Courthouse Disk "1892" Date Incorrect

[+Neweyess]

I'm not sure how to report this in the official form? I'm not sure if it's "Good" since it's there or "Poor" since the information in the NGS database is incorrect.

 

I was passing through Blairsville, GA when I saw an old courthouse. It turns out there is a benchmark on the foundation with the PID number: ED0700

 

Well, this is a bit strange. The benchmark has "1892" stamping and the NGS database also says this disk was "Monumented" in 1892". But this Union County Courthouse wasn't built until 1899?

 

Later, I checked with the Union County Historical Society and Steve Oakley, the director, confirmed that this courthouse was rebuilt in 1899 on a new foundation. Therefore, the disk could not have been monumented on this particular courthouse foundation in 1892.

 

Mr. Oakley also mentioned, "It appears to me that the original elevation was stamped as 1926 feet, then at some later time struck through and 1892.516 was added at the top, and 1892 just below the 1926 strikethrough."

 

Apparently, the 1892 elevation was confused as the date by the surveyor who made the original entry into the NGS database.

 

I also found that some other area Georgia disks in this number series were monumented in 1933.

 

Neweyess

[evenfall]

Interesting, But not too hard to sort out.

 

First and most important, the Datasheet has on it this all important line:

 

ED0700* NAVD 88 - 576.857 (meters) 1892.57 (feet) ADJUSTED This is the current elevation, and is what the surveyor is going to need to know. Since it is adjusted to NAVD 88, they will know it is current, or at least reasonably so.

 

Though the elevations seem confusing to the year, here is what the lowdown is on elevations as based on Vertical Datum:

 

If we work backwards from the latest info on the sheet, we can know that the NAVD Datum went into effect in 1991. That represents a variable Datum Shift from the NGVD 29 Datum, depending on where you happen to be checking elevations on the Geoidal reference Sphere (Gravity Model). This datum shift almost always will represent some sort of elevation change. NAVD 88 is currently using the Geoid 99 frame of reference for this station. The NGVD 29 Datum really didn't use a reference spheroid, and so really didn't take gravitational effects into consideration for it's calculations. It based elevations off the observation of a series of 26 tidal gauges, 21 in the US and 5 in Canada. Prior to the NGVD 29 which averaged all 26 references, there was likely a local reference or two that had been being used to establish elevations in the Area. Anyhow, the users of the BM will know to use the most recent data when dealing with this station as the old data is no longer considered up to date, UNLESS a local municipality is asking for them to us an older datum. This is sometimes the case. Either way, that data is on the sheet too.

 

So there are two approaches you can use here if you like. Your choice.

 

1. You can send in what you know to the datasheet entry form, from your find as a straight submission to this datasheet. That you noted the monumentation date confusion and noted the buildings build date. That the stamping "1892.516 feet is now a superseded value and that it be ignored, (though most users of BM's know not to use any value which has been stamped on them) And if you have it, Please add your GPSr waypoint: Lat/Lon dd.mm.ss NAD 83 data to your submission to tighten up the Horizontal scale to find info.

 

2. or, You can write Cheryl Malone at NGS cheryl.malone@noaa.gov and try to explain what you find odd about the date of monumentation in the Data sheet and if she would research to see if the USGS data for this USGS BM has a different date of Monumentation that the erroneous data on the NGS sheet, and if so, please make the necessary corrections. Then after she has done what she felt was appropriate, then submit your find to them based on the corrected datasheet as opposed to the erroneous one.

 

This is a USGS BM and not an NGS BM so the conventions for naming and stamping are different and sometimes open to interpretation. This could have also been a data entry error from when they added this to the electronic database. In any case, the NGS has information on this station in various archives that may aid them in sorting all this out.

 

I hope I didn't confuse you further and gave you a little background as to why other stamped BM's may no longer seem correct as well.

 

Good Luck!

 

Rob

[Z15]

I got a pretty good idea of what maygoing on here. It was never monumented in 1892 as you have deduced, someone confused the stamped elevation as being the date set because it is stamped 2x, possibly by the field crew or the person who entered the data into the computer in the 1980's.

 

Some of these old marks were stamped with the elevation to the closest foot by the level party doing the work and later stamped again with an adjusted elevation. I recall seeing some instructions to level parties to halt stamping elevations on the survey disks. 1892 is not the date, if it was anything but the elevation then I would say it was but thats too much of a coincidence + the fact the building was not even there is proof to me that its not a date. I can't recall the exact year but I think 1892 may be before the use of survey disks but I will have to check into that.

 

I bet the date set is unknown, lots of these old USGS marks have vague records as to when they were established. I guess back then they never figured anyone would care about it today and they never planned ahead.

 

 

Cheryl will likely change the date monumented to UKNOWN

 

 

Figure 16. Charles Doolittle Walcott, Director of the U.S. Geological Survey, 1894-1907.

 

Figure 17. Bench marks, showing elevations above sea level, greatly enhanced the value of topographic maps, 1896.

 

The development of the topographic work followed a similar pattern. Before Walcott became Director, the work of the Topographic Branch of the Survey had been criticized by many who considered the extensive program inappropriate for a geological survey and more properly part of another organization, but at the beginning of his directorate Walcott simply announced that topographic map quality would be improved. Within a few months, the topographic corps was placed under Civil Service, thus eliminating some of the difficulties of the Powell era when many with inadequate or no training, including congressional relatives, had been employed. A practical demonstration was made of the advantages of combining topographic surveys and the subdivisional surveys of the General Land Office in Indian Territory. The value of topographic maps for practical purposes was greatly increased by the placement of permanent bench marks showing the exact location and elevation of fixed points.

 

 

History of the USGS

Edited March 13, 2005 by elcamino

[evenfall]

In the earliest monumentations I could find in Washington State, still extant, the stations began life as drill holes (Triangulation 1854). The earliest I recall any of the drill holes updated to brass discs out here was 1902 revisits to the drill holes, 1880 era revisits were finds of drill holes and sometimes the drill hole was found to have a stick in it or it was cleaned and repacked with sulfur to aid in finding it again at a future date.

 

As to leveling, Most of what is out here on the West Coast would have come after the Brass disc, However Bolts and Rivets or some such item could have been used to signify a leveled location prior to the discs themselves in the East, Prior to disc Monuments. It is hard to say when the USGS was doing it's leveling and or when they did that Court House, But writing the USGS about it as it says on every disc may unearth an answer. Dave D may also have a line on some of the info, and maybe he will see this and look into it if he has time.

 

To Casey or DaveD, Do you guys have any internal documentation as to when the USCGS began using brass disc style station markers? My best guess is 1890's or early 1900's from what I have come across, But I have never read anything in the NGS History, so far, as to when exactly the practice was undertaken. Any thoughts?

 

Just to help out with when Leveling became Geodetically important and how the beginning was carried out, Here is a quote from:

 

http://www.history.noaa.gov/stories_tales/geodetic5.html

 

Geodetic Leveling, Datums, and Instruments

 

Geodetic leveling has always played second fiddle to horizontal surveys. Perhaps this is so because leveling is perceived as a simple procedure, although it most certainly is not. Some form of leveling, mostly trigonometric in nature was always observed in order to provide elevations needed to reduce base lines and angle observations to sea level. As a matter of fact, the observations were often carried out as a separate event using specially constructed vertical circle only instruments.

 

As work on the Transcontinental arc progressed westward it was recognized that vertical angle elevations would not be of sufficient accuracy for the purpose. Accordingly a line of precise levels following the route of the triangulation was begun in 1878 at the Chesapeake Bay and reached San Francisco in 1907.

 

In 1898, an adjustment was made of the first 25 circuits and a second in 1903 to include the large amount of new data observed in the interim. Partial adjustments were carried out in 1907 and 1912 to include the ever increasing work. In 1929 a general adjustment was made which included 45,000 miles of U.S. first-order leveling and 20,000 miles of similar accuracy Canadian surveys, with sea level planes at 26 tidal stations held fixed. The Canadians had recently published the results of their observations and didn't accept the combined adjustment values. Difference of elevations at common bench marks didn't exceed 0.5 ft. The U.S. data also includes precise leveling observed by the Corps of Engineers, U.S. Geological Survey and other organizations.

 

By 1940, about 260,000 miles of first- and second-order leveling had been observed. The elevation datum was known as the Sea Level Datum of 1929 (SLD29) until 1973 when the name was changed to the National Geodetic Vertical Datum of 1929 (NGVD29).

 

Prior to 1899, geodetic leveling in the U.S. was observed using wye levels and target rods. Long telescopes were common to such instruments and critics claimed Americans bought their levels by the yard. In 1899, the Fischer level designed by Ernst G. Fischer of the instrument division, a dumpy type and speaking rods replaced the earlier equipment and were used for almost 70 years with only slight modifications. Invar strips were added to the rods in 1916.

 

Rob

[+Neweyess]

 

 

Cheryl will likely change the date monumented to UKNOWN

How significant is the PID sequence for date reconstruction?

 

The mark with the questionable date is ED0700. Both ED0699 and ED0701 (as well as many other near-numbered ones) all have the monumented date of 1933.

 

Gary

[evenfall]

Neweyess,

 

The PID system was developed well after the 1930's.

 

Basically the PID system is in theory no different than you knowing that you keep the socks you wear in the top dresser drawer on the left side. You know that if you look there, what you expect to find will be there. The PID is a drawer or a folder that contains the Data for a station named X... The near by stations were well, nearby, so they received a sequential PID...

 

But Basically, the PID is just a computer file name for data ascribed to a particular station, that is it. The Data in the file will have what there is to know about the station, and there may be data which NGS has that is not important to the datasheet itself, but is on file about any particular station...

 

Hope that helps...

 

Rob

Edited March 14, 2005 by evenfall

[+Neweyess]

Basically the PID system is in theory no different than you knowing that you keep the socks you wear in the top dresser drawer on the left side. 

Rob,

 

Thanks for your reply.

 

I understand that the PID is basically an ID and a record locater. What I was trying to get at is whether or not we can use the sequence to help determine the date? With ED0700 being sequentially in the middle of ED0699 and ED0701 (as well as others to either side) all having the monumented date of 1933, it would seem to indicate more than a strong possibility that ED0700 was also monumented in 1933.

 

Perhaps there is a reason that the sequence does not help determine the date (or at least exceptions) and that's what I was asking?

 

Gary

[evenfall]

Hi Gary,

 

That idea you have would be very cool if only it were true...

 

See, all the old marks were hand written and typewritten Data. elcamino, aka Z15 has some photos of the old datasheets, and maybe he will post one here as an example.

 

Anyhow, The NGS had Files and Files of these datasheets and so the people at NGS sat down and hand entered the data into computers... there was no OCR software involved. Talk about looking up at the bottom of a big mountain with a very long hike to go.

 

Now if there was a rhyme or reason as to how the stations were kept in the files prior to being given a PID, I have no Idea. I can tell you from my experience with the Numerical order of the PID system in the N.W Washington State area, that if you were to plot this on a map, PID for sequential PID, a lot of it might appear pretty random. Sometimes it will chase a Level line but triangulation will look like a shotgun pattern and the two major station types will intermix as well. I could never really count on sequential anything although I did observe it from time to time.

 

So, If there seems to be a rhyme and reason, it only seems to at some times, and this is not a searchable thing, it is just happenstance. If we want related stations, we can look up the level line itself, or on Triangulation Stations with a Box Score section, we can find related data there but that is about all I can think of which will interrelate things beyond the luck of how they had been kept in the files back when.

 

There was a lot of CGS station monumentation performed in the 30's as part of the New Deal, and that is why we see a very large body of work from that era.

 

I suppose you could search for date specific stations and radial or rectangular searches for nearby stuff, but I fear you may have to read each one to make sense of it all if there is a link at all.

 

In the case of ED0700, I am not sure what can be said about this. We are not sure about part of this as we are sure an error has seemingly been made. Further we have a case where either the NGS has adopted a USGS station for it's use, or the USGS submitted to the NGS for inclusion at some point in time. This could have happened during the 1930's but if it did, it will not become part of any hard and fast rule we can all use to think of PID sequences in a certain way, It will just be something that happened that way. Pure Happenstance. In any case, I am sure that you have found some erroneous information on the datasheet for this Station.

 

My call on this one would be to email and ask Cheryl at NGS if there is more to this station apparently meets the eye. My take on it is that she may be able to sort out some things we cannot see. Other Data which is likely there but not needed for the datasheet may tell more of the tale. It may be interesting, since this was first a USGS Station to write them and see what their Data has to say, and Perhaps NGS has this information in archive as well. Sometimes they will.

 

So you see, the sequence does not necessarily help us with dates, or any other similar data as the PID system is a part of the Computer Age and the Data ascribed to the stations does not always follow a particular hierarchy of any kind which can be logically followed. Beyond this, the best tool seems to be our own brain and our familiarity with the datasheets for the Stations in our local area. Local Knowledge makes you one of the local experts.

 

Good Luck Gary!

 

Rob

Edited March 21, 2005 by evenfall

[Z15]

[+ddnutzy]

In the earliest monumentations I could find in Washington State, still extant, the stations began life as drill holes (Triangulation 1854).  The earliest I recall any of the drill holes updated to brass discs out here was 1902 revisits to the drill holes,  1880 era revisits were finds of drill holes and sometimes the drill hole was found to have a stick in it or it was cleaned and repacked with sulfur to aid in finding it again at a future date. 

 

As to leveling, Most of what is out here on the West Coast would have come after the Brass disc, However Bolts and Rivets or some such item could have been used to signify a leveled location prior to the discs themselves in the East, Prior to disc Monuments.  It is hard to say when the USGS was doing it's leveling  and or when they did that Court House, But writing the USGS about it as it says on every disc may unearth an answer.  Dave D may also have a line on some of the info, and maybe he will see this and look into it if he has time.

 

To Casey or DaveD, Do you guys have any internal documentation as to when the USCGS began using brass disc style station markers?  My best guess is 1890's or early 1900's from what I have come across, But I have never read anything in the NGS History, so far, as to when exactly the practice was undertaken.  Any thoughts? 

 

Just to help out with when Leveling became Geodetically important and how the beginning was carried out, Here is a quote from:

 

http://www.history.noaa.gov/stories_tales/geodetic5.html

 

Geodetic Leveling, Datums, and Instruments

 

Geodetic leveling has always played second fiddle to horizontal surveys. Perhaps this is so because leveling is perceived as a simple procedure, although it most certainly is not. Some form of leveling, mostly trigonometric in nature was always observed in order to provide elevations needed to reduce base lines and angle observations to sea level. As a matter of fact, the observations were often carried out as a separate event using specially constructed vertical circle only instruments.

 

As work on the Transcontinental arc progressed westward it was recognized that vertical angle elevations would not be of sufficient accuracy for the purpose. Accordingly a line of precise levels following the route of the triangulation was begun in 1878 at the Chesapeake Bay and reached San Francisco in 1907.

 

In 1898, an adjustment was made of the first 25 circuits and a second in 1903 to include the large amount of new data observed in the interim. Partial adjustments were carried out in 1907 and 1912 to include the ever increasing work. In 1929 a general adjustment was made which included 45,000 miles of U.S. first-order leveling and 20,000 miles of similar accuracy Canadian surveys, with sea level planes at 26 tidal stations held fixed. The Canadians had recently published the results of their observations and didn't accept the combined adjustment values. Difference of elevations at common bench marks didn't exceed 0.5 ft. The U.S. data also includes precise leveling observed by the Corps of Engineers, U.S. Geological Survey and other organizations.

 

By 1940, about 260,000 miles of first- and second-order leveling had been observed. The elevation datum was known as the Sea Level Datum of 1929 (SLD29) until 1973 when the name was changed to the National Geodetic Vertical Datum of 1929 (NGVD29).

 

Prior to 1899, geodetic leveling in the U.S. was observed using wye levels and target rods. Long telescopes were common to such instruments and critics claimed Americans bought their levels by the yard. In 1899, the Fischer level designed by Ernst G. Fischer of the instrument division, a dumpy type and speaking rods replaced the earlier equipment and were used for almost 70 years with only slight modifications. Invar strips were added to the rods in 1916.

 

Rob

Rob,

MY3686 (Waterbug) is a NGS Benchmark disk documented in 1887. This is the oldest disk that I have found so far.

 

Dave

Edited April 3, 2005 by ddnutzy

[evenfall]

Hi Dave,

 

Unfortunately the monumenting narrative was omitted from the datasheet. It is an old station to be sure, but beings that this is a drill hole in a rock that the Monumentation is in, and based on the History of the Industrial Age, the original Monumentation was not the disc. The Steel Industry was young, this era was very pre internal combustion and electrical power, so I imagine the disc we see in your recovery picture was placed at the time of the 1939 recovery. I do wonder how it was defined prior to receiving the disc. In any case it is an old survey.

 

There is one error in the datasheet though. The Narrative calls this a Second order mark, but it is listed as a Third. It is possible this was not an error really, there was a time when the CGS or NGS redefined the methodology for defining Order and that re definition may have been a factor in causing this station to be downgraded to third order.

 

Interesting.

 

Thanks!

 

Rob