Navigation, triangulation question?

[BushTucker]

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.

 

[spamel]

The larger the grid squares are, the easier it becomes. The more accurate your sighting equipment is, the more accurate it becomes. The more accurately you can plot your lines on the map, the better your final triangulation point. if you use a sighting compass in mils with a protractor on a 1:10000 map then you could potentially get very accurate results.

What you will do in these circumstances is roughly find your position and by taking into account other factors it will be enough to get you back on track. Even if it got you to a 400m square, you'll still know that that corner of the wood half a mile away on a bearing of 240 degrees is that corner of the wood on your map there, so you can easily set yourself straight again. When you need to start worrying is if you are in a featureless terrain such as the desert or the sea!

 

[armie]

I do this, but not very often.
My best result must have been less than 40 metres, in the Moselle valley. I was pleased with that, but the river banks we were on were so steep that we still didn't know which footpath we were on.
My worst result was about 250 metres, triangulating while sitting comfortably outside a pub! I blame the metal in some nearby bikes ... or perhaps I looked at the wrong church tower

 

[spamel]

The more reference points you have, the better your result will be. Both Scott and Amundsen had to take numerous sightings of the sun to ensure they were at the South Pole. I believe Scots' team spent 24 hours making sure they were in the right place. Obviously, a compass is totally useless at the poles as it wants to point straight towards the ground! And there isn't much to take a bearing from to triangulate your position with so they had to use the sun and a sextant with the ridiculous amounts of maths required to get a positioning. A least they only had to work out Latitude!

 

[jungle_re]

Very much dependant on the objects you use to sight on and ther placement. You want an even as possible distribution so the cut lines split the area evenly. You should have no problems getting a fix of 100m on a 1:50K which is the accuracy of the base map anyway if you are able to chose good reference object and correctly locate them.

 

[jungle_re]

The more reference points you have, the better your result will be. Both Scott and Amundsen had to take numerous sightings of the sun to ensure they were at the South Pole. I believe Scots' team spent 24 hours making sure they were in the right place. Obviously, a compass is totally useless at the poles as it wants to point straight towards the ground! And there isn't much to take a bearing from to triangulate your position with so they had to use the sun and a sextant with the ridiculous amounts of maths required to get a positioning. A least they only had to work out Latitude!

Or a theodolite and use the stars and sun. Astro obs with a theodolite arnt easy and the maths is a long winded one and you also require an uptodate star almanac. It requires special surveyor training but is not beyond the bounds of an averagely inteligent person.

 

[spamel]

Or a theodolite and use the stars and sun. Astro obs with a theodolite arnt easy and the maths is a long winded one and you also require an uptodate star almanac. It requires special surveyor training but is not beyond the bounds of an averagely inteligent person.

Indeed, but I believe they had sun all day long by the time they had hit the pole. I'm sure they did take a theodolite though, astral navigation intrigues me!

 

[Wayland]

I've only ever had to do it once after coming out of a big plantation on the edge of a moor.

Nothing visual to fix on close by but two other woods in the distance. I used the edges for triangulation.

I couldn't tell you exactly how accurate my fix was but a bearing from there put me on a line 20m from the archeological site I was looking for, which would have been a swine if I'd missed it.

 

[jungle_re]

Indeed, but I believe they had sun all day long by the time they had hit the pole. I'm sure they did take a theodolite though, astral navigation intrigues me!

The theodolite would enable fair more accurate readings of azimuth than the sextant which when dead reckoning over great distances would make a remarkable difference.

Astro is less intriguing when your sitting in the cold trying to hand bash the obs in the middle of Jan trust me lol. But glad i did it as its not taught on any modern surveying syllabus anymore.

 

[Doc]

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.

 

[Kerne]

I used to do this all the time when I was sailing but I think that I can honestly say that I have never had to do it in earnest on land. If the visibility is good enough to be able to pick out three distinct landmarks, then it is usually good enough to work out where you are using other map data. However, I often take a bearing off an object to know how far I am along a linear feature - not quite triangulation in the strict sense.

 

[jungle_re]

Thats a liner intersection

 

[bushscout1]

I do this, but not very often.
My best result must have been less than 40 metres, in the Moselle valley. I was pleased with that, but the river banks we were on were so steep that we still didn't know which footpath we were on.
My worst result was about 250 metres, triangulating while sitting comfortably outside a pub! I blame the metal in some nearby bikes ... or perhaps I looked at the wrong church tower

Armie

Are you sure it had nothing to do with the contents of your glass?

 

[timboggle]

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

 

[jdlenton]

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.

I was about to say the same thing myself. Single, Double and triple point resections are an interesting thing to do but not to depend on. As has been said learn to navigate using contour features, bearing and pacing+time (dead reckoning),

J*

 

[armie]

Armie

Are you sure it had nothing to do with the contents of your glass?

Hmm, quite possibly. I'll investigate and compare results.

 

[redandshane]

timboggle or jdlenton
Can you tell me more about micronavigation and using contour lines or point me in the right direction please (lol)
I am attempting to increase my navigation skills and agree entirely with what you said because thats how I usually do it when I can see things.
However I fancy there will be a time when I cant
In fact there has but I have been kind of lucky

 

[DavidJT]

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.

What he said.
Also use a type 54, and take a quick bearing often, and then relate that to surround features. Only should need to triangulate on very barren featureless terrain (moors etc).
I think this type of navigation is an important skill to learn though.

 

[timboggle]

redandshane
not a problem mate, will come back with some tips and resources over monday/tuesday on this thread,

Only should need to triangulate on very barren featureless terrain (moors etc).
QUOTE]

DavidJT
What features do you triangulate off on a barren featureless terrain mate ??, seems to contradict itself mate

 

[DavidJT]

redandshane
not a problem mate, will come back with some tips and resources over monday/tuesday on this thread,

Only should need to triangulate on very barren featureless terrain (moors etc).
QUOTE]

DavidJT
What features do you triangulate off on a barren featureless terrain mate ??, seems to contradict itself mate

Distant ones!
But your points in your first post are very good, and well made.