Trig points - a general discussion

[pjmpjm]

[There has also been discussion about what stops working if for some reason the GPS system becomes unusable, either due to solar flares knocking out the satellites or local interference - there was a case where a US Navy Ship in port was testing some gear and took out the local GPS receivers. This led to a shutdown of things like mobile networks and ATMs that rely on the exact timing received from GPS satellites. Does it also mean surveyors nowadays would be unable to work properly as they have lost the skills of doing it the old way?

I think this is an excellent point and also applies to a great many other modern technologies. A very basic example would be loss of electricity! Hard to imagine shops and banks and offices functioning in any useful way whatsoever.

Yes, I've read quite a few articles pointing out that a major solar flare could knock out a lot of our modern infrastructure. Many so-called 'primitive' countries would keep on keeping on quite nicely, but we in Australia would be approaching the source of a tributary without visible means of locomotion. Mrs. pjmpjm and I now have a water tank and wood stove up here in the Blue Mountains, just in case. But where would I get batteries for the GPSr? And if the orbiting GPSs packed up? It's too awful to contemplate . . .

[Tankengine]

Well – even if they still had the knowledge – they would have a tough time! What, with many trigs now long gone, and yet others very obscured… Check out this little beauty I found! (Bendora Trig!) http://geocaching.com.au/cache/tp5303 - I was 10m away, and I couldn't see it! - I'd love to see a surveyor sight that!

[Richary]

I found one at a cache in the Barrington Tops area a few years ago. Totally surrounded by trees much taller than it was, and it was the full disk unit. Unfortunately due to battling leeches I didn't grab a photo of it to claim a retrospective find.

Back to the main topic, if we agree Geoscience Australia is incomplete, perhaps we need to accept that anything listed as a trig by the various state departments is also fair game. Whether there is an easy way of getting that information I don't know. Personally while I prefer intact trigs, I have found some missing their black disk but the base is still intact. How far does one go in deciding when a trig is extinct?

To add to the discussion, at the top of a building in Crows Nest is a complete black disk arrangement sitting in the plant room. I can only assume it used to live on top of the building. I have a photo of it, so if it appears on someone's database as being a real trig I guess I can claim it

[Kerry]

A "Trigonometrical Station" (Trig Stn) by definition is a survey station that was used as part of a survey network to determine coordinates primarily by trigonometry from angular measurements, hence the typical sighting vanes and location on prominent features. A sighting mark with a clear background (sky) was ideal as opposed to say sighting from a prominent feature with no background contrast.

Measuring angles over long distances was much quicker than measuring distances (tens of miles) with the measuring equipment of the day. However any network still required a highly accurate baseline which would typically be measured along the best ground possible. Such baselines took years to measure and establish and not all stations in the network were on prominent features.

Not all infomation will be readily available to define if a survey mark was used in a trig network or not. The most obvious feature of a guaranteed trig station is 1) Beacon, second would be height (prominent feature), third might be infomation gleaned from the Survey Control Data Base station summaries. Note that anybody can purchase control station summaries/sketches (in Qld it's a few dollars over the counter) which can be done on a specific mark ID (if you have the number) or an area search based on multiple selective criteria.

[Tuena]

Just added nearmap to GSAK following the advice provided by Murf. No coverage in my area so selected a trig in Caringbah to test it & zoomed in. Pretty amazing. Pity it only covers a small fraction of the state.

Checked a trig behind Jamberoo which is in nearmaps coverage area. There are degrees of clarity. Fine detail in the metro area, fuzzy in rural areas. Amusing.

[Big Matt and Shell]

I'm familiar with three kinds of survey markers, all compiled somewhere in the overall NSW DOL database.

TS means 'Trig Station.'

PM means 'State Survey Permanent Marker.'

SS means 'State Survey Marker.'

Don't suppose you can narrow it down any from there...

EDIT: Don't worry, I found it here

[Tankengine]

OK, so there have been a number of ideas tossed around as to what does, and does not constitute a trig… But no definitive criteria… So maybe some criteria can be set?

Now, I’m by no means an authority on trigs (although I have found about 70, of which I have originally published around 20), so here are my thoughts… Maybe this list can be amended as required?

What should be considered a trig:
1. Trigs must be listed as a proper trig in a government website.
2. ADDITIONALLY – at GZ there must be either:
- a recognisable trig at that location, be it a quad beacon, rock pile, trig pole, steeple etc, or
- significant/recognisable remains of what is listed above. (ie bent poles, concrete platform showing where a quad beacon was once attached, rock pile without the marker pole, etc

Additionally:
What should NOT be considered a trig:
Even if listed as a proper trig on a government website (Those sites contain known errors – they even admit it), the following should NOT be accepted:
1. A lone bolt or unnamed stub,
2. A yellow (or other colour) survey pole (even if accompanied by a stub),

What I am in two minds about, as to whether it should be allowed:
- A bronze stub accompanied by a plate showing the name of the trig? (Any suggestions)

[mtbikeroz]

OK, .......


What I am in two minds about, as to whether it should be allowed:
- A bronze stub accompanied by a plate showing the name of the trig? (Any suggestions)

ie, like

[Tuena]

What should NOT be considered a trig:
Even if listed as a proper trig on a government website (Those sites contain known errors – they even admit it), the following should NOT be accepted:

2. A yellow (or other colour) survey pole (even if accompanied by a stub)

I can think of three trigs I found that if the latter point was accepted may not be considered trigs. Yellow, blue & red striped steel poles. These were listed as trigs from the original GeoScience download. Other trigs are just lumps of concrete with letters & numbers, some with plain steel poles surrounding them.

I've yet to see a pole with survey written on it in NSW so perhaps they are unique to the ACT.

Hard to argue against an authority which says xyz is a trig. The disclaimers I've seen relate to accuracy of the co-ords. Perhaps if someone is going to list one of these coloured survey poles as a trig they should say so in the description. Then we can decide whether to look for it or not.

Is Pialligo Trig a trig or a survey pole?

[Tankengine]

Well, I recon that Pialligo trig is a trig… Others may beg to differ. It is listed in the ACTPLA website as a trig of type MC, and it has a tall coloured pole, that can be accurately sited from a distance. – Now if the tall pole wasn’t there, and it was just the short yellow poles, I would say it wasn’t a trig. (As it can’t be accurately sighted). Ah well – nothing is ever as easy as it seems…

[Tuena]

Well, I recon that Pialligo trig is a trig… Now if the tall pole wasn’t there, and it was just the short yellow poles, I would say it wasn’t a trig. (As it can’t be accurately sighted).

I can show you dozens of trigs, in the classic style, that can't be accurately sighted.

[Kerry]

What I am in two minds about, as to whether it should be allowed:
- A bronze stub accompanied by a plate showing the name of the trig? (Any suggestions)

It makes little difference what the type of "marker" is and there appears a misconception that it has to be some official worded brass plague etc As long as the marker is of suitable material and in general trig type station markers will probably vary more than the typical run of the mill permanent survey marks

During the war the US & Aus surveyors also used spent ammunition cases in conc and these are still around today but being army may not be listed.

[Josh Hoogs]

Alot of trigs have appeared on the map around Warragamba Dam. Most of these are there from viewing of Google earth, but these are in Catchment area which is banned from public as far as I know. However, If you are able to spot them from the public viewing side of the dam, are you able to log as a find?? and if in catchment area, should they be achieved??

[rogerw3]

The Warragamba catchment area is a no go zone and closed to the general public. You can however ask the Water Board for special permission to access this area. I did this some years ago when doing a bush walk thru the area to walk up the Kowmung River to Kanangra Walls (several day walk). I had no problem getting permission to do this as long as you abide by their conditions, which were only common sense. The only restriction was that the area close to the reservoir could be crossed but you could not stay overnight.
In any case if you can see the Trig and get a photo without trespassing that is fine, otherwise you will need to ask for permission.

[GammaPiSigma]

I posted a "Needs Archiving" note on TP5712 - Trial Hill as it is within the 3km exclusion zone around Lake Burragorang. I have checked this TP's location against the Bimlow (8930-2S 3rd Edition) topo map and it is well within the Schedule 1 zone. The SCA guidelines can be found here: http://www.sca.nsw.gov.au/the-catchment ... cial-areas.

My understanding from research and discussions with NPWS staff is that just about every location within the Schedule 1 zones are strictly out of bounds. I do know of people who have obtained permission to enter the Schedule 1 areas but I don't like your chances of getting permission to enter these areas without a very valid reason.

Personally I think that any TP's that are located in the Schedule 1 zones should be archived. I would hate for any members of the geocaching community to end up in trouble and being fined for trespass. Also, all the work that has gone into developing a relationship between the caching community and NPWS doesn't need the sort of hassle that would result from geocachers being found within prohibited areas.

Just my thoughts on the matter.

Cheers,
Michael.