Are reference marks and underground marks obsolete?

[WhistlingWind]

I like finding the 1930's era triangulation stations

in my area, for some reason they seem 'special'.

 

A question regarding GPS and modern survey practices when setting a new horizontal stations:

 

Given GPS and WAAS, do modern surveyors still set RM's and underground marks like they used to, or do they just set a surface mark?

 

W. Wind

[Z15]

No, they do not set RM's or underground marks anymore. Azi marks are still being set but not from astromonical observations, e.g the North Star (Polaris) was the method usd to establish an Azi on triangulation surveys.

 

With GPS, its much easier to recreate the position or even establish a new position for any work.

 

[This message was edited by elcamino on March 30, 2003 at 09:18 AM.]

[+Kewaneh & Shark]

It's very astute of you to realize that the reference marks for a horizontal benchmark are probably not necessary any more given the technology that is now available to surveyors. Those reference marks were set in order to help locate the mark if it was covered (or hidden in some other way), or re-locate it if it had been disturbed or destroyed. With the more modern, survey-grade GPSr's, the benchmarks can be set to sub-centimeter accuracy, and that position can be found again using the same technology.

 

You topic question asks if "Are reference marks and underground marks obsolete?" Simply put, the answer is no. They are no more obsolete than the benchmarks they reference. As ElCamino said, they are no longer set, but the existing RMs can be, and still are necessary to find the benchmarks that have not been occupied using the survey-grade GPSr's. They can be especially helpful in locating benchmarks that have not been 'seen' in a while.

 

Keep on Caching!

- Kewaneh

[Z15]

Another reason for the RM's was to verify the station position.

 

Anytime you reset a station from the RM's or the underground mark, NGS will downgrade the position to 3rd order class.

[WhistlingWind]

Right, my topic would have been better phrased as "is the *practice* of setting RMs and underground marks obsolete?".

 

So do you guys still use the 'old ways' much at all to set horizontal marks?

 

My guess is that the old long-range triangulation techniques (long baselines, distant observations, precise measuring of angles, towers ,lights) are something that pretty soon only the old-timers will remember having used...(like older navigators remember sextant and chronometer, but love their GPS!).

 

W. Wind.

 

(ex-celestial navigator -- now GPS exclusively)

[survey tech]

WW

Your guess is correct. Technology has had a tremendous impact on the surveying profession. It is now far more cost effective to survey large areas using GPS than the traditional methods. In the future this will only accelerate, but for now, many if not most surveyors make little or no use of GPS, primarily due to the fact that they work mainly on small projects, where it is of little if any benefit, and thus is not considered worth the cost of the investment in survey-grade equipment. So for most local surveying companies, traditional methods are still the standard.

[Z15]

ALso it should be noted that a great many local surveyors rarely if ever use the triangulation stations or other horizontal control in thier everyday work. Many use the bench marks if avaialble and needed in thier projects. They don't need that data for property surveying or retracing section lines.

 

But for the most part, the small the outfit, the less they need or will use the NGS info.

 

Survey grade GPS equipment can set you back a good sum of money. While I worked for the DOT, we used Leice GPS System 500 Geodetic grade and RTK. 3 receivers and all the associated tools cost approx. $75,000 per crew with one base station and two rover RTK units.

 

Funny story on the local news one day last fall. Seems this surveyor for a big land company was doing some GPS work and had one of his receivers sitting on a 1/4 section corner and they were up to a mile aways setting more corners when someone up and stole his equipment. They even broadcast on the radio for anyone who may have seen someone take the equipment. The next morning a deputy sheriff stopped at the coounty highway department office and told the surveyor, you forgot your GPS equipment along side of county road x which is on my way home. That when he found out, it was not the county equipment he had but the stuff that was reported stolen the evening before. He must have felt like a fool.

[+Kewaneh & Shark]

One term that comes to mind in whether or not we use the 'old ways' is 'New Tools, Old Rules'. Technology has has advanced the surveying industry at a seemingly exponential rate in the past 10-20 years. Not only in speed, but efficency as well. When it comes to collecting, processing the data, and survey layout, the technology (the new tools) are a godsend, but the way that the surveying was originally done on a particular site (the old rules) must be understood as well. A piece of surveying equipment that can measure to the hundreth of a millimeter both horizontally and vertically won't be much use when you're searching for a point that was set one-hundred years ago with a surveyor's chain and angles turned to the nearest quarter of a degree.

 

The old-timers may be the only ones that actually remember using (and in some cases still use) the old equipment and techniques, the new-timers have to understand them as well. In this way, the 'old ways', are still in use. But you are correct in the fact that the actual practice of those techniques, especially on larger surveys, is not all that common (read: cost effective) anymore.

 

Keep on Caching!

- Kewaneh