Exactly what is triangulation?

[cutsandbruises]

I keep reading on the post about averaging waypoints to make sure the coordinates of a placed cache is correct. I understand that but I don't understand what is meant by triangulation or triangulate... I'm sure its some geometry thing with angles no doubt.. Just a simple explanation might help all us newbies.

[+OneOfEm]

It's explained on one of the FAQ pages...

 

Look here

[Aksor+Raskol]

Hey C+B, did the link help? Basically, you're using your GPS on the BEARING function to get a reading of say; 260 degrees and 50' away. You set the ring on your compass to 260 degrees, align the needle with North and site down the line. Mark an imaginary line to the distance. Now move to another location at right angles and shoot another bearing of say; 180 degrees and 80' away. Your "target" is where the 2 imaginary lines intersect. Practice makes perfect! Try it on the next few caches you've already found just by using the GPS to get a feel for it. Good luck

[+Chipper3]

In the context of geocaching, triangulate means to identify the location of a WP by:

 

1. Go to a location say 100 feet from target. Obtain a bearing to target from your GPS. Use your compass and site along that bearing and create a "line." I have seen this doen with string but you are looking for a visible reference like a big tree or rock.

2. Repeat from a 2nd point about 120 degrees from the 1st.

3. Repeat from a 3rd point about 240 degrees from the 1st.

 

Where lines all intersect will be the target.

 

Triangulation was used a lot to pin point the location of hidden radio transmitters. Instead of a GPS, a highly directional antenna was used to establish a bearing. where the lines crossed was where teh 'spy" was located.

[+Olar]

A+R and C3 have both described it perfectly. One thing I would add is to be sure and allow the GPSR to settle down at each of the spots where you are shooting a bearing. Usually a minute or less is enough. Its amazing how accurate the process can be, assuming the original cache coords are correct, and often just one bearing line is all you need.

Sure beats trying to follow the whirrly-bird direction needle when hunting a well hidden cache.

 

Happy Caching, Olar

 

"You are only young once but you can stay immature forever"

[Aksor+Raskol]

Olar is right. I won't get bogged down by an erratic GPS for more than 10 minutes before the compass comes out and I'm shooting bearings. Works all the time.

[+Sunnydae & Co]

Wow, I never knew this. What helpful information! Thanks

[Aksor+Raskol]

For further clarification, the reason this works is most GPSr's pointers are only accurate when you are moving/walking. As you walk, especially in heavy tree cover, the GPS is dropping satellites and acquiring new ones all the time, depending on what birds in the constellation are "visible" at the time. If you are a long way from your intended target it matters little as the pointer will still point you in the general direction. But as you narrow in on the cache the GPS can't keep up with all the information and becomes confused and starts spinning the pointer around. If you stop and let it lock on the satellites, your direction pointer becomes useless, but the GPS still knows which way the cache is and how far away it is. Switch over to bearing and it gives you the data in degree format instead of trying to convert it to the pointer. If you take one bearing and it tells you it's 123 degrees at a distance of 100 feet and your accuracy is 40 feet, the cache could be anywhere along that imaginary line from 80 to 120 feet. Move to the side and take another bearing and you've just increased your accuracy by 100%. Ta! Da! Cache found

[Aksor+Raskol]

Oh, and although no one mentioned this, you do need a compass. Anything with a rotating degree ring and a site line will do. No need to go overboard here. A $10 Silva works just fine. You just need to get a general idea of the bearing, not etch a lazer line. And like I said before, go back to one of the caches you already found in an open area and practice. Or use a stump or rock in your back yard, field, park, etc. Mark a waypoint and pretend there's a cache there, then triangulate it from several directions

[cutsandbruises]

Thanks for the info.

I think I better go buy a compass.

The last cache I did I looked for 20 minutes because my needle on the GPS just kept spinning as I got closer and I was in heavy tree cover.

Every time I go out I learn something new..

Thanks again...

[+w5waf]

I wonder if anybody has tried to plot the coords of a cache on a quad sheet and then try to locate it using only a compass and a map. Think I'll try that.

 

Bill-W5WAF

[Tahosa and Sons]

Check this page

 

Tahosa - Dweller of Mountain Tops.

[Kerry.]

quote:

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Originally posted by cutsandbruises:

I keep reading on the post about averaging waypoints to make sure the coordinates of a placed cache is correct. I understand that ....

---

 

but are you sure? you understand averaging.

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[cutsandbruises]

yes I understand averaging. I read it on one of the FAQ pages. Thanks for your concern.

[Kerry.]

quote:

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Originally posted by cutsandbruises:

yes I understand averaging. I read it on one of the FAQ pages. Thanks for your concern.

---

 

And you still use it then?

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[ccarrara]

Hey Kerry,

What are you doing over here?

 

Maybe you can help on the discussion in the electronics section of THT regarding GPS startup times. See the thread "Best GPIRB..."

 

Regards,

Birdman

[Kerry.]

quote:

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Originally posted by Birdman (The real one):

Hey Kerry,

What are you doing over here?

---

 

Been here for quite some time, trying to keep em honest

 

Shall see what's going on at the THT next.

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[+Brian - Team A.I.]

Myself and a few other caching teams used 3 GPS units to triangulate the triangulation, as it were. The 3rd stage in a multi on a rocky hillside gave us all fits. We searched for it (5 sets of eyes) for a good 45 minutes. It wasn't until we each took a side and headed where all the units pointed and we found it instantly.

 

Brian

Team A.I.