Sign in to follow this  
Followers 8
NGS Surveyor

U.S. Coast & Geodetic Survey Disks

31 posts in this topic

DISKS IN THE VICINITY OF A U.S. COAST & GEODETIC SURVEY TRIANGULATION STATION

 

Recently there have been several comments and questions about the different disks in the immediate vicinity of a U.S. Coast & Geodetic Survey (USC&GS) Triangulation Station. Standard procedure for the USC&GS (and after the name change in 1970, the National Geodetic Survey) was to set four disks at ground surface level, a TRIANGULATION STATION disk (where the survey observations were made), two REFERENCE MARK disks, and one AZIMUTH MARK disk. Underground marks may also have been set, see details below. The following

paragraphs are from a paper I wrote some time ago explaining some of the different USC&GS survey disks.

 

TRIANGULATION STATION - A Triangulation Station is a survey point established during a survey utilizing the triangulation surveying method. Triangulation consists of observing the angles at the vertices of adjacent triangles, measuring the lengths of some sides, and computing the lengths of the remaining sides. The goal of this procedure is to determine the horizontal positions (latitude and longitude) of the vertices of each triangle (the points marked by TRIANGULATION STATION disks). The triangulation method thus produces accurate horizontal positions but only approximate elevations. Later, if a leveling survey crew was nearby, they may have leveled to one or more of the disks providing more accurate elevations.

 

The standard for many years was to set four disks at ground surface level in the vicinity of a Triangulation Station. However, there may be 6 or more survey disks in the vicinity, counting underground mark(s), additional reference mark(s), and mark(s) of other organizations. Note, other agencies may have used the same station name so care must be taken in identifying the correct agency’s survey disk. The main station, marked with a Triangulation Station disk, contains the factory stamping “TRIANGULATION STATION” with an equilateral triangle in the center. In addition, an underground mark may have been set about four feet beneath the surface. First the lower mark was set in a small mass on concrete, then a layer of dirt was added to isolate the lower mark, then the concrete monument was added, and then the surface mark was set directly over the underground mark. The underground marks were set to preserve the surface mark’s position if the surface mark was damaged or destroyed. Both disks contained the same factory stamping (“TRIANGULATION STATION”) and contain the exact same stamped designation (name) and date. Triangulation Stations were normally named for an area feature or for the property owner. Just prior to setting, the disk would be stamped by the original surveyor, for example, “JONES 1936”. In the NGS database, the name would be “JONES” and the year set 1936. The disk was usually set so that the stamping could be read by an observer facing north. The surface disk would be set in a concrete monument buried in the ground, or set in a drill-hole in a large structure or bedrock. The concrete monument is normally about flush with the ground’s surface, 12 inches in diameter, and 48 inches or more deep, with the bottom larger in diameter to help resist frost heave. The USC&GS TRIANGULATION STATION type of disks were used from about 1900 to about 1970 (although there were several different versions). After about 1970, National Geodetic Survey HORIZONTAL CONTROL MARK disks were used.

 

REFERENCE MARKS - Reference Marks (RM) were set to assist in locating the Triangulation Station and also to help determine if the Triangulation Station was undisturbed in its original position. The measured directions and distances to them could also be used to reset a station mark if required. Reference Marks were factory stamped with “REFERENCE MARK” and with an arrow used to point in the direction to the Triangulation station. The original surveyor stamped the RM with the name of the Triangulation Station plus the number of the RM, just prior to setting. For example, the first RM for station JONES would be stamped “JONES NO. 1 1936”. The surveyor measured the direction and distance from the triangulation station to the Reference Mark (RM) and recorded the information as part of the station’s description. Later, if a surveyor attempting to find a Triangulation Station stumbled upon a RM first, the arrow and the published distance and direction between the RM and station would be valuable aids in the station recovery. To check the position of the Triangulation Station, the new surveyor could measure the angles and distances to the Reference Marks and compare them to the original values. USC&GS specified a Reference Mark as early as 1913. By the 1920’s, two Reference Marks per Triangulation Station were specified. Reference Marks were usually set within 30 meters (one tape length) of the station. Reference marks were numbered clockwise from north and set about 90 degrees apart. If a RM was destroyed, a new Reference Mark would be set using the next consecutive number. The disks would be set in a concrete monument buried in the ground, or set in a drill-hole in a large structure or bedrock. This type of disk was used from about 1913 to about 1970. Although the distance and direction provided enough information to compute the positions of the RMs, it was not standard procedure to compute them. After about 1970, National Geodetic Survey REFERENCE MARK disks were used.

 

AZIMUTH MARKS – Beginning in 1927, a third Reference Mark, or long RM, was set about ¼ mile away from a station. They provided a starting azimuth (direction) for local surveys and for determining magnetic declination (difference between true north and magnetic north). Standard Azimuth Mark disks replaced azimuth reference marks about 1935. Also in 1935 the precision of the directions to Azimuth Marks was increased by changing the number of repetitions of the angle measurements from two to four. Azimuth Marks visible from the ground at the main triangulation station had been frequently requested by local surveyors and engineers. Azimuth Marks were factory stamped with “AZIMUTH MARK” and with an arrow. The original surveyor stamped the Triangulation Station’s name and date on the Azimuth Mark disk, just prior to setting. Since this is the exact same stamping as on the Triangulation Station disk, persons recovering the mark must check the factory stamping of “AZIMUTH MARK” (with arrow) versus “TRIANGULATION STATION” (with triangle) to determine which is which. When set, the surveyor rotated the Azimuth Mark disk until its arrow pointed directly toward the Triangulation Station disk. The surveyor then measured the direction, and in later years distance, to the Azimuth Mark (from the Triangulation Station) and recorded the information. Measuring the distance to the Azimuth Mark began in the mid 1970’s when electronic distance measuring equipment came into common usage, and underground marks were set at many of these. Azimuth Marks were usually set between ¼ mile and 2 miles from the Triangulation Station, at a location that was visible from tripod height at the Triangulation Station, and generally in or near a fence line along a road. The Azimuth Mark was included in the “To Reach” portion of the station’s description. The distance to most Azimuth Marks was measured with an odometer, so most don’t have adjusted positions and many are a challenge to recover. The disk would be set in a concrete monument buried in the ground, or set in a drill-hole in a large structure or bedrock. This type of disk was used from about 1935 to about 1970. After about 1970, National Geodetic Survey AZIMUTH MARK disks were used.

0

Share this post


Link to post

Good info and nice reading, even for those of use that have been finding survey marks for a while. Thank you very much.

 

May I suggest that this topic be linked from, or added to our sticky "Me First!" topic at the top of the forum. I think it will be very valuable to new comers to our hobby. Could you do that, Oh great and mysterious UNK1?

Edited by Klemmer & TeddyBearMama
0

Share this post


Link to post

hello benchmarkers,

i had no idea that any of this existed until i began a project with two of my art students to identify the unknown infrastructure objects that appear up and down the length of 14th street in manhattan. plenty of mystery abounds. our research about one object led us here. we have found a geodetic marker -- a metal (brass?) plate, with a triangle and a center dot, and the number 143. i havent seen images of markers without any other identifying marks, and we cant figure out who is responsible for placing this. an email from the noaa says it isnt theirs. any suggestion about how to determine ownership?

thank you in advance! and happy hunting... this is all fascinating.

-margot

0

Share this post


Link to post

hello benchmarkers,

i had no idea that any of this existed until i began a project with two of my art students to identify the unknown infrastructure objects that appear up and down the length of 14th street in manhattan. plenty of mystery abounds. our research about one object led us here. we have found a geodetic marker -- a metal (brass?) plate, with a triangle and a center dot, and the number 143. i havent seen images of markers without any other identifying marks, and we cant figure out who is responsible for placing this. an email from the noaa says it isnt theirs. any suggestion about how to determine ownership?

thank you in advance! and happy hunting... this is all fascinating.

-margot

 

Welcome to Benchmark Hunting Margot,

 

If you would be so kind as to post a new thread in the Forum below with all of the info you have about this mark, someone will try their best to help. A picture would definitely help, coordinates, etc.

 

Shirley~

0

Share this post


Link to post

Very informative!

Being a Surveyor myself and nostalgic, I love recovering old Geodetic Monuments!

0

Share this post


Link to post

DISKS IN THE VICINITY OF A U.S. COAST & GEODETIC SURVEY TRIANGULATION STATION

 

Recently there have been several comments and questions about the different disks in the immediate vicinity of a U.S. Coast & Geodetic Survey (USC&GS) Triangulation Station. Standard procedure for the USC&GS (and after the name change in 1970, the National Geodetic Survey) was to set four disks at ground surface level, a TRIANGULATION STATION disk (where the survey observations were made), two REFERENCE MARK disks, and one AZIMUTH MARK disk. Underground marks may also have been set, see details below. The following

paragraphs are from a paper I wrote some time ago explaining some of the different USC&GS survey disks.

 

TRIANGULATION STATION - A Triangulation Station is a survey point established during a survey utilizing the triangulation surveying method. Triangulation consists of observing the angles at the vertices of adjacent triangles, measuring the lengths of some sides, and computing the lengths of the remaining sides. The goal of this procedure is to determine the horizontal positions (latitude and longitude) of the vertices of each triangle (the points marked by TRIANGULATION STATION disks). The triangulation method thus produces accurate horizontal positions but only approximate elevations. Later, if a leveling survey crew was nearby, they may have leveled to one or more of the disks providing more accurate elevations.

 

The standard for many years was to set four disks at ground surface level in the vicinity of a Triangulation Station. However, there may be 6 or more survey disks in the vicinity, counting underground mark(s), additional reference mark(s), and mark(s) of other organizations. Note, other agencies may have used the same station name so care must be taken in identifying the correct agency’s survey disk. The main station, marked with a Triangulation Station disk, contains the factory stamping “TRIANGULATION STATION” with an equilateral triangle in the center. In addition, an underground mark may have been set about four feet beneath the surface. First the lower mark was set in a small mass on concrete, then a layer of dirt was added to isolate the lower mark, then the concrete monument was added, and then the surface mark was set directly over the underground mark. The underground marks were set to preserve the surface mark’s position if the surface mark was damaged or destroyed. Both disks contained the same factory stamping (“TRIANGULATION STATION”) and contain the exact same stamped designation (name) and date. Triangulation Stations were normally named for an area feature or for the property owner. Just prior to setting, the disk would be stamped by the original surveyor, for example, “JONES 1936”. In the NGS database, the name would be “JONES” and the year set 1936. The disk was usually set so that the stamping could be read by an observer facing north. The surface disk would be set in a concrete monument buried in the ground, or set in a drill-hole in a large structure or bedrock. The concrete monument is normally about flush with the ground’s surface, 12 inches in diameter, and 48 inches or more deep, with the bottom larger in diameter to help resist frost heave. The USC&GS TRIANGULATION STATION type of disks were used from about 1900 to about 1970 (although there were several different versions). After about 1970, National Geodetic Survey HORIZONTAL CONTROL MARK disks were used.

 

REFERENCE MARKS - Reference Marks (RM) were set to assist in locating the Triangulation Station and also to help determine if the Triangulation Station was undisturbed in its original position. The measured directions and distances to them could also be used to reset a station mark if required. Reference Marks were factory stamped with “REFERENCE MARK” and with an arrow used to point in the direction to the Triangulation station. The original surveyor stamped the RM with the name of the Triangulation Station plus the number of the RM, just prior to setting. For example, the first RM for station JONES would be stamped “JONES NO. 1 1936”. The surveyor measured the direction and distance from the triangulation station to the Reference Mark (RM) and recorded the information as part of the station’s description. Later, if a surveyor attempting to find a Triangulation Station stumbled upon a RM first, the arrow and the published distance and direction between the RM and station would be valuable aids in the station recovery. To check the position of the Triangulation Station, the new surveyor could measure the angles and distances to the Reference Marks and compare them to the original values. USC&GS specified a Reference Mark as early as 1913. By the 1920’s, two Reference Marks per Triangulation Station were specified. Reference Marks were usually set within 30 meters (one tape length) of the station. Reference marks were numbered clockwise from north and set about 90 degrees apart. If a RM was destroyed, a new Reference Mark would be set using the next consecutive number. The disks would be set in a concrete monument buried in the ground, or set in a drill-hole in a large structure or bedrock. This type of disk was used from about 1913 to about 1970. Although the distance and direction provided enough information to compute the positions of the RMs, it was not standard procedure to compute them. After about 1970, National Geodetic Survey REFERENCE MARK disks were used.

 

AZIMUTH MARKS – Beginning in 1927, a third Reference Mark, or long RM, was set about ¼ mile away from a station. They provided a starting azimuth (direction) for local surveys and for determining magnetic declination (difference between true north and magnetic north). Standard Azimuth Mark disks replaced azimuth reference marks about 1935. Also in 1935 the precision of the directions to Azimuth Marks was increased by changing the number of repetitions of the angle measurements from two to four. Azimuth Marks visible from the ground at the main triangulation station had been frequently requested by local surveyors and engineers. Azimuth Marks were factory stamped with “AZIMUTH MARK” and with an arrow. The original surveyor stamped the Triangulation Station’s name and date on the Azimuth Mark disk, just prior to setting. Since this is the exact same stamping as on the Triangulation Station disk, persons recovering the mark must check the factory stamping of “AZIMUTH MARK” (with arrow) versus “TRIANGULATION STATION” (with triangle) to determine which is which. When set, the surveyor rotated the Azimuth Mark disk until its arrow pointed directly toward the Triangulation Station disk. The surveyor then measured the direction, and in later years distance, to the Azimuth Mark (from the Triangulation Station) and recorded the information. Measuring the distance to the Azimuth Mark began in the mid 1970’s when electronic distance measuring equipment came into common usage, and underground marks were set at many of these. Azimuth Marks were usually set between ¼ mile and 2 miles from the Triangulation Station, at a location that was visible from tripod height at the Triangulation Station, and generally in or near a fence line along a road. The Azimuth Mark was included in the “To Reach” portion of the station’s description. The distance to most Azimuth Marks was measured with an odometer, so most don’t have adjusted positions and many are a challenge to recover. The disk would be set in a concrete monument buried in the ground, or set in a drill-hole in a large structure or bedrock. This type of disk was used from about 1935 to about 1970. After about 1970, National Geodetic Survey AZIMUTH MARK disks were used.

 

Are the Benchmarks referenced to a master Benchmark or position?

 

thanks, Sam

0

Share this post


Link to post

Sam, Please define what types of survey marks you are including in the term "bench marks". Different people use different definitions.

 

Thanks,

GeorgeL

NGS

0

Share this post


Link to post

Wow! Great info and it may explain what I spotted recently in Portland, ME. I was at the Portland Head Lighthouse and spotted two Benchmarks, labeled National Ocean Survey. I attempted to log them on Geocaching.Com but there's no PID associated with these two marks. The ID on them ends with A for one and B for the other. I looked around and did not see either a "C" or another Benchmark. A and B are only a very short distance apart. Does this jive NGS Surveyor?

0

Share this post


Link to post

Fireman88, Those survey disks you found are tidal bench marks. They are different from geodetic bench marks and are in a different database, see this database for tidal bench marks: http://tidesandcurrents.noaa.gov/station_r...ark+Data+Sheets. Tidal bench marks are tied by differential leveling to a nearby tide gauge. Geodetic bench marks are tied by differential leveling to a nation-wide vertical datum.

 

For more information, see my paper on survey marks at: http://www.ngs.noaa.gov/web/about_ngs/hist...dexhUSCGS.shtml , and scroll down to "Bottles, Pots, and Pans: Marking the Surveys of the U.S. Coast & Geodetic Survey and NOAA", and click on it.

 

GeorgeL

NGS

0

Share this post


Link to post

Deleted per request

Edited by tjkelly92
0

Share this post


Link to post

I was curious as to what the benchmarks might look like after I went looking for some today. All three of the ones I found looked different. After doing a search, but before looking through the forum, I found a site that gave me a really nice array of pictures of what I might find. I thought I would share it here.

 

http://www.landsurveyor.us/gallery_c1.htm

0

Share this post


Link to post

Thank you for that info. I am currently trying to find just what you described. I know the station disk is there, I talked to a rancher who said he recently saw it, but neither one of us could find it. I forgot my probe and the next time out I will take it and the metal detector to see if I can locate the station marker, then go from there. Thanks again.

0

Share this post


Link to post

Very informative article. Thanks for sharing it!

0

Share this post


Link to post

Thanks for this Benchmark lesson! I feel informed! I've found 10 to date, including: 1 Triangulation Station, 1 Monument, 1 Elevated Tank, 1 Vertical Control Disk, 5 general Benchmark disks, and 1 with unspecified type. I didn't know what all that ment before, but now I do!

 

I'm interested in finding these, mostly because most of them were set almost 80 years ago! Whenever we go caching somewhere, I look up the local benchmarks and load the LOC file into my GPSr. If there's a BM close to a cache, we'll try to find it! I just wish you could upload a GPX file with the type of BM and NGS description instead of just the coords. That would be nice. Also, I wish Groundspeak would promote benchmark hunting a little more. Maybe have a 'Caches Found' score/number, a separte 'Benchmarks Found' score/number, and then a 'Total Found' score/number.

 

Thanks again for the information!

 

Jordan

p.boy

#|:•D

Edited by p.boy
0

Share this post


Link to post

I have just recently found out about these when searching for locationless caches. The reason I was looking for locationless caches was that I accidently found a cache when out attempting to hide one. It must be part of a puzzle was my first answer so I am doing all the puzzle caches in my area in order to find it. No luck however, yet.

Back to benchmarks though. I found some that were close to home and logged them in Waymarking.com as there didn't seem to be a place under Geocaching.com. I see benchmarks listed in some people's profiles though. How is this possible? I live in Canada and some of them were Canadian ones besides the American ones they had found. Any help?

 

Thanks

0

Share this post


Link to post

I have just recently found out about these when searching for locationless caches. The reason I was looking for locationless caches was that I accidently found a cache when out attempting to hide one. It must be part of a puzzle was my first answer so I am doing all the puzzle caches in my area in order to find it. No luck however, yet.

Back to benchmarks though. I found some that were close to home and logged them in Waymarking.com as there didn't seem to be a place under Geocaching.com. I see benchmarks listed in some people's profiles though. How is this possible? I live in Canada and some of them were Canadian ones besides the American ones they had found. Any help?

 

Thanks

 

The URL is www.geocaching.com/mark, or you can click the link at the wayyyy bottom of the page under "More". Click advanced search to search by coordinates.

0

Share this post


Link to post

In the on-line NGS data I was recently able to track down station "DAVE 1974", set on the East shore of Knik Arm in Alaska's Cook Inlet.

 

NAD 83(1986)- 61 18 28.61167(N) 149 49 10.59919(W) Elevation 23.1 ft

 

I helped set this station in 1974 while working as a survey crewman on the NOAA Ship Rainier and the team named it after me. Pretty neat to track it down after all these years.

 

Dave

0

Share this post


Link to post

My 'caching friend & I found one today that neither of us can find on any database (nor do we know how to do this); we both forgot to get the coords (They're approx. 300' NNW of N34° 31.699 W112° 24.722), but took pics of the pipe cap marker. Markings were:

 

[around the outer perimeter of the pipe cap]:

U.S.GENERAL LAND OFFICE SURVEY-192

[inside that]:

PENALTY $250 FOR REMOVAL

[in the center area]:

13NT13N

S1 | R1W

___|

S12 |

R2W S7

 

How can we log this as a find, and more specifically, where do we look?

Edited by AeroMechAZ
0

Share this post


Link to post

My 'caching friend & I found one today that neither of us can find on any database (nor do we know how to do this); we both forgot to get the coords (They're approx. 300' NNW of N34° 31.699 W112° 24.722), but took pics of the pipe cap marker. Markings were:

 

[around the outer perimeter of the pipe cap]:

U.S.GENERAL LAND OFFICE SURVEY-192

[inside that]:

PENALTY $250 FOR REMOVAL

[in the center area]:

13NT13N

S1 | R1W

___|

S12 |

R2W S7

 

How can we log this as a find, and more specifically, where do we look?

 

AeroMechAZ, what you found is a section corner from the Public Land Survey System. Very few of these boundary monuments are included in the database of geodetic survey monuments maintained by the NGS, a circa 2000 snapshot of which is used by geocaching for its database of benchmarks. If you'd like to log this, I believe there is a category for these on Waymarking.

0

Share this post


Link to post

AeroMechAZ, what you found is a section corner from the Public Land Survey System. Very few of these boundary monuments are included in the database of geodetic survey monuments maintained by the NGS, a circa 2000 snapshot of which is used by geocaching for its database of benchmarks. If you'd like to log this, I believe there is a category for these on Waymarking.

 

I also found a US General Land Office Survey 1933 disk - this one was in the desert near the Las Vegas Speedway. Looking forward to logging this; thanks for the guidance. I'm somewhat new to geocaching, and had not explored way marking. Benchmarking is, by far, the funniest part of caching (for me).

0

Share this post


Link to post

Wow! Great info and it may explain what I spotted recently in Portland, ME. I was at the Portland Head Lighthouse and spotted two Benchmarks, labeled National Ocean Survey. I attempted to log them on Geocaching.Com but there's no PID associated with these two marks. The ID on them ends with A for one and B for the other. I looked around and did not see either a "C" or another Benchmark. A and B are only a very short distance apart. Does this jive NGS Surveyor?

 

But many tidal bench mark disks are cross used as geodetic bench mark disks and are in the bench mark data base.

0

Share this post


Link to post

Wow! Great info and it may explain what I spotted recently in Portland, ME. I was at the Portland Head Lighthouse and spotted two Benchmarks, labeled National Ocean Survey. I attempted to log them on Geocaching.Com but there's no PID associated with these two marks. The ID on them ends with A for one and B for the other. I looked around and did not see either a "C" or another Benchmark. A and B are only a very short distance apart. Does this jive NGS Surveyor?

 

But many tidal bench mark disks are cross used as geodetic bench mark disks and are in the bench mark data base.

 

With a little help from U-Smart I found the info for the tidal benchmarks at that lighthouse, which aren't in the NGS database:

http://tidesandcurrents.noaa.gov/benchmarks/8418031.html

 

I'm not sure, but I think they may not be in use anymore. (A link that should have taken me to station 841-8031 took me to 841-8150. I then did a search on that site for 841-8031 and got to the above page.)

0

Share this post


Link to post

94aa608b-dc52-40e0-b553-1d9bdbcf7757.jpg

 

I didn't have any benchmarks loaded for my visit. (But my brother wanted to visit the old caches in Maine.) I only spotted the one mark.

0

Share this post


Link to post

Recovered a cool Gravity Reference Mark in North Florida, BE0315. The last one I tried to find had been recently taken from its monument.

0e96fe6b-d425-4aad-8355-52185e94d6b9.jpg

Edited by Gungadoy
0

Share this post


Link to post

Just recovered this rare USCGS Magnetic Station disk in Florida after 78 years of not being logged. It may be the only recovered magnetic in Florida. AR1564.

AR1564-ARCHER_MAGNETIC_STATION-1-20150224.jpg

Edited by Gungadoy
0

Share this post


Link to post

Just recovered this rare USCGS Magnetic Station disk in Florida after 78 years of not being logged. It may be the only recovered magnetic in Florida. AR1564.

AR1564-ARCHER_MAGNETIC_STATION-1-20150224.jpg

That's a great find! And the length of time between logs is exceptional in your case for this station. I've only recovered one magnetic station in my home state of Oregon and of all places, my alma mater, Oregon State University campus (which has a great Surveying program BTW) . I recovered it buried under grass and mud in a large grassy area where I used to throw the frisbee around 20 years earlier.

0

Share this post


Link to post

Just recovered this rare USCGS Magnetic Station disk in Florida after 78 years of not being logged. It may be the only recovered magnetic in Florida. AR1564.

AR1564-ARCHER_MAGNETIC_STATION-1-20150224.jpg

That's a great find! And the length of time between logs is exceptional in your case for this station. I've only recovered one magnetic station in my home state of Oregon and of all places, my alma mater, Oregon State University campus (which has a great Surveying program BTW) . I recovered it buried under grass and mud in a large grassy area where I used to throw the frisbee around 20 years earlier.

 

Hunting for benchmarks just for private fun got me into Geocaching but I had no idea this was so big! Thanks for the info!

0

Share this post


Link to post

Please sign in to comment

You will be able to leave a comment after signing in



Sign In Now
Sign in to follow this  
Followers 8