to turn counterclockwise, until you were facing that point, the compass card (the numbers inside the compass) would slowly swing clockwise, until the lubber line across the glass indicated 190 degrees. Here comes the tricky part, sometimes you line up the compass on this point, and the lubber line reads 320. Now, if you imagine north, east south and west as 12, 3, 6 and 9 o'clock, when you face north, or 12, your point should lie close to 7 o'clock. If it doesn't, and it seems closer to 10, then I would guess that YOUR position has changed, and you've drifted towards the south. As you've drifted south, the point you're working with has slowly shifted clockwise through your 9 o'clock, until it's laying off your 10 o'clock position. If you use Dave's suggestion, and draw a line on a chart from that point, at an angle of 150 degrees (the opposite of 320), your position lies somewhere along that radial. To figure out where you are on that radial, you need to take a bearing off another, charted landmark, something big enough that you can easily see it, and it appears on your chart. Point the compass at it, and note the bearing. Let's say it bears 025 degrees, or between 1 and 2 o'clock. Draw another line from that landmark sloping left at 205 degrees. Where the two radials cross, is a rough indication of where you lie in the bay. To triangulate, and confirm your position, as Dave has said, take a bearing off a third landmark, and draw a radial. If the three radials form a small triangle, you've got a pretty good fix. If they all cross at one point, you should run out and play the lottery! GPS is a wonderful thing... Until it don't work. Your mag compass is inaccurate, labor intensive, and archaic, but when the batteries go dead, or the chip fries in the GPS, it'll still work as well as when sailors put their faith in it hundreds of years ago.
Keep trying WJ, compass bearings and plotting can be very tricky. I was a flight instructor for three looong years, and a lot of students had a hard time figuring this out. Even today, I'm surprised at how many new First Officers I fly with that can't work with a Mag compass. Just from what I've read here, let's see if I've gotten things right: the point you're trying to take a fix on was bearing (sitting, relative to you) 190 degrees, or, as you would look at it, a little to the "right" of south. That would mean, if you faced towards where your compass indicated north, the point would be behind your left shoulder. If you were to turn counterclockwise, until you were facing that point, the compass card (the numbers inside the compass) would slowly swing clockwise, until the lubber line across the glass indicated 190 degrees. Here comes the tricky part, sometimes you line up the compass on this point, and the lubber line reads 320. Now, if you imagine north, east south and west as 12, 3, 6 and 9 o'clock, when you face north, or 12, your point should lie close to 7 o'clock. If it doesn't, and it seems closer to 10, then I would guess that YOUR position has changed, and you've drifted towards the south. As you've drifted south, the point you're working with has slowly shifted clockwise through your 9 o'clock, until it's laying off your 10 o'clock position. If you use Dave's suggestion, and draw a line on a chart from that point, at an angle of 150 degrees (the opposite of 320), your position lies somewhere along that radial. To figure out where you are on that radial, you need to take a bearing off another, charted landmark, something big enough that you can easily see it, and it appears on your chart. Point the compass at it, and note the bearing. Let's say it bears 025 degrees, or between 1 and 2 o'clock. Draw another line from that landmark sloping left at 205 degrees. Where the two radials cross, is a rough indication of where you lie in the bay. To triangulate, and confirm your position, as Dave has said, take a bearing off a third landmark, and draw a radial. If the three radials form a small triangle, you've got a pretty good fix. If they all cross at one point, you should run out and play the lottery! GPS is a wonderful thing... Until it don't work. Your mag compass is inaccurate, labor intensive, and archaic, but when the batteries go dead, or the chip fries in the GPS, it'll still work as well as when sailors put their faith in it hundreds of years ago.
A compass rose by any other name...
A hundred years ago, midshipmen had to be able to recite all 32 points of the compass. Now it's even harder, we have to know all 360! Just kidding. If you look at a compass rose on any modern chart, you'll see it's marked in degrees, 360 of 'em. Hmmm... I just re-read WJ's remark about his "5 points" off, and I've figured it out: he's reading the wrong side of the compass card. His landmark is bearing 190, or 10 "points" (degrees) off of south, and his "reading" is 5 "points" to the NE, or 005 degrees. WJ, you're getting a good reading, you're just "reading" it wrong. 005 is YOUR bearing from the point of land, if you draw a line from your landmark, heading towards the upper right (005), you'll have your first radial.
A hundred years ago, midshipmen had to be able to recite all 32 points of the compass. Now it's even harder, we have to know all 360! Just kidding. If you look at a compass rose on any modern chart, you'll see it's marked in degrees, 360 of 'em. Hmmm... I just re-read WJ's remark about his "5 points" off, and I've figured it out: he's reading the wrong side of the compass card. His landmark is bearing 190, or 10 "points" (degrees) off of south, and his "reading" is 5 "points" to the NE, or 005 degrees. WJ, you're getting a good reading, you're just "reading" it wrong. 005 is YOUR bearing from the point of land, if you draw a line from your landmark, heading towards the upper right (005), you'll have your first radial.
Na, just play with the GPS.
I'M KIDDING!!! But don't do like I did once when my GPS was dead. (software problem) I glanced at my cruising guide for a compass course and followed it all day. Problem was, it was the course to follow from Tobago not Trinidad to get to Grenada. Missed the island by 40 miles. When I found out my mistake, well, the cuss words are still echoing off eastern Caribbean islands. But it was crew laziness. I didn't bother to plot a course and my buddy didn't bother to double check a non existent plot. Never again!
I'M KIDDING!!! But don't do like I did once when my GPS was dead. (software problem) I glanced at my cruising guide for a compass course and followed it all day. Problem was, it was the course to follow from Tobago not Trinidad to get to Grenada. Missed the island by 40 miles. When I found out my mistake, well, the cuss words are still echoing off eastern Caribbean islands. But it was crew laziness. I didn't bother to plot a course and my buddy didn't bother to double check a non existent plot. Never again!WJ, Omit step one
"I am using a hand compass and start by pointing to what i know is north" Skip that step, or just look at the arrow on the compass for grins. Fist decide if you are going to determine your position based on true north or magnetic north references. Charts usually have roses for both. I'd stick with magnetic to avoid the whole declination issue and I think all non-electronic binnicle compasses read magnetic. If going magnetic make sure the compass is set on zero declination (forget the needle, just make sure the printed "north arorw" points to zero/360 on the besel. If not there is an adjusting screw somewhere. With declination at zero, point front of compass at a known landmark that is also on the chart. Rotate the bezel so the north arrow outline under the needle is lined up with the needle (and pointed the same way, not reversed). Now forget the needle and take the bearing from the degree mark on the bezel (the top of the compass) that falls on the centerline mark on the compass. Say it reads 92 degrees to center of Browns Point. Now lay your paralel ruler through the center of the rose on the chart and rotate the ruler to 92 degrees on the magnetic circle on the rose. Then walk the ruler across the chart until it hits the center of Browns Point. You are somewhere on (or near) the line defined by the ruler edge. You could be anywhere on the line. To find out where, find another landmark at least 90 degrees off from the bearning to Browns Point. In other words, face browns Pont and stick out your arms to the sides. Find a landmark off to your left or right. Take another bearing and when you transfer that bearing to the chart you will intersect your 92 degree line, but run your second bearing line on the chart about a half mile past or through your first bearing line. Now take a final bearing from any landmark you can find, but at least about 45 degrees on either sie of the first two landmarks. When this bearing is transferred to the chart the line representing the bearing will either perfectly intersect the crossing point of the two other bearing lines (never happens) or miss by a little or a lot. But as previous posters have said, when the three lines cross at different points, a triangle is formed. You are somewhere near the triangle ( of were an hour a go when you took your first bearing). Last "pointer" never place your compass on the chart, you will start to look at it and this you shouldn't do.
"I am using a hand compass and start by pointing to what i know is north" Skip that step, or just look at the arrow on the compass for grins. Fist decide if you are going to determine your position based on true north or magnetic north references. Charts usually have roses for both. I'd stick with magnetic to avoid the whole declination issue and I think all non-electronic binnicle compasses read magnetic. If going magnetic make sure the compass is set on zero declination (forget the needle, just make sure the printed "north arorw" points to zero/360 on the besel. If not there is an adjusting screw somewhere. With declination at zero, point front of compass at a known landmark that is also on the chart. Rotate the bezel so the north arrow outline under the needle is lined up with the needle (and pointed the same way, not reversed). Now forget the needle and take the bearing from the degree mark on the bezel (the top of the compass) that falls on the centerline mark on the compass. Say it reads 92 degrees to center of Browns Point. Now lay your paralel ruler through the center of the rose on the chart and rotate the ruler to 92 degrees on the magnetic circle on the rose. Then walk the ruler across the chart until it hits the center of Browns Point. You are somewhere on (or near) the line defined by the ruler edge. You could be anywhere on the line. To find out where, find another landmark at least 90 degrees off from the bearning to Browns Point. In other words, face browns Pont and stick out your arms to the sides. Find a landmark off to your left or right. Take another bearing and when you transfer that bearing to the chart you will intersect your 92 degree line, but run your second bearing line on the chart about a half mile past or through your first bearing line. Now take a final bearing from any landmark you can find, but at least about 45 degrees on either sie of the first two landmarks. When this bearing is transferred to the chart the line representing the bearing will either perfectly intersect the crossing point of the two other bearing lines (never happens) or miss by a little or a lot. But as previous posters have said, when the three lines cross at different points, a triangle is formed. You are somewhere near the triangle ( of were an hour a go when you took your first bearing). Last "pointer" never place your compass on the chart, you will start to look at it and this you shouldn't do.
stu's got it
omit step 1, and when you rotate you and your compass in hand to point to the landmard, rotate your compass bezel so that mag N matches to the needle or card north. Read the bearing where it says "read bearing here" if your compass has those markings. I taught navigation at the local community college, and the 180 deg error was the first and most common mistake people made.
omit step 1, and when you rotate you and your compass in hand to point to the landmard, rotate your compass bezel so that mag N matches to the needle or card north. Read the bearing where it says "read bearing here" if your compass has those markings. I taught navigation at the local community college, and the 180 deg error was the first and most common mistake people made.
Jonathan knows what i did.. BUT!
I am still doing somthing wrong.I will reread the posts to try and get it right. i am standing on the shore of the bay in front of my house, the shore runs amost exactly E/W.to my sides..Pointing at an island straight out across the water to the south, the island is exactly S/SSE 190 degrees, North is at my back.I am holding the compass with north at north then i rotate the compass and put the N at my target island (Lubberline)the point of needle now reads 190degrees.when i place the hand compass on the chart noth reads exactly north the same as the compass rose on the chart. but my line at 190 degrees shows me being about two miles to the west of my postion. and my target island is about six miles away.even when i do a triaxes from three other points i still come up with a postion about 3 miles west of were i am and about a mile or so south.my chart i am working from including my targets are all within ten miles square..
I am still doing somthing wrong.I will reread the posts to try and get it right. i am standing on the shore of the bay in front of my house, the shore runs amost exactly E/W.to my sides..Pointing at an island straight out across the water to the south, the island is exactly S/SSE 190 degrees, North is at my back.I am holding the compass with north at north then i rotate the compass and put the N at my target island (Lubberline)the point of needle now reads 190degrees.when i place the hand compass on the chart noth reads exactly north the same as the compass rose on the chart. but my line at 190 degrees shows me being about two miles to the west of my postion. and my target island is about six miles away.even when i do a triaxes from three other points i still come up with a postion about 3 miles west of were i am and about a mile or so south.my chart i am working from including my targets are all within ten miles square..
When taking bearings,
the landmarks you are taking bearings from should be at about 60 deg's apart (not in line fore and aft or abeam) If your marks are inline the slightest plotting error can multiply to create more error. Think of two knights jousting. For them to hit the poles end on end, they would have to line up perfect. Any angle and the poles deflect. IHTH Marc
the landmarks you are taking bearings from should be at about 60 deg's apart (not in line fore and aft or abeam) If your marks are inline the slightest plotting error can multiply to create more error. Think of two knights jousting. For them to hit the poles end on end, they would have to line up perfect. Any angle and the poles deflect. IHTH Marc
WJ, you flunk
What did the teacher say? Don't put your compass on the chart. What did you do? You put your compass on the chart. I'm going to send you down the hall to Fred's class, where they just look at GPSs and have pizza parties. "I am holding the compass with north at north then i rotate the compass and put the N at my target island" Don't do that. Do this: I am holidng my compass with the front edge facing the island. I rotate the swivel part of the compass so the little arrow thing that keeps moving around points to 0/360 on the marking on the compass. I read the marking that faces the island and it says 190. OK, now you know you are somewhere on the beach, but where? Since the beach is on the chart, forget taking more bearings. If it is 190 to the island then it is 10 FROM the island to you. Throw your compass in the bay so you will not be tempted to place it on the chart. Put your parcellel ruler on the chart compass rose through the center and through the 10 dree mark and then walk the ruler to the island on the chart. Where the ruler hits the beach is where you are. Note, the most accurate bearing taking compasses are one that have a mirror under the fold down top of the compass so you can hold the thing at arms length and eye level and get it pointed exactly at the landmark and the mirror reflects the compass face so you can rotate it while pointed at the landmark while still at eye level rather than belt level. Question for Mr. Smarty Pants Fred: Your GPS says you are at 47.28.12 and 123.32.12. You see your boat on your plotter. You buddy hails you and says free beer on his boat. You look on your plotter and don't see a little picture of your buddy's boat, you make a mental note to send the plotter back. In desperation you radio him back: "Where are you?" He says: I don't know my GPS doesn't have a plotter but the little number thingies say 47.29.12 and 123.32.12. So what is the distace between you and free beer?
What did the teacher say? Don't put your compass on the chart. What did you do? You put your compass on the chart. I'm going to send you down the hall to Fred's class, where they just look at GPSs and have pizza parties. "I am holding the compass with north at north then i rotate the compass and put the N at my target island" Don't do that. Do this: I am holidng my compass with the front edge facing the island. I rotate the swivel part of the compass so the little arrow thing that keeps moving around points to 0/360 on the marking on the compass. I read the marking that faces the island and it says 190. OK, now you know you are somewhere on the beach, but where? Since the beach is on the chart, forget taking more bearings. If it is 190 to the island then it is 10 FROM the island to you. Throw your compass in the bay so you will not be tempted to place it on the chart. Put your parcellel ruler on the chart compass rose through the center and through the 10 dree mark and then walk the ruler to the island on the chart. Where the ruler hits the beach is where you are. Note, the most accurate bearing taking compasses are one that have a mirror under the fold down top of the compass so you can hold the thing at arms length and eye level and get it pointed exactly at the landmark and the mirror reflects the compass face so you can rotate it while pointed at the landmark while still at eye level rather than belt level. Question for Mr. Smarty Pants Fred: Your GPS says you are at 47.28.12 and 123.32.12. You see your boat on your plotter. You buddy hails you and says free beer on his boat. You look on your plotter and don't see a little picture of your buddy's boat, you make a mental note to send the plotter back. In desperation you radio him back: "Where are you?" He says: I don't know my GPS doesn't have a plotter but the little number thingies say 47.29.12 and 123.32.12. So what is the distace between you and free beer?
Scott! LOL
OK, first off, I haven't used those hockey puck compasses since the service in '67. I have a hand held flux-gate with memory. Second, the devices I use with plotters are all 'slaves' to the chart display on my laptop. All I have to do (as anyone will attest who has PC charting) is drag my cursor around and the LL is displayed instantly for any point on the chart. Besides, I'd just track him down with the radar. Beer is beer! Well, maybe not. I can't mountain sail.
OK, first off, I haven't used those hockey puck compasses since the service in '67. I have a hand held flux-gate with memory. Second, the devices I use with plotters are all 'slaves' to the chart display on my laptop. All I have to do (as anyone will attest who has PC charting) is drag my cursor around and the LL is displayed instantly for any point on the chart. Besides, I'd just track him down with the radar. Beer is beer!
Well, maybe not. I can't mountain sail. It's a tie!
The distance (and course to steer) can be figured in your head from the numbers provided. No electronics needed; one point for Scott. However, the numbers don't tell you whether or not there are any obstacles (rocks, piers, land etc.) in the way, so some kind of chart is still needed. Fred evens the score. Have a nice day. Peter H23 "Raven"
The distance (and course to steer) can be figured in your head from the numbers provided. No electronics needed; one point for Scott. However, the numbers don't tell you whether or not there are any obstacles (rocks, piers, land etc.) in the way, so some kind of chart is still needed. Fred evens the score. Have a nice day. Peter H23 "Raven"
*! OK, Roger's got it, too!
WJ doesn't even have to buy a book, he can look it up online and we can all save our fingers typing in the basics of navigation. Stu PS - WJ, if you put down your hand-bearing compass, and if you have a big Ritchie compass on your boat, just use the main ship's compass for bearings. It'll avoid you ever putting the compass on the chart!
WJ doesn't even have to buy a book, he can look it up online and we can all save our fingers typing in the basics of navigation.
Stu PS - WJ, if you put down your hand-bearing compass, and if you have a big Ritchie compass on your boat, just use the main ship's compass for bearings. It'll avoid you ever putting the compass on the chart! - Status