NGS Surveyor

In the late 1970s we were instructed not to stamp “RESET” on a horizontal mark. We used the specifications now on-line at: http://www.ngs.noaa.gov/web/about_ngs/hist...ntrol_Marks.pdf . Case III on page 5 describes the situation that PapaBear mentioned – stamping the name, the original date and the current date when a disk is set again in the original location. Case IV gives the specs. for setting a new disk nearby but not in the exact same location. Keep in mind that the date of this publication is 1968. An earlier version of these specs. is in Special Publication No. 247, 1959, page 86. GeorgeL NGS

The correct stamping is a good indicator, but here are two cases where the stamping may agree and you still have the wrong disk: 1. You found the Azimuth Mark. The stamping on the triangulation station (main mark) and the azimuth mark is supposed to be exactly the same. So, one has to look at the factory stamping (TRIANGULATION STATION versus AZIMUTH MARK) and the symbol in the center of the disk (triangle versus arrow). 2. You found a disk set by another agency with the same name. The year would most likely be different, but there are many cases where the name of the station is the same on two different agency's disks. GeorgeL NGS

I had just gotten a job with a surveying firm in Ohio. The boss was planning a survey for the next week and needed to tie it into the national network. He send me out to find a USC&GS triangulation station on a farm. He handed me the description and, I thought, no problem. I drove to the farm, obtained permission and walked to the fence line mentioned in the description. Then I realized the problem. The two RMs were in the fenceline BUT THE STATION WAS OUT IN THE MIDDLE OF THE PIG STY!!!!. We measured from the RMs, dug down a foot or so and found the mark. I never did know if the boss used the mark... or if it was some sort of initiation! The year was about 1974. GeorgeL NGS

Patty, Yes, those NOAA articles were written in 2007 as part of the 200th Anniversary Celebration. I didn't write any of them but I did review several prior to publication. There is a tremendous amount of information on the "Celebrating 200 Years" web site. billwallace, If you want to see lots of drawing of the flattened earth, and maybe learn some more about geodesy, see "Geodesy for the Layman" at: http://www.ngs.noaa.gov/PUBS_LIB/GeoLay.pdf GeorgeL NGS

I'll do some checking on the status of these and let you all know - it may be after Christmas. GeorgeL NGS

I organized the web site you found. Quite a few more have been set since the web site was created about 2 years ago. Just yesterday I was talking to our field surveyor that has been setting most of these commemorative marks. He has photos on the new ones but they are not yet on-line. Also, I don't know if all of the marks on the web site have been surveyed. So, some may not yet be in the database. All that said, these are beautiful marks, many of them are about 12 inches in diameter, and most are one-of-a kind. GeorgeL NGS

I am pleased to announce that we have three winners of the Survey Mark Quiz. First place goes to “Bill93”, second place to “m&h”, and third place to “billwallace”. Congrats to all! More good news, everyone passed and the average grade was 81.25%. No one got 100% however. I did an analysis to see which questions were answered incorrectly most often. Question #1 was the worst, followed by questions #23 and #27. There were 16 questions that everyone got correct. Here are the correct answers (at least my opinion) and some brief comments. 1. In which time frame were the first survey disks set in the U.S. by any agency? A. 1810-1819, B, 1850-1859, *C. 1870-1879, D. 1900-1909. The key words in the question are “..by any agency?” Verplanck Colvin set survey disks in the Adirondack Mountains during the 1870’s as the Superintendent of the Adirondack Survey (New York State agency). In fact, the earliest USC&GS disks (1900) bear a striking resemblance to Colvin’s disks. See page 9 of my paper on survey marks at: http://www.ngs.noaa.gov/web/about_ngs/hist...ey_Mark_Art.pdf and: http://www.colvincrew.org/verplanck-colvin . 2. What is the definition of a bench mark? A. Any point in the Geocaching or National Geodetic Survey databases, B. Any survey disk, *C. A mark with a known elevation above or below a certain datum, D. A brand of booze. Glad to report that no one selected “D” - everyone got this one correct!! 3. The Bilby Tower was first used in the year: A. 1870, B. 1900, C. 1917, *D. 1927. It was designed by Jasper Bilby in 1926 based on the common windmill towers, and first used in 1927. The last tower built by this agency was built in 1984. For a photo of one of the first towers built, see: http://usasearch.gov/search?v%3aproject=fi...amp;rpaid=& 4. A “Base Line” is: A. A line between two survey points that is carefully measured for use on controlling the scale of triangulation, B. A line between two survey points that is carefully measured and used to calibrate electronic distance measuring instruments, *C. Both of the above, D. Neither of the above. 5. Which if the following is not a standard height for a Bilby Tower: A. 37, B. 50, *C. 63, D. 103. The standard heights were 24, 37, 50, 64, 77, 90, 103, 116, and 129 (discontinued). The most common heights were 77 and 90 feet because these heights would get above most trees and also provide enough height to help compensate for the curvature of the earth. These heights were to the top of the inner tower – the height of the instrument. The light plate at the very top of the outer tower was 10 feet higher. Note, the tower leg sections were 13 feet, 8.5 inches long so that the heights could be varied at the above intervals depending on the reconnaissance work done ahead of time by a reconnaissance party. The leg sections overlapped and were joined by two bolts. The section length, this overlap, and rounding to the nearest foot caused the height differences to not be exactly 13 feet and caused the 14 foot difference between the 50 foot tower height and the 64 foot height. The 1965 version of the manual for Bilby Towers is on-line at: http://docs.lib.noaa.gov/rescue/cgs_specpu...5U352no62-3.PDF . This document contains excellent photographs and drawings. 6. Which of the following were used as survey marks by the USC&GS: A. Bottles, B. Wooden stakes, C. Nails, *D. All of the above. 7. Which of the following types of USC&GS survey disks had arrows on them? A. Reference marks, B. Azimuth marks, C. Gravity reference marks, *D. All of the above. 8. Which of the following were used to measure distances by the USC&GS/NGS? A. A chain, B. A rod in an ice bath, C. A laser, *D. All of the above. 9. The first survey disks used by the USC&GS were: A. Flat on top, *B. “Cup” shaped, C. Convex on top, D. None of the above. 10. A tower such as a church spire, radio mast, or water tank which has been surveyed is called a: A. Bench mark, B. Survey mark, *C. Intersection station, D. None of the above. I guess this is one of my “pet peeves” – when people refer to “Intersection Stations” as “Bench Marks”. 11. Most USC&GS survey disks were set between the years: A. 1807 – Present B. 1880 – 1970 *C. 1900 – 1970 D. 1910 – present. 12. National Ocean Survey (later National Ocean Service) disks were set to mark: A. Tidal bench marks, B. Third-order horizontal points for hydrographic surveys, C. Airport surveys, *D. All of the above. 13. Reference marks are generally within ______ meters of the triangulation station. A. 10, B. 20, *C. 30, D. 40. Because 30 meters (or 100 feet) is the length of many measuring tapes. 14. USC&GS or NGS survey disks have been made of: A. Brass/bronze, B. Iron/steel, C. Aluminum, *D. All of the above. 15. A USC&GS disk with a circle in the center could mark a: A. Topographic Station, B. Hydrographic Station, C. Bench Mark, *D. All of the above. 16. The rarest USC&GS disk is probably the: A. Hexangle shaped Gravity disk, B. “Cup” shaped triangulation station disk, C. Magnetic station disk with 6-pointed star, *D. Hexangle shaped Gravity reference mark disk. Our current NGS “gravity guy” told me he has only ever seen 1 or 2 of these. I have never seen even one. 17. Which of these is usually the only one with a horizontal position? A. MAGNETIC STATION, B. GRAVITY STATION, C. BENCH MARK, *D. TOPOGRAPHIC STATION. Topographic Stations have third-order horizontal positions, formerly used to control shoreline mapping. 18. Which of these types of disks may have an underground mark beneath it? A. TRIANGULATION STATION, B. REFENCE MARK, C. AZIMUTH MARK, *D. All of the above During the 1970’s it was common practice to set underground marks at Azimuth Marks (because the Azimuth Marks were positioned then). Underground marks at Reference Marks were rare but were set at one point in time. 19. Survey disks are set: A. Above ground level, B. Below ground level, C. Flush with the ground, *D. All of the above. 20. Which of the following types of disks do not have a blank spot for stamping the elevation? A. BENCH MARK with 3 crossed slashes, B. TRAVERSE STATION, C. USC&GS AND STATE SURVEY, *D. GRAVITY STATION. 21. Which of the following symbols used in the center of a disk were not used on a BENCH MARK disk? A. Slash, B . Circle, C. Three crossed slashes, *D. Triangle. 22. Which of these USC&GS disks did the NGS HORIZONTAL CONTROL MARK not replace? A. TOPOGRAPHIC STATION, B. HYDROGRAPHIC STATION, *C. GRAVITY STATION, D. TRAVERSE STATION. The Topo. Sta., the Hydro. Sta. and the Traverse Stations were all set and surveyed to provide horizontal positions. 23. Which of these following disk symbols were used to mark horizontal control points? A. Triangle, B. Circle, C. Cross, *D. All of the above. USC&GS Topographic Station disks and Hydrographic Station disks have circles in the center. “Topo” disks were used for horizontal control for shoreline mapping and airport surveys, and “Hydro” disks were used for horizontal control of hydrographic surveys. These surveys were mainly third-order, and positioned from higher order triangulation stations. NOS disks used for horizontal control have a “+” in the center. 24. When searching for a survey mark on a hill top, look for: A. Highest point, B. Point with best visibility around the horizon, C. Place where you would have set the mark, *D. All of the above. Hilltop points would almost always be triangulation stations (its too time consuming to level to the top of a tall hill or mountain). All three factors apply. 25. When looking for a bench mark (vertical point), consider: A. Mark spacing along the level line, B. Exposed bedrock, C. Clues in the Description, *D. All of the above. 26. Which of the following is not true about Reference Marks? A. Disks have arrows pointing to the Triangulation Station, B. Marks usually less than 100 feet from the Station, *C. Always higher than the Station, D. Station Description contains the distance and direction from the Station to the RMs. 27. Which of the following usually do not have an accurate horizontal position? A. GRAVITY STATION, B. MAGNETIC STATION, C. BENCH MARK, *D. All of the above. This is the third of the most commonly missed questions. Gravity Stations, when originally set, usually have only gravity information, Magnetic Stations have magnetic information and Bench Marks have elevations. Later, any of these might be surveyed again as part of a triangulation project and given an accurate horizontal position. 28. The most important factor in a close-up photograph of a survey mark: A., No debris covering mark, *B. All stamping is clear and legible, C. Even lighting, D. Disk fills most of photo. 29. Which of the following is not needed when recovering a survey mark? A. Station Description, *B. Hammer, C. Tape measure, D. Magnetic compass. A hammer is sometimes useful, but is the least essential of the four. 30. Which of the following is not a parameter for setting a concrete mark: A. Four feet deep, B. Twelve inches in diameter, *C. Rebar placed in concrete, D. Collar or form used around top portion of mark. We stopped putting magnetic materials in monuments many years ago. 31. Survey towers were made of: A. Steel, B. Wood, C. Aluminum, *D. All of the above. 32. Which of the following can be used to measure horizontal angles: A. Transit, B. Sextant, C. Theodolite, *D. All of the above. A sextant can be turned 90 degrees (flat with the horizon) and used to measure horizontal angles. In fact, fixes from two horizontal sextant angles were the method used for many years to position hydrographic survey launches. Angles were turned between a series of marked points (signals) along the shoreline. 33. Tools used to dig a hole for a concrete mark include: A. Auger, B. Post hole digger, C. Sharp-shooter shovel, *D. All of the above. 34. The back of a survey disk might contain: A. A Stem for setting in a drill hole in bedrock or a large structure, B. A Tube for mounting on a buried rod, C. A Collar for mounting on a pipe, *D. All of the above. 35. Which type of disk came in two shapes? A. MAGNETIC STATION, *B. GRAVITY STATION, C. HYDROGRAPHIC STATION, D. None of the above. 36. During the 1950’s and 1960’s, the number of disks set at a Triangulation Station was usually: A. 3, B. 4, *C. 5, D. 6. Station disk, underground station disk, RM1 disk, RM2 disk, and Azimuth Mark disk. 37. For many years, the specified distance range from the Triangulation Station to the Azimuth Mark was: A. 30 meters to 3 miles, B. 100 meters to 3 miles, *C. 1/4 mile to 2 miles, D. None of the above. 38. USC&GS disks were phased out of usage when NOAA was formed in: *A. 1970, B. 1971, C. 1972, D. None of the above. 39. The NGS disk that did not replace a USC&GS disk: A. HORIZONTAL CONTROL MARK, B. VERTICAL CONTROL MARK, C. GRAVITY MARK, *D. CALIBRATION BASE LINE. 40. The following types of aluminum logo caps were made (collar and lid to protect stainless steel rod marks): A. Vertical Control Mark, B. Geodetic control mark, C. Tidal Bench Mark, *D. All of the above. All three were made and we still use “B” and C”. Three winners - please email me your mailing addresses and I will mail your prizes. T-shirts, like the one awarded for first place, are available for sale by the U.S. Coast & Geodetic Survey Heritage Society. Let me know if you are interested. T-shirt graphics at: BM on front ( ) and the un-official USC&GS logo of an Eagle with a sextant on the back ( ). GeorgeL NGS

I don't recall a Table, but there is a "Quicktime" movie at: http://celebrating200years.noaa.gov/founda...ey_network.html , that shows the expansion of the horizontal network over time. The years with the most marks set were probably the 1930's when public work programs had many field parties setting and positioning marks. The movie is really interesting because you can see the progress of several important surveys like the Eastern Oblique Arc and the Transcontinental Arc of Triangulation. GeorgeL NGS

Don't forget, the deadline for entries is midnight, December 15th. GeorgeL NGS

Rockhounders, Your comment lit a light bulb here. We should have been discussing two different things. Triangulation station descriptions used to be quite different from vertical control station descriptions. I have been discussing triangulation station descriptions and your comment is about vertical control. See the following quote from NOAA Manual NOS NGS 3, Geodetic Leveling, page 2-40 (on-line at: http://www.ngs.noaa.gov/PUBS_LIB/Geodeticleveling_nos_3.pdf ): “The distance from the nearest city or town, which is to be entered on line *18*, is not a straight-line measurement. Instead, it is the total of the distances given in the instructions to reach the point, by following the most direct highway routes.” GeorgeL NGS

I just found out that program WINDESC (used to write station descriptions) computes airline miles from the 3 nearest towns. GeorgeL NGS

DesertDweller and Shirley, I did some looking on this question of air miles versus road miles. USC&GS Special Publication No. 247 doesn’t specify (see pages 119-120), but the contracting document that I wrote a few years ago reads: “2.1 FIRST PARAGRAPH - The first paragraph is the description of locality. This part of the description begins by referring to the airline distance and direction (cardinal or inter-cardinal point of the compass) from the three nearest well-known mapped geographic feature(s), usually the nearest cities or towns. Use three references equally spaced around the horizon, if possible. In writing the Description, always progress from the farthest to the nearest reference point. Distances in this part of the description shall be in kilometers (followed by miles), or meters (followed by feet), all distances to one decimal place. Detailed measurements which appear elsewhere in the description should not be repeated in this paragraph. Points of the compass should be fully spelled out. Do not use bearings or azimuths. State the name, address, and phone number of public sector property owners (however, phone numbers of private property owners are NOT included). State any advance notice and security access requirements for reaching the station. Also state any unusual transportation methods that may be required to reach the station.” My thinking is, that the main purpose of the distances from the nearest towns is to give the user some references for quickly determining the mark’s approximate position on a map. Remember, most of these descriptions were written long before on-line maps and GPS were available. Also, if a description gives a “cross-country” distance, like “8 miles southeast of Jones Mountain,” that would also be “air” miles. Once the description distances are clearly following roads, they become road distances. If there is a road due north (or east, etc.) of a town that leads right to the station, then the air miles and road miles would be the same, perhaps explaining why road miles have seemed to fit in some cases. GeorgeL NGS

To answer a question from some time ago, my original post in this thread was in response to posts I had seen on the Geocaching site. Sometimes when I see a post that is obviously in error, I send a polite email to the poster diplomatically pointing out the problem. Most of the time I get a quick and pleasant response saying that they will fix the problem. Unfortunately, I don't have the time to do this for all posts. GeorgeL NGS

Interestingly, I was Operations Officer on the PEIRCE a few years later. By 1981-83 we were using different electronic positioning systems, namely ARGO (long range) and Mini-Ranger(short range). GeorgeL NGS

Here are the NGS specs. for driving stainless steel rod marks: 11. Repeat step 10 (adding rod sections) until the rod refuses to drive further (anchored), or until a driving rate of 60 seconds per foot is achieved. In the event that the rod will not sufficiently slow down to meet desired driving rate, terminate upon reaching 90 feet (22.5 rods). This will leave about 2 feet of rod out of the hole. If possible, let the rod set overnight, then drive the remaining 2 feet of rod to determine whether driving rate has reduced. If rod feels secure in ground, use this depth even though minimum driving rate of 60 seconds per foot has not been met. If the rod turns freely in clockwise direction, contact NGS for a decision to drive additional rods. Sometimes, all that is necessary to achieve a well anchored rod is driving it a few more feet. In other instances an additional hundred feet may be required. Indicate in the written station description the depth of rod, and whether it was driven to refusal or met the slow driving rate. Also include a description of any unusual mark setting circumstances. On-line at: http://www.ngs.noaa.gov/ContractingOpportu.../PR_SOW_v9C.pdf, Attachment E: “Setting an NGS 3-D Monument”. GeorgeL NGS

SURVEY MARK QUIZ CHALLENGE Below are questions for a fun quiz I have prepared. There are 40 questions, concerning U.S. Coast & Geodetic Survey, National Ocean Service, and National Geodetic Survey survey marks. Some questions should be easy, some hopefully informative, and some have best answers that may not be one’s first guess. Read all questions carefully. Rules: This is an open book quiz. The first three sets of answers received with 100% grades, win prizes. If there are less than three perfect papers by December 15th, then the three highest grades win, but all winners must have at least 70%. Submit all entries to George.leigh@noaa.gov , subject line “Quiz”. The winners, the correct answers, and the overall average score will be announced, individual scores will not be published. First prize will be a newly designed USC&GS T-shirt with a brass-colored Bench Mark on the front ( ) and the un-official USC&GS logo of an Eagle with a sextant on the back ( ). Second and third place prizes will be USC&GS 200th Anniversary lapel pins ( ). 1. In which time frame were the first survey disks set in the U.S. by any agency? A. 1810-1819, B, 1850-1859, C. 1870-1879, D. 1900-1909. 2. What is the definition of a bench mark? A. Any point in the Geocaching or National Geodetic Survey databases, B. Any survey disk, C. A mark with a known elevation above or below a certain datum, D. A brand of booze. 3. The Bilby Tower was first used in the year: A. 1870, B. 1900, C. 1917, D. 1927. 4. A “Base Line” is: A. A line between two survey points that is carefully measured for use on controlling the scale of triangulation, B. A line between two survey points that is carefully measured and used to calibrate electronic distance measuring instruments, C. Both of the above, D. Neither of the above. 5. Which if the following is not a standard height for a Bilby Tower: A. 37, B. 50, C. 63, D. 103. 6. Which of the following were used as survey marks by the USC&GS: A. Bottles, B. Wooden stakes, C. Nails, D. All of the above. 7. Which of the following types of USC&GS survey disks had arrows on them? A. Reference marks, B. Azimuth marks, C. Gravity reference marks, D. All of the above. 8. Which of the following were used to measure distances by the USC&GS/NGS? A. A chain, B. A rod in an ice bath, C. A laser, D. All of the above. 9. The first survey disks used by the USC&GS were: A. Flat on top, B. “Cup” shaped, C. Convex on top, D. None of the above. 10. A tower such as a church spire, radio mast, or water tank which has been surveyed is called a: A. Bench mark, B. Survey mark, C. Intersection station, D. None of the above. 11. Most USC&GS survey disks were set between the years: A. 1807 – Present B. 1880 – 1970 C. 1900 – 1970 D. 1910 – present. 12. National Ocean Survey (later National Ocean Service) disks were set to mark: A. Tidal bench marks, B. Third-order horizontal points for hydrographic surveys, C. Airport surveys, D. All of the above. 13. Reference marks are generally within ______ meters of the triangulation station. A. 10, B. 20, C. 30, D. 40. 14. USC&GS or NGS survey disks have been made of: A. Brass/bronze, B. Iron/steel, C. Aluminum, D. All of the above. 15. A USC&GS disk with a circle in the center could mark a: A. Topographic Station, B. Hydrographic Station, C. Bench Mark, D. All of the above. 16. The rarest USC&GS disk is probably the: A. Hexangle shaped Gravity disk, B. “Cup” shaped triangulation station disk, C. Magnetic station disk with 6-pointed star, D. Hexangle shaped Gravity reference mark disk. 17. Which of these is usually the only one with a horizontal position? A. MAGNETIC STATION, B. GRAVITY STATION, C. BENCH MARK, D. TOPOGRAPHIC STATION. 18. Which of these types of disks may have an underground mark beneath it? A. TRIANGULATION STATION, B. REFENCE MARK, C. AZIMUTH MARK, D. All of the above. 19. Survey disks are set: A. Above ground level, B. Below ground level, C. Flush with the ground, D. All of the above. 20. Which of the following types of disks do not have a blank spot for stamping the elevation? A. BENCH MARK with 3 crossed slashes, B. TRAVERSE STATION, C. USC&GS AND STATE SURVEY, D. GRAVITY STATION. 21. Which of the following symbols used in the center of a disk were not used on a BENCH MARK disk? A. Slash, B . Circle, C. Three crossed slashes, D. Triangle. 22. Which of these USC&GS disks did the NGS HORIZONTAL CONTROL MARK not replace? A. TOPOGRAPHIC STATION, B. HYDROGRAPHIC STATION, C. GRAVITY STATION, D. TRAVERSE STATION. 23. Which of these following disk symbols were used to mark horizontal control points? A. Triangle, B. Circle, C. Cross, D. All of the above. 24. When searching for a survey mark on a hill top, look for: A. Highest point, B. Point with best visibility around the horizon, C. Place where you would have set the mark, D. All of the above. 25. When looking for a bench mark (vertical point), consider: A. Mark spacing along the level line, B. Exposed bedrock, C. Clues in the Description, D. All of the above. 26. Which of the following is not true about Reference Marks? A. Disks have arrows pointing to the Triangulation Station, B. Marks usually less than 100 feet from the Station, C. Always higher than the Station, D. Station Description contains the distance and direction from the Station to the RMs. 27. Which of the following usually do not have an accurate horizontal position? A. GRAVITY STATION, B. MAGNETIC STATION, C. BENCH MARK, D. All of the above. 28. The most important factor in a close-up photograph of a survey mark: A., No debris covering mark, B. All stamping is clear and legible, C. Even lighting, D. Disk fills most of photo. 29. Which of the following is not needed when recovering a survey mark? A. Station Description, B. Hammer, C. Tape measure, D. Magnetic compass. 30. Which of the following is not a parameter for setting a concrete mark: A. Four feet deep, B. Twelve inches in diameter, C. Rebar placed in concrete, D. Collar or form used around top portion of mark. 31. Survey towers were made of: A. Steel, B. Wood, C. Aluminum, D. All of the above. 32. Which of the following can be used to measure horizontal angles: A. Transit, B. Sextant, C. Theodolite, D. All of the above. 33. Tools used to dig a hole for a concrete mark include: A. Auger, B. Post hole digger, C. Sharp-shooter shovel, D. All of the above. 34. The back of a survey disk might contain: A. A Stem for setting in a drill hole in bedrock or a large structure, B. A Tube for mounting on a buried rod, C. A Collar for mounting on a pipe, D. All of the above. 35. Which type of disk came in two shapes? A. MAGNETIC STATION, B. GRAVITY STATION, C. HYDROGRAPHIC STATION, D. None of the above. 36. During the 1950’s and 1960’s, the number of disks set at a Triangulation Station was usually: A. 3, B. 4, C. 5, D. 6. 37. For many years, the specified distance range from the Triangulation Station to the Azimuth Mark was: A. 30 meters to 3 miles, B. 100 meters to 3 miles, C. 1/4 mile to 2 miles, D. None of the above. 38. USC&GS disks were phased out of usage when NOAA was formed in: A. 1970, B. 1971, C. 1972, D. None of the above. 39. The NGS disk that did not replace a USC&GS disk: A. HORIZONTAL CONTROL MARK, B. VERTICAL CONTROL MARK, C. GRAVITY MARK, D. CALIBRATION BASE LINE. 40. The following types of aluminum logo caps were made (collar and lid to protect stainless steel rod marks): A. Vertical Control Mark, B. Geodetic control mark, C. Tidal Bench Mark, D. All of the above. Good Luck, GeorgeL NGS

I was, of course, kidding when I said to drill a hole in the tree. When a measurement to the center of a tree or pole was desired, we measured to the side as jwahl also described. When traversing to a large diameter tank, we would tape to the edge, then measure the circumference, compute the radius, and add the radius to the distance measured to the edge of the tank. GeorgeL] NGS

Measure the circumference. Divide by Pi. Divide by 2 to get the radius. Then drill a hole exactly that depth and in-line with the direction to the other mark. Use a long screwdriver to hold the end of the tape at the bottom of the hole. OR Measure from the side of the tree. GeorgeL NGS

I sent emails to 3 retired friends of mine who all worked on NGS field parties. No one remembered a specification stating "nearest point" or "center of...". One stated that the person writing the description should always state what they are measuring from, and another found a CO-OPS (NOAA tide gauge office) spec. that instructs one to measure to the center. As I stated earlier, I could not find the answer in the several USC&GS and NGS specs. I looked in. GeorgeL NGS

My Garmin Nuvi has, in addition to its automobile mode, a bike mode, and a pedestrian mode. So, you can drive close to the station, and then remove your Nuvi from your car, switch to pedestrian mode, and start walking. I have done this once and it worked very well. GeorgeL NGS

I searched through several USC&GS and NGS publications and could not find the answer to your question. Here is what I did find: A quote from page 120 of Special Pub. #247, Manual of Geodetic Triangulation: “(6) Details of individual marks.-This section should give a short description of the station mark, each reference mark, and the azimuth mark. The exact stamping on each mark, the amount it projects above the surface or is covered by the ground, and the type of mark should be stated. The detailed location of each mark should include measurements from definite objects in the vicinity such as witness posts, center lines of roads, fences, ditches, power poles, prominent trees, wells, houses, barns, cairns, and shorelines. If slope distances were measured, they should be stated in this paragraph. Horizontal measurements listed in the box section should not be repeated here.” The center of roads was specified since roads are often widened and because the edge of some roads is poorly defined. From NGS’ “Geodetic Operations” manual, of 1984, page 2.1-4 (not on-line): “Reference distances from monuments to prominent objects should usually be measured and recorded to the nearest tenth of hundredth of a meter, depending on the distinction of the point measured to. Distances to and between reference marks must be measured to the nearest millimeter and the nearest hundredth of a foot.” GeorgeL NGS

Thanks for all the positive comments and helpful suggestions. None of the content is intended to set a requirement, but rather to help find survey marks. I will attempt to answer some of the comments/questions: Pgrig – Good ideas. 2Jeeps2Jacks – Good ideas, but more equipment to lug around. I never had a distance wheel to use. Instead, I practiced and practiced my pacing. You can do this by laying out 100, 200, or 300 or more feet on level ground and walk it multiple times, trying hard to keep to your “normal” pace. Then average your results and come up with a simple formula to convert paces to feet. I still remember mine: divide the distance in feet by 3 and add 10% of the result. So, if I wanted 100 feet I would pace 33.3 paces plus 3 paces or a total of 36.3 paces. Reflective vest definitely a good idea along a road. I have never used a metal detector to search for a survey disk. I imagine it would be very helpful for difficult stations, but again, more equipment to carry. Bill93 – Some USC&GS/NGS marks had a magnetic or rebar imbedded in the concrete, but most don’t. 2oldfarts – It was written for my work (read professional surveyors), but amateurs can use whichever parts are helpful. Regarding the broken tile, etc, that quote is from a 50-year old reference and was intended to provide a possible clue and to explain how it used to be done, not how it should be done now. Same comment on the “verified by 2 other people” – that was written 50 years ago and was not meant to set a present day requirement. Black Dog Trackers – Good ideas on distance and angle conversions, I will add something. On the photos, I’m with you. I don’t understand why people cover up a portion of the survey mark with their GPSr. On the metric conversion, I memorized 3.280833333 over 30 years ago and still remember it. Also, there is little chance of applying it backwards. Remember, this is the conversion for the U.S. Survey Foot. The conversion is slightly different for the International Foot, which some states use. For more information on the two definitions, see: http://www.ngs.noaa.gov/PUBS_LIB/ManualNOSNGS5.pdf , page 11-12. PFF – Good idea, I will add a comment about what the “white powder” is! \ GeorgeL NGS P.S. Watch for my survey mark quiz, almost ready for release.

I just completed a "cookbook" of instructions for recovering a survey mark for a work project. I consulted several sources, including the Geocaching "Frequently Asked Questions". See what you think. GeorgeL NGS ----------------- MARK RECOVERY INSTRUCTIONS A. DATASHEET - Obtain and study the mark’s datasheet (description), including all recovery notes, and highlight key points (such as: the number of reference marks, the distance from the edge of a road, etc.) and any flag any discrepancies found. U.S. Coast & Geodetic Survey and National Geodetic Survey (NGS) marks and some others are in the NGS database at: http://www.ngs.noaa.gov/cgi-bin/datasheet.prl . For a sample NGS datasheet, with explanations, see: http://www.ngs.noaa.gov/cgi-bin/dsformat.prl . Recent recoveries and photos of many marks can be found on the Geocaching.com web site. B. DATABASE SEARCH - Perform a NGS database search for other nearby survey marks (radial search at: http://www.ngs.noaa.gov/cgi-bin/ds_radius.prl . This information may be helpful in finding the intended mark and may help avoid confusion at the site. C. MAPS - Obtain maps, aerial imagery and/or satellite imagery of the area (paper or digital). D. COMPUTE POSITIONS - Recommend computing the positions of Reference Marks (RMs) and any other nearby marks, and consider computing the distances between RMs and any other marks. The “box score” on the datasheet lists the directions and distances to RMs and any other marks, and the “Forward” on-line software at: http://www.ngs.noaa.gov/TOOLS/Inv_Fwd/Inv_Fwd.html can be used to do the computation. Once “Forward” has been used to compute the positions, the “Inverse” software can be used to compute the distance between known points. E. PLOT - Recommend plotting all marks on the map and/or imagery at a scale to show surrounding features. Check features in the imagery against the description (near a road, on a hill top, etc.), and then attempt to resolve any discrepancies and contradictions. F. EQUIPMENT - Gather recovery equipment including: mark description, map, magnetic compass, 100 – 300 ft tape, shovel, long screwdriver (to hold one end of tape), whisk broom, camera, GPS receiver, scientific calculator, and, optionally, tile probe, metal detector. Also, a yellow crayon or white powder can improve the photos by highlighting the stampings. G. TRAVEL - To travel to the mark the original and “hard-core” way, travel to the beginning of the description’s “To Reach” and follow the “To Reach” using the vehicle’s odometer, and left and right turns as listed in the description. Otherwise, enter the position into the GPS receiver (GPSr) and follow the GPSr’s directions (making sure to use the NAD 83 or WGS 84 datum). H. PERMISSION - Request property owner permission as necessary. I. COMPLETE TRAVEL - Continue travel to the immediate vicinity of the mark and do a visual search for: 1. Reference objects mentioned in the description (edge of roads, bridges, buildings, fence-lines, telephone poles, etc.), 2. Witness Posts 3. Remains from previous occupations (wood, wire, slight depression, etc.) 4. Survey marks J. FIND - Use distances, angles, and other information from the description to narrow the search, (eg, the distance from a road or fence, witness post, reference mark, etc., the type of mark: concrete monument, disk in bedrock, etc.). If not found, review the datasheet for additional clues. K. MEASURE - Once some of the objects and/or marks are found, use a magnetic compass to determine the approximate directions and measure the distances by pacing or taping from the witness post, reference marks, and other reference objects. Mark the arc of each distance and intersect the distance arcs, as required. Use any vertical information provided, such as distance above or below road or railroad track. When using a magnetic compass be sure to correct for the magnetic declination (difference between true north and magnetic north). The value can be obtained from: http://www.ngdc.noaa.gov/geomagmodels/Declination.jsp . If the main station is found first, use a compass and pacing or taping to locate the RMs. If an RM is found first, use the direction of the RM’s arrow and the distance stated on the Datasheet to help find the main station. Also, the “Back Azimuth” from the “Forward” computation for that RM will provide the azimuth from the RM back to the Triangulation Station. L. GPS - Remember when searching using GPS that most vertical control points have only scaled positions with a 6 arc-second error tolerance (about 600 ft); the description may get you much closer to the mark than a GPSr with the scaled coordinates. Combine GPS results with other clues. Most horizontal control points have coordinates that are much better than a hand-held GPS receiver (GPSr). A hand-held GPSr may only be accurate to 6-8 meters, perhaps 1-2 meters if equipped with WAAS and if the WAAS signal is available. Thick trees are a definite challenge for a GPSr. (WAAS = Wide Area Augmentation System, operated by the FAA.) M. CHECK DESCRIPTION - For all marks found, check the description elements such as: (1) the name of the agency cast into the disk or logo cap, (2) the type of disk (RM, Azimuth Mark, etc.) cast into the disk, (3) the exact name and date stamped, and (4) the type of setting (bedrock, concrete, etc.). Check all information on the survey disk against what is stated on the Datasheet. Avoid false recoveries. Also avoid false “destroyed” notices. Note, and ideally resolve, any discrepancies. In the Recovery Note, list significant changes and discrepancies. N. GROUND CHECK - For all marks found, visually check them to see if they appear disturbed. Then check them by taping the distances between the marks and any other usable references, and compare them to published and computed values. Note the direction (to at least the nearest 45 degrees--NE, NW, etc.) from the main Triangulation Station to each RM. Note any significant differences from what is on the datasheet. A good check on distance measurements is to first tape in metric units, then tape in English units, and then use a calculator to convert and compare. There are 3.280833333 U.S. Survey Feet in one meter. O. PHOTOS - Clean the marks off completely and photograph the marks. Ensure adequate and even lighting. Close-up photos should be in sharp focus, and clearly and legibly show ALL the information cast into, and stamped onto, the disks. Also take photo(s) showing the surrounding area. TIPS: 1. Ask local residents for information, and permission, as necessary. 2. Once close to the triangulation station, go to the location where you would set a mark, where it would make sense (highest point, point with best view, exposed bedrock, etc.). 3. Marks originally positioned with GPS can be anywhere with good access and good sky visibility. 4. RMs are usually within 30 meters of the Triangulation Station, about the same elevation when possible, numbered clockwise from north, and about 90 degrees apart (around the Triangulation Station). 5. Older Bench Marks (vertical control points) are usually along a road or railroad, often set in a rock outcrop or bridge abutment. Newer, rod-type marks may be near the right-of-way fence along a road. 6. There may be signs of a previous survey, like old wooden boards or wire. In the Western U.S. some intact 4-foot wooden stands many years old have been found. 7. Ensure that the coordinates, map, and imagery are on the same datum (use NAD 83). 10. From the Description, determine if the Azimuth Mark is along the route to the main mark, and while enroute to the main station, watch for the mark and a possible Witness Post. 11. If the marks are still not found, consider using a metal detector and/or steel tile probe (long rod with handle). 12. Also consider construction in the area which may have destroyed the mark, or at least changed its setting considerably. Below is a quote providing instructions for recovery of survey marks that is from USC&GS Special Publication #225, from 1959, pp 81-83: “RECOVERY OF OLD STATIONS One of the duties of the reconnaissance engineer is to recover existing stations to which to connect his work. These are frequently stations of early surveys marked in a variety of ways and the descriptions may be inadequate or out-of-date. If the original marks are visible, people in the locality can usually point them out. If the surface indications are gone, the recovery often requires much patience and labor. Triangulation stations are ordinarily placed on high ground and in a country of definite relief the highest hill will usually be the site, the immediate vicinity of which can be located from the original description. If the type of soil permits, systematic sounding with a prodding bar may locate the subsurface mark or fragments of the surface mark. When reference and witness marks are noted in the descriptions, some trace of them may be found even for very old stations. A large tree noted in the original description may sometimes be evidenced by a rotting stump or log or by discolored soil. Old signal foundations may be indicated by slight depressions in the surface, by softness of the subsoil, or by penetration of top soil into the subsoil. No digging should be done until all surface indications have been studied. Digging for a subsurface mark over a large area is a large task and there may be objections by the landowner. Sometimes directions to tanks, chimneys, windmills, church spires, etc., which were observed when the station was established, can be duplicated by trial at the site and a close approximation to the station position thus found. Several subsurface marks have been recovered by the writer by this method after all surface indications had disappeared. In one instance, the directions on four church spires 6 to 15 miles away were duplicated with a 4-inch theodolite and the subsurface mark was found within 18 inches of the point thus determined. If solar observations are used to obtain the azimuths of the lines, it is possible to use this method when only two distant objects are visible. If a reference mark can be found, not too far from the station, the distance can be taped and the direction determined by magnetic compass. If the distance is fairly large, it can be determined by measuring a short base and two angles as explained on page 50 and the direction can be obtained by a solar observation. Many old stations were marked with tiles or pottery of various forms. If these marks have been broken, fragments of the materials remain in the top soil almost indefinitely and are of much aid in the recovery of the station. At many old stations broken tile, glass, charcoal, ashes, or other foreign substance was mixed with the soil at the station site. This was an excellent practice and should be revived. Any digging required to locate a station should be done with care. The subsurface marks at old stations are usually small and fragile, and can be easily broken or displaced by careless digging. For this reason, some experienced man should do the work. Dirt of one depth of the shovel should first be removed and the new surface inspected for foreign materials, voids, soft spots, and discoloration. An old excavation below plow depth will remain soft in most soils for many years, and topsoil penetration into the subsoil is a sure sign of previous disturbance. Such indications will often localize the digging at once. If it be necessary to go deeper, another layer is taken off and investigated in the same manner. Each shovel full of earth should be broken up to see if it contains any fragments or other evidence of the mark. Signs will often be found which will make it unnecessary to excavate the entire area under investigation to the full depth. If there are many rocks in the soil it is necessary to inspect each one before removing it to avoid accidentally destroying the subsurface mark. Sometimes, a little investigation with a knife blade and whisk broom will save a great amount of digging. Some knowledge of the methods used by the party that established the station will greatly aid the reconnaissance engineer and it is also useful to learn if possible how the station was destroyed. The loss of surface markings may be due to local developments, to a fill over the original surface, or to a thorough destruction by vandals. Cases arise in which it is impossible to recover a station with any reasonable expenditure of effort on the part of the reconnaissance party. It is then permissible to call for a test station in the immediate vicinity of the lost mark. If it appears probable that the subsurface mark may still be in place, the position of the test station may be determined by the triangulation party from the nearest recoverable stations and the distance and direction from the test station to the old station may be found by an inverse computation. The station can almost always be recovered in this manner if there are any remnants at all of the original marks. A regular reconnaissance description should be written for each recovered station, including a statement regarding the condition of recovered marks, a note covering any irregularities or displacement of the mark, and a recommendation for re-marking if that is necessary. A recovery card should be submitted for every established station visited even though it is not used in the proposed scheme.” DESCRIPTIONS: HERE IS A STATEMENT FROM USC&GS SPECIAL PUBLICATION #247, “MANUAL OF GEODETIC TRIANGULATION”, PAGE 116: “The description should be clear, concise, and complete. It should enable one to go with certainty to the immediate vicinity of the mark, and by the measured distances to reference points and the description of the character of the mark it should inform the searcher of the exact location of the mark and make its identification certain. It should include only essential details of a permanent character.” SP#247 ALSO REQUIRED THAT DESCRIPTIONS BE WRITTEN BY ONE PERSON AND CHECKED BY TWO OTHERS.

Perhaps what we need is a simple, short, introduction for beginners that is "pinned" at the top of the page. This 1/2 page or so would give the basics and include links to additional details. Beginners may be scared away by the many pages of details presently available. GeorgeL NGS

Incorrect ID I just reviewed the close-up photos of the many USC&GS and NGS survey marks submitted over the last few days. I found at least four which appeared to be incorrectly identified, that is, the data sheet and the information shown in the photo of the disk did not agree! For beginners, here are a few simple rules to use to verify that the survey disk found is indeed the one being searched for: 1. Is the setting agency the same (on the disk and on the datasheet)? 2. Is the type of disk the same (triangulation station, reference mark, bench mark, etc.)? 3. Does the stamped station designation (name) agree? 4. Does the stamped year agree with the datasheet’s date set? 5. Is the disk set the way it is described (in concrete, in bedrock, etc.)? 6. Do the distances to the reference marks agree? 7. Do the distances to the referenced objects agree (edge of road, fence-line, etc.)? 8. Does the rest of the description agree? All this leads to my second point. Many disk photos do not show all of the above information because the photo was taken with some portion of the disk obscured (by dirt, gravel, grass, twigs, snow, the GPSr, even the shadow of the GPSr! I’m working on a “cook book” for recovering survey marks. I’ll post it for comment when complete. GeorgeL NGS