Bill93

So does that mean we wait for notice that it is working (and how do we get notice?), and then re-submit anything that hasn't appeared, or will they find things already in queue to process?

I don't think I've posted this before. Someone took a few pictures while on a trip and another added more. There are more property corners than geodetic marks, but some of those, too. https://rplstoday.com/community/threads/japanese-corner-marks.325399/

If you've found a disk by accident and want to find a PID and data sheet, start here https://www.geocaching.com/mark/ pick Advanced Search Enter approximate latitude and longitude and search. If that comes up with something near, compare the agency name and stamping to see if it is the one you found. You can do something similar on the NGS web site, which may have new marks added since the Geocaching snapshot of their data base in about 2000/2001. With a US Geological Survey disk, the odds of it being in the National Geodetic Survey data base are small but significant. Only some fraction of those were measured to the standards and included in the NGS list. The USGS list is on paper in file cabinets and will never be on line, and they don't care much about recoveries.

This seems to be targeted at students in surveying and GIS programs, but I'm not sure it's limited to those. Applications close Feb 2. Find existing 1968 bench marks, run static GPS sessions, and report. http://ak-aug.blogspot.com/ Participants will engage in benchmark recovery, which includes: Reconnaissance: locating NGS passive control monuments via GIS and field work; Recovery: executing survey of recovered benchmark with proper documentation for submission to OPUS shared solutions; Report: submission of findings to NGS and DENA GIS Specialist.

Yes, I should check out the other processing options. Doesn't OPUS Projects require simultaneous measurements at multiple sites? I only have one good setup. I'm using a tripod and tribrach. I measure up on 3 places to the ground plane to check centering/leveling, and calculate back to ARP height above the mark. I've pasted a spreadsheet in the back of the field book to quickly give me the difference. I don't think I have any problem with repeatability of setups, because session results seem to match as well as the pk-pk values of a session. Fixed height would avoid the calculation and chance of blunder there, but would require me to get more hardware and figure out how you make it stable. It seems like you would either need a sliding sleeve for the rod if using a tripod (4 legs aren't stable), or have to be careful at balancing and carry weights with a bipod.

Last year I acquired a Trimble 4000sst receiver and accessories. It has gotten me some interesting measurements, but doesn't qualify for the NGS program for GPS on Benchmarks because it doesn't process enough parts of the GPS signal. Recently, I bought a slightly newer model, the 4000sse, which uses all the old accessories and does qualify for OPUS shared solutions which can be used for the GPS on BM program. These receivers can be bought on eBay occasionally for a few hundred dollars, but you need to know what all is needed in the kit and to distinguish the reasonable models from the totally obsolete. Here's the setup on a tri-station with old receiver. The newer one doesn't look much different. For those who don't know about OPUS, here's a summary: The receiver records measurements every 30 seconds, and stores them essentially as a time delay from each satellite in view. You download those into a computer file and after some waiting time for CORS and orbit data to be collected, you send it to a web site at NGS. They automatically process this against CORS station data. A few minutes later it emails you a report that tells you where you were and some measures of performance. The orbit data is either "Ultra Rapid" meaning relying on predictions and available within a few hours, "Rapid" meaning updated with real measurements the next day, or "Precise" which has been processed to the best possible estimate but 2 to 3 weeks after the fact. There are two processing options, OPUS-S or static for 2 hours to 48 hours, and OPUS-RS or rapid static for 15 minutes to 2 hours. The RS algorithm is better in some ways and lets you get away with the shorter sessions for some uses, but OPUS-S with at least 4 hours is needed for any NGS use of the data. I'm hoping that when the weather warms up I can do some OPUS shared solutions on benchmarks that NGS can use as they check their gravity model. I want to have checked my results on a couple HARN stations first. Today I got the results using final "precise" orbits for a 7-hour session on a point in my back yard, processed by OPUS-S and also split into 7 sessions of 1 hour each for OPUS-RS. Here are some plots I put together to compare results. There are effects that the processing doesn't know about, so the supposed 95% confidence limits only apply to some of the error sources and can't be taken at face value. But note that the horizontal grid is 1-cm squares and the vertical grid is 2 cm. All of the horizontal position outlines would fit comfortably on a US 5-cent piece.

A lot of work went into this project by Jerry Penry, Kurt Luebke, and friends. Introduction & links Survey discussion and pictures Wikipedia for background info: https://en.wikipedia.org/wiki/Black_Elk_Peak

https://www.shapeways.com/shops/triangulation

Phenomenal work! It must take a serious investment of time to get the detail right, and a not insignificant production cost. It reminded me of the equipment models a guy posted on the professional surveyors forum. He also makes practical things for his work. https://rplstoday.com/community/threads/more-printed-surveying-models.241503/ https://rplstoday.com/community/threads/got-my-1-4-scale-geodimeter-today.232161/ https://rplstoday.com/community/threads/i-received-my-christmas-ornaments.227217/

How does anyone amass such a collection? That's a large percentage of the styles in George Leigh's writeup. Plus a couple of USGS to boot.

As I think I understand it, you can define the horizontal datum origin and orientation independently of the vertical, but in order to add any other points to your data base using that datum, you have to have the scale factor to convert surface measurements to distances on the ellipsoid model. I.e., if you are at lat-lon A,B and go some measured surface distance and direction then you need to convert that to distance on the ellipsoid before finding a new lat-lon. The conversion factor depends on elevation. They didn't have a very good geoid model at the time so in order to define the elevations they assumed the geoid was at the ellipsoid at Meades Ranch. That slightly inaccurate conversion of elevations introduced a significant distance (hence lat-lon) error as they got further away from that initial point toward the coasts. One of the benefits of NAD83 was fixing that problem, using a better geoid model. Hope I got that right.

I decided to post the question in the professional forum and got an authoritative answer there, that explained why that statement is true. Following the explanation really tests your understanding of geodesy.

The current Wikipedia entry Geodetic Datum has a statement in a paragraph discussing NAD27: "The geoidal height at Meades Ranch was assumed to be zero." At first glance this makes no sense to me. I thought the horizontal datum was on the mathematical ellipsoid and would have no relationship to the geoid. Is there some small second order effect that causes an interaction of the vertical with NAD27 (or NAD83 either) that would need such an assumption at the time? I didn't find a data sheet for Meades Ranch, but look at the data sheet for KG0640 Meades Ranch Reset (NGS) (Geocaching, older data sheet) and note the NGVD29 elevation is within a meter of NAVD88, and the current geoid separation is more than 26 meters. Should that Wikipedia statement be deleted?

All of these that weren't updated are bench marks or triangulation stations. Ironically, although NGS generally doesn't want intersection station reports, they did accept one in July that I submitted because I thought I had potentially useful information. See NJ0770 (NGS) (Geocaching) as discussed in this thread. I had data for the intersection station, a triangulation station, and a RM for a triangulation station that showed a fairly consistent pattern of offset between the NAD83(1996) and NAD83(2011) coordinates in this area that is not modeled by the GEOCON2 conversion software, due to the fact that it is a long distance to the nearest stations having both classical and official GPS coordinate measurements to allow such a determination. While my work wasn't NGS quality it seemed significant.

I have reported via the NGS web site form on perhaps a dozen disks this summer. Of those, 5 have not been updated. Some from early July were and some weren't. Two of three that I submitted on the same day in September were updated a week ago and the third one still hasn't. Perhaps a couple of my reports included unconventional information that I thought was useful, or were pretty trivial (reporting wrong direction from witness post on mark set in 2014), so if they were editing closely someone might have rejected them. But some of these missing reports were pretty straightforward. Anyone else have this experience or insight into what's going on?

Very few elevation marks have an underground backup disk. I've seen some MORC data sheets that had a rivet below the pipe the disk was on, but that was not common practice for either USGS or C&GS/NGS. Only triangulation stations typically had underground disk. If your disk had an elevation stamped it was very likely USGS as C&GS/NGS did not stamp elevations as a regular practice. And only a small fraction of USGS disks were measured to the standards to get in the NGS data base. So I am not optimistic for you but wish you luck. --------- Edit: the locations of elevation marks were usually SCALED off a topo map, which might be good within a few yards where there were features on the map to compare to, but the the values were truncated (not rounded) to whole seconds of lat-lon. Thus you can figure that even if the disk was perfectly located on the map, you have up to 100 ft north and 75 ft of west of the coordinates to search. The way to find bench marks from the data sheet is to go to the lat-lon coordinates and then put the GPS away. Get out the tape, and measure from the features listed in the to-reach instructions on the data sheet.

https://rplstoday.com/community/threads/uscgs-historic-markers.327890/

I found an interesting disk in Grand Canyon Village, near the area where you change between east loop and west loop shuttles. It appears to have no PID so I scabbed it onto the nearest mark in this data base. I had never seen one quite like it, nor with so many agency stampings.

NJ0770 isn't anything special except for the history I have on it. Its position was probably within a foot or two of correct back in its day, and after roof work it probably still is. It is also mentioned in my recent post about finding the accuracy of local stations.

Your enthusiasm is good to see, and I note that you have been finding bench marks for a while. Your reports to NGS can be valuable to them. I hope you have picked up the "flavor" of the official recovery reports. All business, no "found while geocaching with a friend on Saturday between rainstorms" comments. Use "Found as described" or add any helpful information you can, such as "School building is now a community center", "Road realigned and disk now xx feet from center", "Railroad dismantled and used as recreational trail", "[item they measured from] is gone. Disk is xx feet NW of new culvert". If you didn't find it, add helpful comments about how the location has changed. Give handheld GPS coordinates in degrees, minutes, and seconds format for marks that only had SCALED coordinates before. Please, no comments about how far off the old coordinates were, and never give your coordinates for a mark with ADJUSTED coordinates because they are more accurate than your device. Intersection stations (church spires, towers, water tanks) are no longer of interest to NGS, so do not report them. Good condition for professional purposes means that the POSITION hasn't been compromised. They don't care a lot about the cosmetics of the mark. A disk that has been hammered on by vandals can be GOOD if they can set their pole on the exact same location and height that was originally measured. The most pristine looking disk in a post that is seriously leaning is at best POOR and perhaps DESTROYED. You will be asked when using the NGS entry form whether the location is suitable for GPS. You can select "Don't Know" and that's fine. The criteria for professional GPS are generally clear sky view except for minor items like a pole or small tree. They are interested in visibility from 15 degrees above the horizon up. If you extend your arm, spread your hand, and set the little finger on the horizon, your thumb will be close enough to 15 degrees.

I'm not sure where one would find a United States Geological Survey data sheet. You probably found a data sheet on the National Geodetic Survey (NGS) site for a US Coast and Geodetic Survey (US C&GS) mark (the predecessor name for NGS). There was a thread with pictures long ago on this forum about a recovery of Buttermilk. Buttermilk, of course, was a geodetic mark as opposed to the M&D cadastral (land boundary) stones.

In doing the experiment described in a related post, I've tried to sort through the various datums, datum tags, and other mysterious designations on the data sheets. This is more detailed information than most forum posters get into, so I thought I'd summarize what I think I know about datum realizations. Correct me where I'm wrong. Some of this summary comes from: http://geodesyattamucc.pbworks.com/f/25Feb2010_NAD.pdf http://www.plso.org/Resources/Documents/Dave%20Doyle%20PLSO%202014%20HISTORY%20OF%20GEODETIC%20DATUMS.pdf You may also want to read articles such as: http://www.ngs.noaa.gov/PUBS_LIB/develop_NSRS.html http://www2.arnes.si/~gljsentvid10/datm_faq.html http://www.ngs.noaa.gov/INFO/OnePagers/NewDatumsOnePager.pdf http://www.ngs.noaa.gov/faq.shtml http://help.arcgis.com/En/Arcgisdesktop/10.0/Help/index.html#//003r00000009000000 Following regional triangulations begun by Hassler, the US Coast & Geodetic Survey worked through the 1800's and connected across the continent and formed the US Standard Datum. Adjustment of the data collected into the early 20th century resulted in the US Standard Datum in 1901 and then an update to the North American Datum of 1927 (NAD27). These used the Clarke ellipsoid model of the earth and were defined relative to Meades Ranch. NAD27 had a network accuracy of about 10 meters and local accuracy of 1:100,000. After several decades of use and the gathering of more data (including pre-GPS satellite doppler data and VLBI vectors), a new datum was defined. It used the internationally adopted GRS80 ellipsoid earth model that fits the whole world better than Clarke and (with minor differences) is essentially the earth model used for GPS. It was defined as the North American Datum of 1983 and became available in 1986, hence NAD83(86). This realization had a network accuracy of about 1 meter and local accuracy relative to nearby stations of 1:100,000. That would be 2 arc seconds or 1 foot in 19 miles at 95% confidence. The topographic maps of the country were prepared in NAD27 coordinates. You will find that even a recreational GPS can see the difference between that and NAD(83); in my area it is about 50 feet so you need to account for it when using topo map with GPS. GPS operates with a datum that is used internationally, IGS08 which is for most purposes the same as the International Terrestrial Reference Frame (ITRF2008). The US military calls their version WGS84 and update it to match the international datum every several years with a datum tag of the GPS week, like (G1674). NGS chose to fix NAD83 to the North American tectonic plate to minimize coordinate changes. The two datums drift apart by a couple centimeters per year. Additionally, it was learned that the initial realizations of those two datums were not as close as hoped, so the difference is more like a couple meters. Most recreational GPS units ignore the difference. For precise work the NGS horizontal time-dependent positioning program (HTDP) provides good estimates of the conversion at a given time epoch. Since then additional GPS data has been used to improve the NAD83 realization. State-by-state updates were done in the 1990's under the name High Precision GPS Network (HPGN), renamed High Accuracy Reference Network (HARN) which you see on signs as you recover some stations. Some states had two versions, so the latest in any state is called the Federal Base Network (FBN), a label you see on data sheets. You also see Cooperative Base Network (CBN), which is a densification of the high accuracy stations. The 199x FBN adjustments updated all horizontal control stations in the data base using additional VLBI, CORS, and other GPS measurements. Successive adjustments held the highest precision stations (VLBI and CORS) and adjusted other GPS stations to them, and then adjusted stations with no GPS data. Only a minority of the old tri-stations had HARN GPS data. Additional HARN stations resulted from GPS measurements on elevation bench marks that had no prior accurate lat-lon. The FBN stations improved accuracy by a factor of at least 10 relative to NAD83(86) but the tri-stations that were not occupied by GPS improved less. HARN/FBN was still NAD83 because it used the same definitions, but the realization was different because it used additional measurements that shifted things a bit, hence names like NAD83(1995). I think of realizations like a fish net. After you tie down the lat-lon of some points on the net, there is still some sag or wandering by the rest of the net. Each realization gets its points better aligned, but not all points have equally good data. NGS created NAD83(CORS96) which included only CORS stations and had an accuracy of about a centimeter. The next realization (update) was NAD83(2007) with the goal to remove inconsistencies between the state adjustments and with CORS. It held fixed the NAD83(CORS96) positions. This time only GPS data was used, so triangulation stations that didn't have GPS data were omitted, and you still see their NAD83(199x) coordinates at the top of their data sheets. Those old coordinates typically have a fraction of a foot to even a few feet of local warpage relative to the stations with GPS data, which is not modeled because it is random error in the old measurements. Intersection stations are going to be less accurate than triangulation stations. The latest is NAD83(2011, epoch 2010.0), which you see on data sheets having good GPS data. If a project design is based on an older realization, then measurements tied to the adjusted monuments can be converted accurately enough to 2007 and FBN, but stations that were not occupied with GPS will usually not match well. (corrections welcome)

You may want to read the related post about datum realizations to help this make more sense. I have a project that I've worked with occasionally over several years to play with measurements, and get a better understanding of the C&GS triangulations. I observe angles to tall objects such as the red lights on radio towers, serving as intersection stations. I have a few points with known coordinates as a basis and do least squares fitting of the measurements to estimate coordinates for everything. A church spire NJ0770 didn't seem to fit very well when I used the latest data sheet NAD83(96) coordinates and converting to NAD83(2011) with GEOCON didn't help much. Then last fall I acquired an "antique" professional GPS, a Trimble 4000sst. Anybody who used one when they came out in the early 1990's would consider them junk today because they only process L1 and sort of process L2, but no P code. Newer receivers process all of those signals. I figured out how to manipulate the data files so the NGS OPUS service would process them and return NAD83(2011) coordinates. I got a couple OPUS sessions on the ground near the church and did triangulation to tie in the spire, and find it to be about 1.6 foot east of where the data sheet plus GEOCON would put it, and much closer to my older measurements. So I went to first-order triangulation station NJ0775 a few miles away, dug down to the disk, and got a 4-hour GPS session that came up 1.0 ft mostly east from the 96+GEOCON coordinates. The nearest tri-station NJ0769 is deep in someone's yard and doesn't have enough sky anyway. Its RM3 is also somewhat obscured and gave me a file that was so weak in L2 OPUS wouldn't give useful results. I got someone to run the L1-only portion of the data and it came back 1.0 ft mostly east of prediction. My conclusion is that the old triangulation network in this area was very good in relation between nearby tri-stations, and good to about a foot with respect to stations that are tens of miles away, but the intersection stations (church spire) can be off more than that even with respect to nearer triangulation stations. The triangulation network had some warpage in this area for stations without GPS data, relative to the stations used in the '96 adjustmen,t because the nearest stations with both triangulation and GPS data are tens of miles away. That is well within the goals of the old triangulations. This has been an interesting and educational exercise. I'd like to eventually check more tri-stations around here to better characterize the shift. (Corrections welcome)

The topic comes up occasionally about careless logging by people who don't check the stamping to see they have the right disk. One of my first few NGS logs turned out to be WRONG despite having the right agency and stamping. I guess the lesson is that you need to understand civil engineering terminology to be sure something hasn't been rebuilt. I thought the road had just been raised over the old bridge but it seems this is a new culvert, with a new disk that somebody in their questionable wisdom decided should have the same stamping. NJ0584 STATION RECOVERY (2014) NJ0584 NJ0584'RECOVERY NOTE BY NATIONAL GEODETIC SURVEY 2014 NJ0584'THIS REPORT WAS SUBMITTED BY STEVEN MILLIGAN. THERE IS STILL A NJ0584'MONUMENT WITH A DISK STAMPED LINN CO ENG DEPT 1402, BUT IT IS NOT NJ0584'IN THE SAME STRUCTURE AS DESCRIBED IN THE 1934. IN 1934, THE DISK NJ0584'WAS IN THE TOP OF THE CENTER OF THE SOUTH CONCRETE GUARD RAIL OF A NJ0584'TWIN 5 BY 12 FOOT HIGHWAY BRIDGE, AND NOW IT IS IN THE CENTER OF NJ0584'THE TOP OF THE SOUTH HEADWALL OF A TWIN 6 BY 12 FOOT RCB. A +2.75 NJ0584'HOUR OPUS SESSION SHOWS A DIFFERENCE FROM THE PUBLISHED NJ0584'ORTHOMETRIC HEIGHT OF THE DISK OF -1.013 METER. I CONTACTED LINN NJ0584'COUNTY AND FOUND THAT THE ROAD WAS RELOCATED IN 1968, AND THE NJ0584'BRIDGE WAS REPLACED BY A CULVERT. ALSO, LINN COUNTY SHOWS TWO BM'S NJ0584'WITH A DISK STAMPED 1402 WITH A ORTHOMETRIC DIFFERENCE OF -3.15 NJ0584'FEET.THE 2004 GEOCACHER DID NOT FIND THE 1934 DISK, BUT INSTEAD NJ0584'FOUND THE POST 1968 DISK.

The disk you saw was probably never entered in the NGS data base. Only a small fraction of the disks out there in the country were ever measured to the standards needed and submitted for inclusion in the NGS list, even though those disks serve a useful purpose for someone. The Geocaching list of bench marks is a snapshot of the NGS list from about 2001, which is long enough after 1988 that it should have been there if the data was submitted at the time the disk was placed. We don't expect the Geocaching list of marks to ever change. Nothing is deleted, and nothing is added to keep up with NGS. Once a disk is entered at NGS, it stays in their list, although if it is reported destroyed you have to use a different search to bring it up there.