Navigation, triangulation question?

[Wayland]

Not quite sure why anyone would depend on triangulation anymore, its rubbish and a total false sense of security, if you where doing an ML assessment and using this you'd be laughed off the course mate, this is old text book gibberish....goes like, find 2 or 3 points you can identify on the map to the ground, take bearings from them, intersect...lets stop there !!.. this is the one skill that gets people totally confused and head smashed when trying to do it......if you can identify 2 or 3 points on the map to the ground you are not lost and should be able to ball park yourself to even less than 400metres.

Consider this, when the misty soup is down, what good is triangulation ?? totally useless, I advise you learn to micro navigate and learn to read a map using relief and contours rather than linear features....."the ground never changes" mate

I haven't wasted my students time on Triangulation for decades, there are much better ways off relocating yourself and map reading. When your under pressure, stress, fatigue, injury, illness, etc, you will only remember the simple things.

just my tuppence worth

Fair points but it does no harm to understand triangulation and have it available as another tool if needed.

Before GPS it was a vital tool for finding locations that are not clearly shown on a map. Archeological features springs to my mind but I'm sure there are many others.

Off shore navigation is another good example too.

 

[BushTucker]

Timboggle....Good point, but i have never yet been in such a situation, your guidance and teachings, if you can spare the time, would be most appreciated.

Ammit

 

[jdlenton]

timboggle or jdlenton
Can you tell me more about micronavigation and using contour lines or point me in the right direction please (lol)
I

no probs
this does not cover countour features but its a good start (i use it with the kids a work with)http://www.bbc.co.uk/dna/h2g2/A29848495

it covers most of the key concepts and terminologies have a read and see if it answers any questions or creates new ones then ask away.
most people who come to micronav are doing some of it already but don't realise it see what you think

J*

 

[timboggle]

Guys, firstly though I must point out that it would be best done on the ground, by physical instruction, demonstration, application and review in the dirt - navigation is a practical subject at the end of the day.

If you have a map you should use it, determine your start location, ie, if you just get out of the car and walk willy nilly into the sticks without first of all locating that start point then in my opinon, no skill on earth is going to help you and you deserve all you get.

Use a technique called tick off points, firstly survey your route and identify features that you may identify on that route, small sections at a time, ie, 1 km or so, these features could be anything, linear or ground, ie, boundaries (though these do get moved), stream beds, ring contours (humps) etc, as you pass these, tick them off in your minds eye then refer back to map and repeat - then you allways have a last known point.

Measure this distance and get familiar with Naismith rule, ie, average time and distance covered is around 5 or 4 kms per 1 hour walking on flat ground (depending on weight carried), add a minute for every contour you climb or steep decent - therefore you have cut off points for when to stop walking and re-assess the ground to the map around you, using pacings is difficult over long legs and really should be avoided unless you want to totally crash your brain counting numbers!

Use aspect of slope, how close are the contours in relation to the steepness of ground your walking on, also, what cardinal point is the slope facing, ie, is the slope a northerly facing slope, etc,this skill is your insurance policy when in the mountains.

On flat featureless moorlands you may need to use the compass for bearings - If using bearings, rather than trying to hit a feature dead on from 1 km or so, aim off and use target approaches, something large to the side of your objective or closer to it than you are at your launch point, this helps avoid parallel error.

Everyone can navigate providing your shown how, by someone who knows how - its just that people focus too much on trying to navigate in straight lines and then try to use resection/triangulation as a get out of jail card - in my experience triangulation is a skill used by (don't take this wrongly anyone) people who don't know better, it really is not reliable - if you did it 10 times in the same location I bet you'd end up with 10 differant locations and if your being mullered by the weather you've got no chance whatsover, use the map and use the magnifying glass on your compass base plate to help with the micro detail and do it often, don't be scared of pulling it out in front of friends.

Oh and a myth to bust....if navigating at night, forget the stories about using red light - total nuts, it cancels out the contour lines on the map as these are also coloured red/orange, and over the edge you goooo !!

some navigation resources

http://www.nnas.org.uk/

http://www.amazon.co.uk/Hill-Walking-Official-Handbook-Mountain/dp/0954151100

http://www.mlte.org/index.php

http://www.ordnancesurvey.co.uk/oswebsite/education/teachingresources/index.html

http://www.silva.se/upload/catalog/123_eng.pdf

http://www.silva.se/default.aspx?id=301&epslanguage=EN

Hope this helps so far, I'm away a bit but will look back in here when I can !!

Stay safe

 

[Martyn]

A fix by resection is only as accurate as the bearings you take. The standard Silva type 4 is only accurate to 2 degrees or so. Some compasses are graduated every 5 degrees and are less accurate.

I can get a fix to under 150m if I use a 1:25000 map and a Silva Type 54. This has a sighting unit within the capsule and bearings are accurate to 0.5 degrees.

I guess the Type 15 ranger models with the mirror cover would be somewhere between the two.

If you are sure you are on a known and marked linear feature like a river bank or footpath, then you can get a good fix with just one bearing.

Hey Doc, you ever looked through a Francis barker? The sight picture is very similar to a 54, but it's bigger and even nicer. Seriously.

 

[Martyn]

Hi all

If you want to find where you are on a map, you use triangulation. My question is if and when you guys and gals do this , how close can you get to your true position?

At best I can usually get it to about 400 mtrs!, not brilliant but also using surounding things I am able most times to reduce this to about 50 - 150 mtrs.

What are your experiences with this.

I'm no expert, but doesnt it depnd on the quality of your landmarks?

If you are in the middle of the yorkshire moors, I would think "bombing" accuracy, even with the best compass, is gonna be difficult.

On the other hand, if you are navigating along a handrail - something like a river, accuracy is perfect as soon you hit a bridge.

Anyway, I thought it was normal practice to assume a fairly large level of error and to deliberately aim off to the side of a landmark till you hit a line, to allow for it?

 

[Martyn]

Guys, firstly though I must point out that it would be best done on the ground.....[snipped for brevity]

Great post!

 

[jungle_re]

Aiming off, handrailing and attack points along with thumbing the map are techniques that are easy to use, easy to learn and will increase the ease of navigation. Position finding when visibility is good after a bit of practice is fairly easy to do following the acronym DDCRAPS

DDCRAPS

D – Distance; distance of features on the ground and the distance of them on the map. Are they the same?
D – Direction; moving the map so that identified features are in the same position as they on the ground.
C – Conventional signs; used to identify feature that should be present on the ground which are on the map. I.e. there is a place of worship with a tower on the map can you see it on the ground?
R – Relief; I’m on a big steep hill what’s the gradient where on the map is a similar steep contour pattern? Use the direction of the slope to align to the same on the map. Are there prominent hills or other relief features such as spurs, re entrants or saddles which you can identify?
A – Alignment; using the feature you can identify the distance and direction and align yourself with them will bring your map into orientation and help aid visual feature resections
P – Proximity: The proximity of the identified features will help to establish direction for the orientation. Near/ far general direction
S – Scale; To be able to convert the distance on the map to that of the ground and also to judge features in the distance by relative size to establish distance.

Have a go walk down a path which you identify on the map but don’t follow the map and see if you can orientate and pin point your position using DDCRAPS. Be sure to mark which way you walked up the path then if your unable to gather your bearing you can just follow the path from whence you came. I wouldn't just bin using re sections and intersection (particular intersections) as they can provide a good sanity check to the above if your unsure.

 

[Sleepy Weasel]

Erm, if you know what country you're in, how can you be lost?

Sorry for the flippant remark!

For most of my time out reading a map I find collecting features works for me, resection is just another tool in the navigators' toolkit, as well as all the other methods listed.
One of the biggest things which caught me out on a navigation assesment was the fact that OS maps can be wrong, fencelines move, forests appear or disappear, features are in the wrong place etc.

DDCRAPS sound like a good thing, mights try to remember that sometime!

 

[timboggle]

Erm, if you know what country you're in, how can you be lost? !

nice one, or as Peter Kay said in Max and Paddy, "how can you be lost if you don't know where you" !! lol

 

[redandshane]

Thanks for the info guys
I really need to practise more navigation
Hopefully get a better chance when I go home to Scotland for New Year