Land Navigation with a Lensatic Compass - fast azimuth technique
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- เผยแพร่เมื่อ 16 พ.ย. 2020
- This is a speedy way of using your compass to determine the azimuth between two points. This gives a correct azimuth within 3 degrees and saves a LOT of time fumbling around with a cheap plastic protractor and string.
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Ahhhh thank you, found one of these military looking compass but never knew how to read it. Now it's more clear.
This is a helpful thing which school doesn't teach us.
This is such an important video! I prefer ruggedness over convenience but I was taught with silva compasses and got those because of the ease of working with a map and not needing a protracter. Thank you!
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Holy shit! I was taking all kinds of fire of the SF recruiting BN video of land nav at Mackall. I was trying to teach this and all these guys were talking shit. Glad someone else knows it, thanks alot!
This video made me love my Cammenga compass even more! Not having to bring my protractor is a big improvement and makes it as easy to use as a baseplate compass. I think people are worrying too much about the three degree clicks. Most navigation is done using rough directions and backstops. Only when doing dead reckoning is the accuracy so important. Most compasses are only rated to be within 2 degrees anyway.
This is such a huge help to not have to always fight with the protractor issues. Can we get a video for how to plot points TOO!! Thank you!!
Practical proof that the lensatic compass works perfectly fine with a map, unlike what many people think, or they are eager to sell mirrors to the crowd... excellent video.
Thats a great, clear description of a really simple way to remember.
On a side note.
I recently updated a few of my 25 yr old topo maps for my local area here in Australia
My old maps, as yours there have perfectly lat and long lines.
My new maps, the lines ara a pale blue and sooo faint, even with mglasses on, and under bright table lamp , they are almost invisible. They are disgraceful. A second thing on the new map...no declination diagram. K ust written, ," Mag north ís approx 13.04° East of grid North.
I just spent an hour inking the grid lines on a brand new map.A Romer card would be impossible to use without the re inking
So hard to find who to send some bad feedback to about it.
Anyway, Great video mate 👍🇦🇺
Cheers from Oz
Neil
Would have been really, really nice if Cammenga made their compasses with a transparent bottom and given it rotating alignment lines, just like a baseplate compass. And if instead of the clicking bezel they would have went for a friction one... it would have been the absolute perfect compass.
That was clear and concise, excellent Video! Thank you
Great technique! After doing these adjustments that you demonstrated, all i had to do was to point the magnetic arrow towards the luminous light and voila! Its oriented to my direction of travel.
thanks for the explanation. It is very useful because it gives you azimuth without first having to orient the map. In practice, the Cammenga can be used as a Siva or Suunto type chart compass.
Glad it was helpful!
Exactly how I learned for baseplate compass.
Really easy and understandable 👌👍
Also, if you site something in the distance, like a target. You snap the bezel ring down, it will lock the dial. Then just put the arrow straight north and the 0 on the scale on your position. Whatever you estimate the distance just plot that along the distance scale.
Really love this! Thanks!
With i knew your name. You are very talented!😀 Super job!
I have a small military protractor in my nav kit. As a backup, I carry a flexible half-moon school protractor in my nav kit. Perhaps you can do a video on plotting with a half-moon protractor. I enjoy your videos. Well done.
Great video! Thank you. 🙂
Great info, thanks for sharing!
You did a good job of breaking this down. It this just proves to me I'm incapable of learning how to use a compass after trying for more hours than I care to admit. Frustrating as shit.
If you orient the map first to magnetic north, you can then measure right from point to point. You'll only need to spin the dial once.
do you mean - orient map to magnetic North, adjust dial for declination,
then you'll be able to go from point to point?
@@drd1924 You'll first orient your map so true north on the map is true north on the earth. If your map is recent or if you otherwise trust the declination given, you can just orient magnetic north on the map to magnetic north on your compass. Once the map is oriented, you can stop worrying about declination. To get a bearing, you can read your magnetic bearing on the map and follow that magnetic bearing in the field.
Yup this is the technique I use less steps and easy
This is a fantastic video displaying a practical technique using a lensatic compass. You provide a easy to understand video when determining grid azimuth. I would add a minor thought. When adjusting for declination. If like this example, you fall between either 3 click or 4 and being overshooting by 1 1/2°- just now do this part old school math. Just subtract the declination from the grid azimuth. Then you get the exact adjusted magnetic azimuth. Also good idea to draw a longer line between the two points on your map, now you can slide your compass along the line to get a better visual of your bezel line a matching the map grid lid to aid in lining up the two lines. Excellent excellent video👍 Cheers
Is there still a need to line up the north seeking arrow and the luminous line to find the direction of travel if instead you do the old school math as you stated? So the actual # for his magnetic azimuth is 298.5° since you subtract 300 minus 10.5. In this case we will just use 298° So in this case again is there a need to still orient the compass to the arrows or could you instead just find 289.5 on the compass and walk the direction from that? Also in these cases would it also eliminate the need to click the bezel ring if just doing the math?
@@mr.light7979 Hi Aaron
As you know the bearing you find on a map is your Grid Azimuth. ("Grids" on the Map).
When you now go out in the field in the real world, and shoot a Azimuth with your compass, this is called a Magnetic Azimuth. (Hence compass drawn to "Magnetic" North).
So when you find a Grid Azimuth on a map like in this good video, and you now go in the real world and shoot your Magnetic Azimuth you must compensate for Magnetic Declination.
A great saying I use is :"East is LEAST (Least means subtract) and West is BEST (Best means add).
So lets say you find a GRID azimuth on the map of 300º and the declination on the map for your date is East 10º.
Now when you head to the field and shoot your MAGNETIC Azimuth, you use simple math (more accurate than clicking the bezel). Its Eastern Declination, so you say EAST IS LEAST, so you subtract the declination.
300º - 10º= 290º. So now you shoot your azimuth with your Lensatic compass for 290º and head in that direction.
If you walked on a map you would go 300º but since you walk in the real world you will be walking along 290º
Math is simple and more accurate.
@@PaulHVAC1 just line up your compasses north with you grid north and you wont have to subtract or add right?im not sure cause ive learned this a long time ago
@@PowsangAlaws00 Hi. The only time you would go from grid to Magnetic and Not have to adjust for Magnetic is if you, physically, were close to the Agonic line. But in many applications when you take grid azimuth and then go in the field and shoot your Magnetic azimuth, you will have to adjust for declination.
Very good! Thank you.
Pretty slick, I learned how to do this with having the map oriented to mag north prior to using the straight edge but I see how this could be even quicker.
Yo man, I just posted your video on the special operations recruiting battalion short video on sfas land navigation. I hope you get more traffic
I'm new to this land nav stuff. Curious on a good compass, I have been looking and not sure what is too cheap and what is too expensive. Thanks if you get to this. Great video.
Thank you, very informative....
A simple rhyme to remember as used to be taught in the UK military in my time: from mag to grid get rid (-) from grid to mag you add (+), that way you wont be adding or subtracting the value of the magnetic deviation from grid north the wrong way around, for calculating the back-bearing there is no need to flip the compass around just subtract or add half of the scale, if in mils that would be 3200 and degrees that would be 180, I must confess I have not had to use a compass in anger for 40 years tho :/
Fantastic thanks
Excellent! 😉😁😁
Sweet!
Thanks
Thank you for this video of finding the azimuths with a Lensatic Compass. I want to point out what I noticed because I think I missed understood or missed on something before my question: At about timed 04:40 you confirmed your grid azimuth when you lined the luminous line with the magnetic arrow at 300 Degrees. Then you moved the bezel ring clockwise to get 286 Degrees. But at about timed 08:55, you took the the compass next to the Declination Diagram without having the luminous line and magnetic arrow lined up. Your compass read at about 130 Degrees if I read that correctly. I see that your map is 10.5 on your Declination Diagram. Then the diagram says to Subtract when converting Grid Azimuth to Magnetic Azimuth.
When and how many times I rotate my bezel ring on a compass if I'm either holding it on and off my map? Would I be wrong if I Subtracted the degrees?
Kickass
Sir before you start everything, can you read declination on map adjust it, then proceed, what's the difference to do it after
really well explained, English isn't my nativate language but I've got it despite the fact I didn't in my mother tongue
Thanks!
1.5⁰ difference seems like a lot if traveling further. when you over/undercompensate degree adjustments, would you just slightly change course at intervals to stay on track?
That's a great question. 1.5 can definitely make a difference over long hauls. So, this technique is best used with short intervals (less than 1000m) and plenty of backstops. I don't recommend "dead reckoning" for anything over 500m, especially if the objective is as small as a pole with a number board attached to the top.
Would you be able to do this hack while converting from magnetic azimuths to grid azimuths? Or in other words, while performing intersections and resections? If so would you make a video to show it?
I can definitely do that! When converting from magnetic to grid, after you get your magnetic azimuth (through whatever sighting method you use) simply rotate the bezel in the opposite direction as is shown in the declination chart. Keep in mind that this is not for azimuths that require pinpoint accuracy since each click of the bezel is 3 degrees.
@asimplegenius. Re: Resection/triangulation
If I have sighted a mountaintop, adjusted my clicks opposite of the maps declination diagram/up to date declination, do I place the front edge of the compass on the map mountaintop and rotate the compass until the tritium line is north and aligned with the Eastings? Similar to a baseplate, this would be my location. I would have adjusted for declination and used the compass as a baseplate compass.
Thank you.
I love an old school compass...I was given one of these by my son. Love it! How do we use the magnifying glass? Is it simply toenlarge detail on your map? It looks like it should be some line of sight.... thing!
th-cam.com/video/_TBmCGBqsFA/w-d-xo.html
its to help find the direction of an object you choose
The magnifying glass is part of the sighting method known as "compass-to-cheek." I don't have a video on that, but there are several on TH-cam.
Nice video, man. Thanks for sharing. I guess, basically, you are using that tritium marker like the meridian lines on a baseplate compass? In that case, does it matter if the map is orientated North to obtain correct bearings, so long as the tritium marker is pointing North and aligned with the grid lines? It seems to me that I could have the map facing in any direction to find my correct compass bearing. I picked up a kit of ESSE 'survival' cards and it came with a few business/wallet size map scale cards...and one of them I believe is called a compass rose. It is simply a 360 degree compass dial (thin, flexible transparent plastic card), with a center hole provided for a string. Line up the edge of the card with a grid line, extend the string out tightly in a straight line reaching from starting position to destination and that is the correct bearing/azimuth (East or West declination to be added or subtracted to GN of course). Is this correct? For naval navigation there are several compass roses provided on your navigation charts (aviation charts as well), and those charts/maps do not need to be oriented because the compass roses are already aligned for North with the map. You take all compass bearings from the stationary compass rose, and not moving a compass over the map/chart. I hope this makes some sense! If it does, get back to me to confirm I am correct or incorrect. Cheers!!
Hey Dwayne, thanks for the comment. With many baseplate compasses, the meridian (or declination as I describe here) can be adjusted on the compass itself. It's a semi-permanent adjustment on those compasses. On this particular compass, there is no way to "pin" the meridian. Additionally, when traveling across multiple maps the difference between the map's grid north and the magnetic North changes between each map. So, being able to adjust for that change on-the-fly becomes really handy.
So, you are correct: you do not need to orient your map because, as far as I know, all maps are oriented with north toward the top of the page. As long as the tritium marker (on the bezel, not the one on the North-seeking arrow) is oriented to the top of the page and the compass is pointing in the direction of travel, when you align those two tritium markers it will give you the correct azimuth. As for the compass rose, most maps have a north-pointing arrow somewhere in the legend of the map, which functions the same as the rose. Additionally, I primarily use the plastic card you describe to plot my points. If I'm only in the planning phase (rather than in the field) I will use the string to determine the azimuth.
Thank you so much for this simple explanation! But I do have one question...do you have to be actually on site to take a proper map bearing with a Lensatic Compass? I am practicing plotting bearings (at home) using a map & compass, and checking my numbers with Google Earth; but my numbers are off :( Even when I account for declination.
Not sure what I am, or not, doing correctly. Going from a transparent baseplate (with alignment lines) to a floating dial with degrees, is a learning curve for me apparently.
Learned the same technque in geology course
Could you have just oriented to 289 instead since it's the more accurate direction of travel?
Absolutely: When time and operating environments permit. This is a down-and-dirty "I need to get there yesterday" method. This is for short distances and eliminates writing or remembering numbers. It eliminates most math, which for many people can become confusing very quickly when calculating grid-to-magnetic or vice-versa (you still have to divide the declination by 3 to know how many clicks to move the bezel)
Great info.Thanks.
regardless of what side the mag North is on the GM angle, don't you still use the classic formula like it says next to the GM angle map "To convert a grid azimuth to mag N ADD GM angle?" and subtract for Mag to grid? Even if in your region of the map shows Mag N left of the GM angle Grid North going from Grid to North you would still add? Turn bezel right?
I have a little problem. I didn't understand if you oriented the map towards the north before taking the measurement
Thank you. Very helpful.
This is very helpful! Question: it looks like the short glowing line doesn't match up with the glowing line on the north-seeking arrow. How do you compensate for that? Or is that just the camera angle?
Camera angle i guess
Sir, the lensatic compass used here has graduations of 5 degrees(least count)...how do you set bearing that are not 5 degree multiples...for example say i want to travel at a bearing of 242 degrees using this compass and navigate the terrain?...would an approximation induce error?...thanks
Arrival error= walking distance x sin(error degree÷2) . You want travel 242° and use 240° ; 242°-240° = 2° equation travel distance x sin(2÷2) = for each 100 meters error is 1.745 meters to right, for 1000 meters 17.45 meters. Not much, remember it's almost impossible walk in straight line in forest.
@@janico6 thanks....
@@janico6 Excellent answer to the question! It really only becomes a problem when you're looking for a 10-digit grid the size of a chemlight.
The SIN calculation would be helpful if you received an incorrect bearing from your "buddy." I could see your mate giving you a map bearing as a magnetic bearing and messing up the target. A useful practice is to offset the bearing and follow a map feature to your target. This is not always possible but useful to know which way to turn on the road to find your vehicle.
Why do you have to turn the compass to get north lined up with the luminous navigation line? 4:24
When you line up the short luminous line and the north-seeking arrow, that makes your index line point in the direction you want to travel. It is a fast way to get yourself oriented into the right direction. Did that answer your question well enough?
So it doesn't matter if you have a 1:50k or a 24k or a 62k map, they all are 1000 meter grid lines right, so I can use my milliary protractor 25k scale and get perfect distance and azimuth . I'm I correct in that assumption?
I hope that the last five months someone has answered you. Short answer NO. The quadrille lines are always divided by 1 kilometer in USGS topographic maps. But the scale Define the distances of the objects in it. The azimuth are independent from map scale (scale doesn't matter).
Hi, Casey. You can still use the compass with a 1:25, but you have to divide the numbers on the straight edge of the baseplate by 2 to get the accurate distance (1000m on the bezel is actually only 500m on the map). If you still use the protractor, just be sure you are using the correctly sized cutout. Use the 1:25 for those maps, the 1:50 for those maps, and the 1:100 for... no, nevermind: nobody uses a protractor on a 1:100 map.
Nice job I learned a couple of things but in stead of doing the math with the declaration I learned to make the magnetic grid line longer and use the line to orient the map to magnetic north first this was you don’t have to make any math
where do you get those maps?
Sir, do you orient the map before you do this?
Hi! Sorry I didn't see this before. In this case, you do not need to orient the map. As long as you know where you are currently on the map and where on the map you want to travel to, this method works perfectly.
@asimplegenius I dont get it.. you're supposed to orient the map, north with the compass correct?
@@jdt6450 You certainly CAN orient the map first. It may make it easier for you to feel oriented to your environment. However, it is not necessary, just like you don't need to orient yourself North before using a GPS.
If I were to look for maps that I can use with one, what are they called?
I guess I'm having a hard time finding maps with the grids
Hi Dan, you would be looking for a military map, or a map that uses the Military Grid Reference System (MGRS). The right scale for this particular compass is 1:50,000 ("one over fifty thousand").
@@dansteele4055 it’s been year since you asked this question. But I use caltopo and you can add grid lines to the map. You can select different scaled maps. I use 1:25,000 and 1:50,000 scaled maps. You can either print it on standard size paper or have the company “mountyn” print it off for $10-14 and mailed to you.
If you choose to print your own. Make SURE to size the map to %100 scale BEFORE you print. The grid lines will be to scale of whatever scale you chose. BUT, the distance scale may be off the page. I then will use my protractor to make up my own distance scale. 1000 meter legs. If you have a question for me. Please ask. I’ll do my best to help you through messaging.
💞
It does work great if you have a 50k map. However I’ve never used anything for EIB or land nav other than 25k maps. Never understood why the compass isn’t marked on both sides.
The compass was designed to use on larger areas of traversal. Ultimately, you get four times more visible surface on a map when going from 25k to 50k. When we do land nav, we're not typically moving 20 or 30k. 50k is the nice balance between too close and too far.
AND they say you need a protracted to do this when using a Cammenga Lensatic. Ha! Thank you!
Oh my lord. Just get a base plate compass and save yourself lots of grief.
Update: After taking more time to get into their idiosyncrasies, lensatic compass are every bit as good. Base plate compasses do the heavy lifting for you with declanation conversions but you get the same results with a lensatic with a little brain power added.
I agree that a baseplate compass with adjustable declination is a great tool.... if you're only using one map or not changing areas often. If you traverse over multiple maps, every single one will have a different declination and you will find yourself adjusting your tiny baseplate declination screw over and over. It's nice to have this additional tool in the bag.
You just lost A few students of mine with your video. Lol. I backed it up,and reviewed while watching myself and realized I have a better method of less confusion. So at this point I am highjacking todays video hour and giving the declination class myself minus the video.
Really? Sounds like they shouldn't have been your students to begin with. Where is your video? Unbelievable.
I'm thrilled that someone was using my passion for "video hour"! I would love to hear about your better method that is less confusing; I'm always willing to try something new. Would you mind making a video of your method and posting it?
This is an argument I'd like flat earth peope to explain ... How does a compass work if the world is flat??
Don’t encourage them !
😅
elevation 547, over
So this type of compass is always off a 2 to 3 degrees 🤣
With this *method* it CAN be off up to 1.5 degrees. But more often it's within 1 degree. The compass itself is accurate to the single degree if using a protractor and only the index line and floating dial.
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300° subtract 10.5° will give you grid to magnetic 289° , simple math rather than using clicks.
He states you can do the math if you want or just rotate the bezel. I would want to write down the grid azmith, do the math, write down the Mag azmith, and do the clicks. If accuracy was paramount, I would eliminate the clicks and use my math to get my field azmith.
always always Orient the map first ! ... or forever be lost .
It certainly doesn't hurt... but it is not an absolute rule. I also am not saying to NOT orient your map: it can be very useful when picturing your route before planning your route or taking the first step.
Map orientation isn’t necessary IF using the protractor method for getting azimuths. Is this the rule you may be referring to?
I’m happy you made this video. Good job on it. I always my protractor. But I believe in different methods for emergency contingency plan. P.A.C.E. Stick by it. Lol.
Poor explanation for someone trying to learn
I'd be happy to clarify anything you might not understand.
That was the best video and easiest explanation on map and compass I've ever seen pretty straight forward
This was the least confusing video I’ve seen and I am brand new to this. Also, from your replies to other comments I’ve learned the benefits of a lensatic over a baseplate compass. Didn’t even know the 2 types existed before today.…Thank you!
Thanks