How important are they?

[+GeoGeeBee]

I was going to reply to this statement, made in another thread:

 

Benchmarks are important to society. . .

 

But I think this question deserves its own thread.

 

I really enjoy hunting benchmarks. The history of them fascinates me. But are they really useful? With all of the satellites and electronics, how much do surveyors use these?

 

I enjoy hiking five miles down an abandoned railroad right-of-way to find a benchmark that hasn't been logged since 1934. But how useful is it for anyone to know that it's still there?

[Z15]

Working for 30 yrs with a state DOT I know we used them for elevation (vertical) control on all our survey projects and thus the road/bridge construction plans are based on them. 99% of the surveys we did were based on NGS datum.

 

Any work involving bridges, culverts, wetland mitigation had to he based on NGS vertical datum as required by permit applications to state and federal agencies.

Edited October 6, 2009 by Z15

[+MuckSavage]

I too am a Land Surveyor. I use them a few times per week, so yes, they are important for mine & the reasons stated above.

[+Renegade Knight]

... But are they really useful? ...

 

Even if they are fully replaced by some kind of electronic equivilent you would still need them to calibrate your equipment.

[+t8r]

The world is changing shape. BMs and tri stations are both useful to keep track of these changes. (geodetic survey).

A survey of a piece of land might have been done using a particular BM as a reference, after many years that BM may be the only reference still findable.

It's a total hoot to find one that others (ngs) have given up on.

Then there is the thrill of going after one or a set of tri stations who's paperwork got mixed up from the getgo.

I have been looking for NV1190, NV1188 for nearly 2 years now. The physical 'to reach' is over 30 miles from the coordinates given and the geography has changed a lot in the area described.

[+Klemmer]

I'm not a surveyor, but am quite familiar with the GPS satellite constellation and related military & space issues. I do not think anyone would advocate putting all our eggs in one basket (GPS). There are many sorts of things that can go wrong with GPS, for potentially years at a time (political, man-made & natural). The military is keeping back-up systems available (INS, TACAN, NDB, others). I believe that the FAA will also keep backups also (anyone hear any talk of taking down the US VORTAC system? - I haven't). No reason NGS shouldn't keep a backup as well. Survey Markers (of all sorts) are the backup.

 

BTW: Keep those street signs also!

[Bill93]

T8r, I went back and read the prior thread on your mystery marks, and see little to add. I ran the coordinates through INVERSE and it gives about 1.9 km between them at precisely the azimuths listed.

 

My take is that there were two pairs of stations that somehow had their information intermixed. If the military was involved, some of the data may have been classified at the time, and maybe nobody at NGS updated anything with the data when/if it was declassified. There are problems with the to-reach such as one saying SE and the other SW of Bruneau, but somewhere out there near Jack Creek there were a pair of disks in concrete stamped Able and Baker, and they do not have published PIDs.

 

I'd take Dave's suggestion to post recoveries saying "Found pipe and washer stamped xxxx within a few feet of listed coordinates. Coordinates 25 miles from to-reach information which may apply to a disk stamped ABLE. No evidence of disk in concrete found in vicinity of coordinates."

[AZcachemeister]

I was going to reply to this statement, made in another thread:

 

Benchmarks are important to society. . .

 

But I think this question deserves its own thread.

 

I really enjoy hunting benchmarks. The history of them fascinates me. But are they really useful? With all of the satellites and electronics, how much do surveyors use these?

 

I enjoy hiking five miles down an abandoned railroad right-of-way to find a benchmark that hasn't been logged since 1934. But how useful is it for anyone to know that it's still there?

 

Their value to 'society' might be questionable, but their value to surveying is unquestionable.

 

Certainly a surveyor could go out and collect four hours of data to run through OPUS and get an accurate location and elevation for a particular spot.

 

But, (and as a non-professional, I'm guessing here) they could probably shoot a bearing and angle from a existent benchmark, and get more accurate results in half the time. (especially for elevation).

 

EDITED for speeling.

Edited October 7, 2009 by AZcachemeister

[Bill93]

For at least the next 10 years, elevation benchmarks will provide more accurate elevations than can be obtained by GPS. Although GPS can get a height above the ellipsiod, that requires knowledge of the geoid (determined by the local strength of gravity) to convert into "orthometric height" which is what is obtained by optical leveling and is important for construction/drainage work. Until NGS collects a lot more gravity data, they can't make the conversion accurately enough for some purposes.

[Wintertime]

I've seen a bunch of benchmarks in Yosemite that had been cleaned off and flagged (pink tape on a nearby stake or an overhanging branch), obviously by NPS or contract personnel. So the pros obviously still find them helpful.

 

Patty

[+Geoextreme87]

They also have value for geologist (and I'm sure other sciences) too. If you are trying to map rock units with an altimeter you need a "base station" of known elevation to set your equipment and correct for drift. Since Benchmarks give you this info plus are on USGS Topo Maps they are a good candidate. Though you can do this with a fancy GPS (accuracy +/- 1 foot) the ones I was using required 5 minutes of uniterrupted signal to gather one waypoint and if you lost signal for even a few seconds you had to start over. In mountainous terrain, overcast skies, and thick woods the GPS proved difficult and yet we were still able to accurately determine our elevation thanks to that benchmark.

 

So in short yes they are still useful for society as surveying and science provide some of the structure needed for society to function.

 

Who would have thought a little bronze disk could be so useful?

Edited October 7, 2009 by Geoextreme87

[+Renegade Knight]

...Their value to 'society' might be questionable, but their value to surveying is unquestionable....

 

That's a fair distinction. Most all of my work I could do using an assumed datum and some temporary marks because I only need to build my project relative to it's immediate surroundings.

 

However my plans have information that is useful for other purposes. Property lines, elevations, locations of new features. When you want to put together a larger puzzle out of the pieces, if the pieces use the same datum derived from benchmarks it's a lot easier to tie it all together. The big picture is where most of the value to society comes from even though on any one project I could assume a datume and do just fine. Planning utility proejcts (you do like water coming out of your fauctet pipes and flush toilets?) cut across many smaller projects and developments. It helps a lot if each development used the same datum and benchmark system.

 

That said, some things require global benchmarks and a universal datum. Flood plain work for example. If I certify that your house is out of the flood plain, I better be referencing the right mark. I don't have the luxery of assuming anything.

[+m&h]

In Susanville, California, up on a bluff called Inspiration Point, there is a triangulation station, LT0527 SUSANVILLE, which appears not to have had much recent use. One of the marks tied in to it, though, is LT0119 N 843, an elevation mark which has been logged professionally on NGS ten times since 1991.

[+jwahl]

Some perception I have seen mentioned here I would like to comment on. That is that surveyors who use either horizontal or vertical control monuments log them to NGS.

 

That is not my experience. I would bet that 95% of surveyors do not or have not logged a report to NGS even though they are using marks.

 

This was particularly true before we had internet forms, so before 5 years ago?.

 

I think I might log a station if I found it destroyed or damaged so that it would not be useable and reporting that would save someone else time, but most of the time that effort is not made sorry to say.

 

- jlw

[+GeoGeeBee]

Some perception I have seen mentioned here I would like to comment on. That is that surveyors who use either horizontal or vertical control monuments log them to NGS.

 

I know I recently logged one that's a couple of miles from my house, and hadn't been reported since 1992. But it had fresh paint markers on the road and in a circle around the mark, so I know at least one surveyor has used it recently.

 

FY1895

[+GEO*Trailblazer 1]

snip

 

That is not my experience. I would bet that 95% of surveyors do not or have not logged a report to NGS even though they are using marks.

 

This was particularly true before we had internet forms, so before 5 years ago?.

 

I think I might log a station if I found it destroyed or damaged so that it would not be useable and reporting that would save someone else time, but most of the time that effort is not made sorry to say.

 

- jlw

 

In my opinion Professionals are the one's that SHOULD be logging these.

It is not that hard to fill out a form whether by internet or snail mail.

I would want to make sure everything on my Survey is up to date and I am getting paid for this service.

 

The pattern has not changed much in 5 years.

But there has been a big change in the past say 2 years.

I know that some if not most in this area have NOT been used nor updated by local pro's until after I started doing it.

 

The amount of build up on the marks is from them not being dug out and I have dug 90% of them out to recover.

 

I have tried to report it all as I can for volunteerism but after a while you can only afford so much volunteer time when you have little to work with.

 

I am proud that our Survey Chapter has given me high marks in our meetings lately as they state that they have used and know who CB is now and appreciate the updated marks they have to use...If they see CB on the NGS Data sheet they know it is there and able to be used.

 

We just did a level loop not to long ago for our GEOCAC Mark using a nearby benchmark but was found to be a little off so we went to the next closest to check our work and found the error.

 

So even us civilians can be said to have used them along with the pro's.

[+ezfool]

Benchmarks to surveyors are very important. In the city of Chicago there are marks that have been set by the city and it is on their local datum, which is about 600+ above sea level. Any condominium or building project which we are involved in, must be tied to these monuments.

 

when we work in the suburbs we tie into NGS monuments unless the village engineer requests something different, (local benchmarks) which have previously been tied into NGS in most cases.

 

when we doing anything for FEMA (flood plain or elevation certificates) we always tie into NGS monuments which in some cases can be a long level circuit.

 

As far as logging NGS monuments, we report if the are missing or destroyed, or have not been reported in good condition in some time. However, if it has been reported as good in the past few years and the description is still adequate we do not report. I know we should, but the bosses thought is not to fill the data sheet with lots of "found as described in good condition".

 

As a habit i hang or replace flagging tape in the area and spray paint near the mark to help keep in visible. in the city they are typically in small metal boxes with the lid at ground level. I try to clean them out and make sure the lid is in good order, which can be dangerous as the wells are a haven for needles and broken glass.

 

so to get to the heart of the question, are they valuable to society. YES, they are reference points that help things get built or located. Even with improving GPS technology i do not think they will ever stop being used because they are such an important check on the accuracy of our work