Trig points - a general discussion

[Richary]

I've deliberately left some of the local trigpoints as unfound. Why - because sooner or later (like tomorrow) I need to find a cache to round out the found every day of the year stat. So if I don't get a real cache tomorrow I can stop and take a photo on the way home!

[pjmpjm]

I've deliberately left some of the local trigpoints as unfound. Why - because sooner or later (like tomorrow) I need to find a cache to round out the found every day of the year stat. So if I don't get a real cache tomorrow I can stop and take a photo on the way home!

But I thought our beloved trigpoints WERE real caches . . .

Must ask rogerw3 and Yurt about this . . .

Next people will be talking about Santa Claus . . .

[rogerw3]

What? Trigs not real caches, what next? Stories about the Tooth Fairy, the Easter Bunny or even Gnomes not being real.

[Richary]

Well, there is less rush about trigs, as they are likely to stay there for a while. Also are easy finds. But I did find a very nice cache by Rainbow Spirit this morning while out on a job so that ticked today off. If I'm away from home I will certainly be grabbing trigs as I pass them.

[Tuena]

Easy finds? Some are, some aren't. Some are quite difficult terrain wise, others are so thickly surrounded by scrub that when you finally get there, you can't see them! Have two such Trigs on my (mental) list - one on the Nerriga Rd appears to be only a few metres in but the scrub was so thick I was forced to a standstill. The other is above Berry but being in a NR you can't go off track. May be able to walk along the cliff tops but these are intersected by gullies & scrub. Not easy.

[Richary]

That's true enough, but the ones close to home I leave for emergencies are all in suburbia and generally on water tanks. The cache Mt Royal Run up in the Hunter has a TP at the top of the hill, but the surrounding vegetation is so high and thick you wouldn't see it until within a few metres. Unluckily I don't think I photoed the trig when I did the cache a couple of years back. Was too busy dodging leeches!

[If]

Trig points are a nuisance
Several time now I have been happily wandering from one geocache to another when somewhere, just on the edge of the GPS screen, a trig point symbol will briefly appear.
Suddenly all thought of finding the next Eclipse tin hidden in a guard rail on the side of a busy main highway evaporates and I'm off on another crazy chase through the wilderness to try to get to the top of a mountain
If I get to that Eclipse tin later in the day without any scratches, leeches, having to unbog the geomobile or running out of daylight and having to set up camp halfway up the mountain I consider myself lucky
Ban the trig !!
They are too much fun

[landau351]

Hi guys,
I see that this discussion appears to cover Survey and Bench Marks as well as Trig points. I created TP5618 thinking it was a Trig, but had it archived as it was only a Survey Mark. So a few questions to the experts:-

• Are their instructions anywhere on GCA that explain what is a Trig, what is not, and how to list/log them?
  Do Trigs always have the quadripod above?
  Can a Trig have a Survey/Bench Mark below?
  Sugarloaf Trig (TP5298) point is directly above a Survey Mark, identical to the one I listed in TP5618, hence my confusion.
  Does this mean I can log Sugarloaf as both a Trig and a Survey Mark?
  How exactly do you go about locating a Survey mark's name if you find one, as I did, by accident?

- cheers David

[caughtatwork]

I am not knowledgeable enough to tell the difference.
http://wiki.geocaching.com.au/wiki/Trigpoint

A benchmark/survey mark is a bronze disc which is also used by surveyors and are either points of known location (latitude/longitude) or height. A trig point will always be assosiated with a survey mark, however survey marks can be independant of a trig point.

Confused? So am I.

[Kerry]

I am not knowledgeable enough to tell the difference.
http://wiki.geocaching.com.au/wiki/Trigpoint

A benchmark/survey mark is a bronze disc which is also used by surveyors and are either points of known location (latitude/longitude) or height. A trig point will always be assosiated with a survey mark, however survey marks can be independant of a trig point.

Confused? So am I.

What's confusing? Or is the thinking there is no distinction between the Trig station (the marker/sighting bit) and the actual survey mark which generally coordinates/controls/references the marker bit

[caughtatwork]

The plate at the bottom is what confuses me.
Some plates used to (or still have) a trig station above them.
Some plates never had a trig station above them.
Based on the plate itself, how can you tell whether it's a survey mark and never had a trig station or whether it's a survey may that did have a trig station above it?

This appears to be a survey mark where there is a trig station.
http://geocaching.com.au/gallery/cache/tp1931

This, which looks different, is a survey mark where there is a trig station.
http://geocaching.com.au/gallery/cache/TP5298

This looks like the marker from TP5298 but has no trig station (as it's on a public street).
http://geocaching.com.au/gallery/cache/TP5618
http://geocaching.com.au/cache/tp5618

So I suppose the confusion (with me at least) is that survey marks may have had a trig station, but it's no longer there vs. survey marks still have a trig station vs. survey marks that never had a trig station. Does the type of disk tell you what they are?

[Apty]

My understanding of trig points is that it's got something sticking up! So the first 2 examples.

If it's just a brass plate on the ground or in a pit, then it's a survey mark and doesn't qualify as a TP.

However, if the TP has a brass plate you can claim the brass plate as a survey mark for the Locationless caches that are for finding Survey Marks. (As well, as the actual TP)

Clear now?

[Kerry]

caughtatwork,

I would class trig station (as such) as a secondary marker that was used basically in the days when instruments could read angles better than instruments could read distances over very long distances. So basically the "trig station" was a reference sighting point for angles usually positioned over a permanent survey mark, the brass plague etc fixed in the ground. Many of these sites, ground marks would also have recovery marks, normally three and some would have had ecce stations as the main station might have not been able to be occupied for quite a few reasons.

Trig stations saved a lot of work to fix temp reference sights as these types of stations are usually high on hill/mountains/structures etc with restricted or time consuming access.

Trig stations are in the minority when compared to the 1000's and 1000's of permanent type survey marks. The marker/disk type does not really define what was there. There was basically no specific design for trig stations but the prime purpose of the disc/topmark was 360 Deg visibility horizontally as well as a good vertical reference point.

Today with GPS trig stations are a thing of past era's

Your first two links have images of "trig stations" which are the structures/discs etc, the last two links are simply Permanent Survey Marks (PSM) and would never had a "trig station" (as such) but would most likely be coordinated horizontally and/or vertically (generally/maybe). BUT note that not all PSM's are coordinated as they could simply be used as a reference mark (PSM) for a cadastral boundary corner etc.

[caughtatwork]

So in simple terms (that make it clear for me anyway), a TrigPoint is a survey mark with a "structure" over it.
If the structure is still there, it's a TrigPoint.
If the structure is no longer there, then it's a survey marker?

[oz lurker]

And just to throw some more mud into the water, what if the coords are there (well, they would be wouldn't they - ROFL), there is some form of marker (ie cairn, manmade hole in the rock etc) but its NOT a brass plate or a metal frame thingy??

Two that I have found like this include http://geocaching.com.au/cache/tp4554 and http://geocaching.com.au/cache/tp3327.

Now, following the GCA ethos of 'cache the way you like' I'm claiming and keeping the FTF's for these - they were both up really big lumps of rock!!! But, they don't qualify as trigs according to the 'guidelines? explanations? whatevers..' in this thread.

But irrespective of that, they were both fantastic climbs, with brilliant views that I really doubt I would have clambered up there if it wasn't in search of that smilie - and are highly reccomended if you happen to be in the vicinity.