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# Accuracy of locations for triangulation stations

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Or - How big a hole to dig?

I have occasionally searched for "lost" triangulation stations by computing the distance from a nearby known station. We did this for two Mount Tom stations several weeks ago. The known station was MZ1808 MOUNT TOM which is a first order station and MZ1807 MOUNT TOM BORDEN which is a third order station and was "lost".

Using the NGS "Inverse" program I calculated a distance of 3.3908m (11.12 feet) between the stations. We dug there using that distance and the azimuth and since this was 18 inches underground and we were using small tools, we could not at first find it. Then we noticed in an old recovery log the distance was measured as 3.5195m (11.54 feet), a difference of about 5 inches. We extended our hole 5 inches in the appropriate direction and found the mark. Horray!

My assumption is that the location of the known first order station (MZ1808) was more accurate, and the discrepancy was mostly due to the uncertainty of the third order station (MZ1807), but I'm at a loss to find any way to put numbers on this uncertainty. I've seen accuracy estimates for this type of (pre-GPS) stations, but always as a fraction of the distance and azimuth from other stations, but what other stations? How do I turn this fraction into an uncertainty of the location as in +/- so many cm?

A reason this is important to me is that there is another situation where I want to find a lost station, given a known station. In this case both stations are first order, so I'm ahead of where we were on Mount Tom. In the new case the known station is MY3799 UNKONOONUC 2 and the lost one is MY3800 UNKONOONUC 1848. The calculated distance is 5.7415m (18.83 feet). In this case there is no old recovery log with a measurement to help me. There is a distance from a USGS tablet given in 1932, but I have no location information data for that tablet, and it might be gone anyway. Besides the surveyor who measured that in 1932 (before the newer station was established) wasn't sure he found the old lost station anyway.

So how big a hole do I dig (mark is supposed to be 8 - 10 inches underground) .

In an old publication (CGS Special Publication 76) This problem is adressed:

In many cases the enginer fails to rocover a station which still exists. This failure may be due to changes in the surrounding topography or to the destruction of the surface or reference marks, while the underground mark may still remain in place. By digging in the proper place the mark could probably be recovered, but without the guidance of the reference marks or of the local topography the station can be recovered only by locating a new point in the immediate vicinity of the old point from the nearest available triangulation. The geographic position of the new station can be compared with that of the old station, the linear relation of the two stations can be determined, and then an offset can be measured to the place indicated by the comparison as the probable location of the old station
Why, that's just what I'd like to do, but as above I ask: how big a hole?

To summarize:

1) Is the 3.5195m vs 3.3908m difference what you'd expect (statistically) for the Mount Tom case, or was it just the luck of the draw?

2) What might I expect for the Unkonoonuc case?

3) When stations are upgraded with GPS, what kind of change in the location from the pre-GPS location is usually found for first order stations.

Edited by Papa-Bear-NYC

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The reason for the discrepancy in the distance is that the distance of 3.5195m mentioned in the 1896 description for Mt Tom Borden was never carried over to the observation file that the field unit submitted. Therefore it was never coded and used in the adjustment of the positional relationship between these two stations. Since distances are usually stronger than angle observations if this measurement had been in the observation log it would have been coded with a very low standard deviation and would therefore have been held virtually fixed in the NAD 83 adjustment. Since it wasn't there the positions for the two points were determined independently by the triangulation measurements relative to the network

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This is where I would use my Stainless steel rod with a T handle.

Or probe as I call it.

It is about 36 inches long and 1/4 inch thick with a rounded...not sharp point.

Once ground has been disturbed it is never as hard as the surrounding ground.

We have also used this for many other probing purposes as Old bottles,graves,Artifacts and the likes.

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Pappa Bear,

You spurred me into completing two recoveries that square nail and I completed 2 weeks ago, both are relevant to your questions.

The attached USGS Triangulation book was found in 2007 and a return to this station was required to find the buried bottle RM's.

NGS did not call out the bottle RM's and so we did not look for them in 2005, but we talked about going back there when the ground thawed out and seeing if we could find what they had buried.

USGS Station Coulee

On May 3, 2008 we decided to head out early for a short and quick 575 mile round trip journey to see if we could find these 104 year old bottles.

We arrived at the mark at 9:45 in the morning and it was clear and warming to around 55 degrees. Square Nail set up his staff compass over the mark and turned in the 174 degree RM Azimuth and there was a flat stone on the surface at that point, I moved the stone and proceeded to gently dig in about a 2 foot radius. Square Nail then turned the 358 degree Azimuth and measured out to find another flat stone at that point. He took photos while I was digging. I was down at least 12 inches in the 2 foot radius; did they really bury a bottle, did they blow an angle or distance, why am I not hitting anything - the RM was to be buried 8 inches? I stopped and we went to the other RM position and started digging down, the digging was fairly easy with a sandy-silty soil. After about 10 or 15 minutes of digging I hit a shiny object and sure enough at about 10" below the surface the top of a bottle began to emerge. It had a cork in it and was buried stem upright, it appears to be a beer or whiskey bottle and is in good condition with an old chip out of the lip, but otherwise intact. There must me a bottle under that other rock, so back to work on the other RM, I expanded the hole and kept digging down. Finally I spotted some shine on the northwest edge of our hole and approximately 20" below the surface. A Carters Full Quart bottle in excellent condition appeared from the depths. It was more than twice as deep as called for and appeared to be approximately 5 degrees out in the Azimuth. In the area we also found a couple odd sized rim fire casings and an old rusted shovel head, the shovel probably being from the USGS crew.

So first, they were called for buried 8" - we did not know if they were upright or upside-down, the bottom buried 8" with the tops protruding and probably broken. When we found them one at approximately 10" and the other 20" below the surface. Don't assume that they are as stated for depth. These both fit right on for the RM distances and the south RM was nearly perfect for angle, but the northerly RM was much deeper and approximately 5 degrees out. Remember that these were very short distances, so the angular calls were not that significant for the amount that they were off.

We made another stop on our way home for one last look for an 1889 Missouri River Commission station that we had each separately and jointly searched for two times in the past 5 years. We had a new probe and decided that we could find the sub-surface mark.

Missouri River Commission Station BENTON - 1889

SS1660 ***********************************************************************

SS1660 DESIGNATION - BENTON

SS1660 PID - SS1660

SS1660 STATE/COUNTY- MT/CHOUTEAU

SS1660 USGS QUAD - FORT BENTON (1954)

SS1660

SS1660 *CURRENT SURVEY CONTROL

SS1660 ___________________________________________________________________

SS1660* NAD 83(1992)- 47 48 49.20167(N) 110 42 06.47935(W) ADJUSTED

SS1660* NAVD 88 - 902.5 (meters) 2961. (feet) VERTCON

SS1660 ___________________________________________________________________

SS1660 LAPLACE CORR- -0.50 (seconds) DEFLEC99

SS1660 GEOID HEIGHT- -14.69 (meters) GEOID99

SS1660

SS1660 HORZ ORDER - THIRD

SS1660

SS1660.The horizontal coordinates were established by classical geodetic methods

SS1660.and adjusted by the National Geodetic Survey in July 1992.

SS1660

SS1660.The NAVD 88 height was computed by applying the VERTCON shift value to

SS1660.the NGVD 29 height (displayed under SUPERSEDED SURVEY CONTROL.)

SS1660

SS1660.The Laplace correction was computed from DEFLEC99 derived deflections.

SS1660

SS1660.The geoid height was determined by GEOID99.

SS1660

SS1660; North East Units Scale Converg.

SS1660;SPC MT - 396,678.031 510,042.177 MT 0.99949051 -0 52 44.8

SS1660;UTM 12 - 5,295,633.484 522,324.366 MT 0.99960612 +0 13 15.4

SS1660

SS1660 SUPERSEDED SURVEY CONTROL

SS1660

SS1660 NAD 83(1986)- 47 48 49.19803(N) 110 42 06.45806(W) AD( ) 3

SS1660 NGVD 29 - 901.7 (m) 2958. (f) VERT ANG

SS1660

SS1660.Superseded values are not recommended for survey control.

SS1660.NGS no longer adjusts projects to the NAD 27 or NGVD 29 datums.

SS1660.See file dsdata.txt to determine how the superseded data were derived.

SS1660

SS1660_MARKER: DS = TRIANGULATION STATION DISK

SS1660_SETTING: 17 = SET INTO TOP OF METAL PIPE DRIVEN INTO GROUND

SS1660_STABILITY: D = MARK OF QUESTIONABLE OR UNKNOWN STABILITY

SS1660

SS1660 HISTORY - Date Condition Recov. By

SS1660 HISTORY - 1889 MONUMENTED MORC

SS1660 HISTORY - 1954 MARK NOT FOUND USGS

SS1660

SS1660 STATION DESCRIPTION

SS1660

SS1660''DESCRIBED BY US GEOLOGICAL SURVEY 1954

SS1660''FOLLOWING DESCRIPTION BY MORC

SS1660''

SS1660''BENTON IS ON THE LEFT BANK, ON THE HIGHEST PART OF BENTON HILL, 2 MI.

SS1660''W. FROM FORT BENTON, AND NEAR THE HELENA ROAD.

SS1660''

SS1660''NOTE--REPORTED NOT FOUND BY USGS IN 1954.

SS1660''

SS1660''STATION MARK--STANDARD MONUMENT WITH AN IRON PIPE AND CAP.

As you can see USGS did not find it in 1954 and the USC&GS set a new station nearby in 1949

SS1568 ***********************************************************************

SS1568 DESIGNATION - FORT BENTON

SS1568 PID - SS1568

SS1568 STATE/COUNTY- MT/CHOUTEAU

SS1568 USGS QUAD - FORT BENTON (1954)

SS1568

SS1568 *CURRENT SURVEY CONTROL

SS1568 ___________________________________________________________________

SS1568* NAD 83(1992)- 47 48 49.37880(N) 110 42 06.35948(W) ADJUSTED

SS1568* NAVD 88 - 902.53 (+/-2cm) 2961.1 (feet) VERTCON

SS1568 ___________________________________________________________________

SS1568 LAPLACE CORR- -0.50 (seconds) DEFLEC99

SS1568 GEOID HEIGHT- -14.69 (meters) GEOID99

SS1568

SS1568 HORZ ORDER - SECOND

SS1568 VERT ORDER - THIRD ? (See Below)

SS1568

SS1568.The horizontal coordinates were established by classical geodetic methods

SS1568.and adjusted by the National Geodetic Survey in July 1992.

SS1568

SS1568.The NAVD 88 height was computed by applying the VERTCON shift value to

SS1568.the NGVD 29 height (displayed under SUPERSEDED SURVEY CONTROL.)

SS1568.The vertical order pertains to the superseded datum.

SS1568

SS1568.The Laplace correction was computed from DEFLEC99 derived deflections.

SS1568

SS1568.The geoid height was determined by GEOID99.

SS1568

SS1568; North East Units Scale Converg.

SS1568;SPC MT - 396,683.460 510,044.753 MT 0.99949052 -0 52 44.8

SS1568;UTM 12 - 5,295,638.962 522,326.837 MT 0.99960613 +0 13 15.5

SS1568

SS1568: Primary Azimuth Mark Grid Az

SS1568:SPC MT - FORT BENTON AZ MK 314 37 52.1

SS1568:UTM 12 - FORT BENTON AZ MK 313 31 51.8

SS1568

SS1568|---------------------------------------------------------------------|

SS1568| PID Reference Object Distance Geod. Az |

SS1568| dddmmss.s |

SS1568| FORT BENTON RM 2 6.413 METERS 01106 |

SS1568| SS1527 HIGHWOOD BALDY APPROX.41.7 KM 1723810.1 |

SS1568| FORT BENTON RM 1 7.690 METERS 27507 |

SS1568| FORT BENTON AZ MK 3134507.3 |

SS1568|---------------------------------------------------------------------|

SS1568

SS1568 SUPERSEDED SURVEY CONTROL

SS1568

SS1568 NAD 83(1986)- 47 48 49.37514(N) 110 42 06.33809(W) AD( ) 2

SS1568 NAD 27 - 47 48 49.48600(N) 110 42 03.56100(W) AD( ) 2

SS1568 NGVD 29 - 901.68 (m) 2958.3 (f) LEVELING 3

SS1568

SS1568.Superseded values are not recommended for survey control.

SS1568.NGS no longer adjusts projects to the NAD 27 or NGVD 29 datums.

SS1568.See file dsdata.txt to determine how the superseded data were derived.

SS1568

SS1568_MARKER: DS = TRIANGULATION STATION DISK

SS1568_SETTING: 7 = SET IN TOP OF CONCRETE MONUMENT

SS1568

SS1568 HISTORY - Date Condition Recov. By

SS1568 HISTORY - 1949 MONUMENTED CGS

SS1568

SS1568 STATION DESCRIPTION

SS1568

SS1568''DESCRIBED BY COAST AND GEODETIC SURVEY 1949 (MJT)

SS1568''STATION IS ABOUT 2 MILES WEST OF FORT BENTON, ON THE HIGHEST

SS1568''POINT BETWEEN THE RIVER AND THE INTERSECTION OF U.S. HIGHWAY 87

SS1568''AND THE ROAD LEADING INTO FORT BENTON, ABOUT 300 YARDS NORTH

SS1568''OF THE RIVER, 12 FEET NORTHWEST OF A WITNESS POST.

SS1568''

SS1568''TO REACH FROM THE POST OFFICE IN FORT BENTON, GO NORTH FOR 0.3

SS1568''MILE TO A T-INTERSECTION, TURN LEFT AND GO WEST FOR 1.65 MILES

SS1568''TO TOP OF HILL AND THE JUNCTION WITH U.S. HIGHWAY 87 AND A TRACK

SS1568''ROAD ON THE LEFT, TURN LEFT ON TRACK ROAD FOR ABOUT 20 YARDS

SS1568''TO THE AZIMUTH MARK ON THE RIGHT, CONTINUE SOUTH AND SOUTHEAST

SS1568''FOR 0.35 MILE TO THE TOP OF THE HILL AND THE STATION.

SS1568''

SS1568''REFERENCE MARK NO. 1 PROJECTS 4 INCHES AND THE DISK IS STAMPED

SS1568''FORT BENTON NO 1 1949.

SS1568''

SS1568''REFERENCE MARK NO. 2 PROJECTS 6 INCHES AND THE DISK IS STAMPED

SS1568''FORT BENTON NO 2 1949.

SS1568''

SS1568''AZIMUTH MARK IS APPROXIMATELY 0.3 MILE NORTHWEST OF THE STATION,

SS1568''69 FEET SOUTH OF THE APPROXIMATE CENTER OF U.S. HIGHWAY 87

SS1568''AND 2.5 FEET EAST OF A SECTION LINE POST. THE MARK PROJECTS

SS1568''6 INCHES AND THE DISK IS STAMPED FORT BENTON 1949.

SS1568''

SS1568''ALL MARKS ARE STANDARD DISKS SET IN THE TOPS OF 12-INCH SQUARE

SS1568''CONCRETE POSTS.

SS1568''

SS1568''A 4-FOOT STAND AT FORT BENTON WILL SEE 4-FOOT STANDS AT TETON

SS1568''(MO. R C), SKIT AND BENTON.

We had located this CGS station after a couple visits over 4 years using a metal detector and found it buried about 6 inches. I did a geodetic inverse between the two stations and came up with approximately 19.63' @ 204.4 degrees Azimuth. We stopped at this site on ourway back home and set up the compass pulled the 19.63' and used a 4' probe to check the area. After about a dozen different probes I hit a good sounding clink about 2 feet down; after a few minutes of furious digging, we have success! We found a beautiful stone 18"x18"X4" with a drill hole approximately 1" deep and a triangle above and US below. Station Benton does exist! We took photos pushed some wire in the drill hole and drove a rebar on the north edge of the stone for future recovery. We had a pipe with us, but the stone is only 1 1/2 - 2 feet deep and we had a four foot pipe. This is now findable and I will submit a recovery, so the pipe is really un-needed. I am sure that the old pipe and cap were sticking out of the ground by a few feet in this very silty loose soil and was pitched into the Missouri River years ago. From the photos you can see that the pipe mark is very faint, which tells me that it has been gone for a long time. We know it was gone in 1949. Before we left the site a pickup pulled up and the landowner came up to see what we were doing and was concerned about fire in his field. He was very nice and when we told him what we were doing he said he would like to see the mark. We gladly went back and dug it up and explained to him the significance and history of the mark. He was in awe of the mark, but what he finally said was; "you drove over from Missoula to find a buried stone? If I grabbed my shovel and told my wife I was heading to Missoula to dig up a stone she would think I was Nuts. So you guys must be Nuts, but that is really neat what you found."We also found an old shell casing in the dirt above the monument at this site as well as the earlier site.

We did find the mark at the azimuth and very near the inverse distance between a second order and third order station. I do not believe that you will find a distinct difference between different order stations and that they would be more of a random difference around an ellipse.

Did not really answer your questions, but I did want to show how we had used your same theories and did have success using them.

CallawayMT

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Callaway

Fantastic recoveries!

What did you do with the bottles? My ethical side would say "Rebury them". My human side would say, "Put them on the coffee table, no one will look for them for another 100 years"

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Callaway

Fantastic recoveries!

What did you do with the bottles? My ethical side would say "Rebury them". My human side would say, "Put them on the coffee table, no one will look for them for another 100 years"

I was going to mention that and did forget. We did keep these two bottles, but replaced them with rebar. The rebar are actually findable without finding the mark first and I will file a report with NGS. As you can see from the post, unless you had found the original USGS reports, you would never even know that the bottles existed.

There would be no possible way of ever finding the bottles without knowing where the station existed. I do not abdicate plundering these old stations, but in my opinion we did leave it better than we found it and will not take any further bottles if and when we go see what was buried at the other approximate 15 stations in the report.

CallawayMT

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Did you put your land surveyor plastic cap on the rebar? Did you put the rebar where the bottle was or where the RM measurement indicated?

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Did you put your land surveyor plastic cap on the rebar? Did you put the rebar where the bottle was or where the RM measurement indicated?

Yes the rebar are where the bottles were and no I did not put my LS numbered cap on the rebar as it is not required or necessary in this case.

I think this can or will make for an interesting conversation. Do you feel that we did wrong by taking the bottles?

CallawayMT

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No, I don't think taking a bottle apiece is wrong. It is unlikely any one else would find them, or appreciate them in the same way if they did. In a sense they would probably go to waste if left. They don't have much archaeological value; the fact that those bottles were used in that area at that time is probably already well known. The fact that you preserved the locations counts in your favor.

If you went around taking all the bottles from a set of marks, then it would start to look greedy and would be more debatable. You would be seriously reducing the possibilities that someone else might be able to enjoy a similar find.

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Did you put your land surveyor plastic cap on the rebar? Did you put the rebar where the bottle was or where the RM measurement indicated?

Yes the rebar are where the bottles were and no I did not put my LS numbered cap on the rebar as it is not required or necessary in this case.

I think this can or will make for an interesting conversation. Do you feel that we did wrong by taking the bottles?

CallawayMT

Having 'reclaimed' a few marks myself, I can understand the temptation.

I don't know how I would have acted in the situation described...in the heat of the moment, as it were.

I would like to think I would have stopped digging when I determined that I had indeed found my objective in good condition.

Only time will tell if the rebar is a preferable substitute for the glass bottles. Steel rebar is magnetic, and much more easily detectable (until someone invents a glass detector). Unfortunately, steel will eventually corrode away. The glass bottles, however, would likely remain unchanged for milennia...or until some geologic force completely destroyed the site.

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I have been second guessing our acquisition and may still replace the bottles at some point in the future. I do give talks on survey history and thought that they may come in handy for a talk some day.

I did not consider the taking of the bottles as any sort of degradation to the survey or monument or I would have never considered taking them. To put things into survey perspective; I have explained in the past that intersection stations have about a 0.05% chance for being used as a survey monument in this age of time. These old second and third order triangulation stations for all practicallity are also not very usable. They can be used for conventional stations to put a very low order geodetic or state plane value on nearby objects, but they will not be used for a GPS base station without putting an updated value on the position. If I were to set a GPS base on this station for instance and then send the GPS data into NGS for an OPUS position I would not expect it to be any closer than about 3 feet in value.

That being said, I do use any and all existing survey monuments in a project area if it is convenient to use for a base station. You have a solid highly visible monument that is easy to describe and already has a data sheet assigned to it.

These types of stations are my favorite to go find for their historical value and for the appreciation of the work that took place to monument and survey this mark. This station has not been changed and the RM bottles had been excluded by the USC&GS and NGS, but we were able to find them based on the station. If the surveyors had blown and angle by more than 10 degrees or a distance by more than a foot, we would have never found them. If this station were lost, the RM's would never be used to reestablish the station due to the low value that it holds. Does any of this make it right that we took the bottles? Maybe not.

CallawayMT

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Does any of this make it right that we took the bottles? Maybe not.

CallawayMT

That is like asking "Is it wrong to take a disk that has been dislodged from it's setting?"

If it has no value (considering the time and effort it took to recover the unbroken bottles) since their location was in question and the quality of the settings was below the threshold for a quality station there has been minimal impact on that benchmark. Would very many surveyors have spent the time and energy needed to locate the bottles and then use them for a job? Or is there more value in using them now for teaching and lecturing on old survey practices?

Is replacing the bottles with rebar any different than enlarging an RM's drill hole and inserting a new disk?

John

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...

We made another stop on our way home for one last look for an 1889 Missouri River Commission station that we had each separately and jointly searched for two times in the past 5 years. We had a new probe and decided that we could find the sub-surface mark.

Missouri River Commission Station BENTON - 1889

...

We had located this CGS station after a couple visits over 4 years using a metal detector and found it buried about 6 inches. I did a geodetic inverse between the two stations and came up with approximately 19.63' @ 204.4 degrees Azimuth. We stopped at this site on ourway back home and set up the compass pulled the 19.63' and used a 4' probe to check the area. After about a dozen different probes I hit a good sounding clink about 2 feet down; after a few minutes of furious digging, we have success! We found a beautiful stone 18"x18"X4" with a drill hole approximately 1" deep and a triangle above and US below. Station Benton does exist!

...

We did find the mark at the azimuth and very near the inverse distance between a second order and third order station. I do not believe that you will find a distinct difference between different order stations and that they would be more of a random difference around an ellipse.

...

CallawayMT

Two questions:

1) how close was the distance for Benton? (did you remeasure it after you dug it up?)

2) What type of compass was your friend using with the tripod? How accurate? Is this consumer grade or professional equipment - in other words could I afford one ?

And I think it was fine to keep those bottles. Just leave that stone where it was!

Thanks

Richard aka Papa Bear

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Richard,

Here is a link to the compass and tripod attachment that we used at Benton and Coulee. You can get the compass in two different configurations. I would suggest the quad as it is easier to use in most situations. I have retraced mining claim boundary lines and even section lines and find the accuracy as good as the effort I am willing to apply. Some times only a foot or two off in 1500 feet.

http://www.brasscompass.com/brunton.htm

square nail

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My opinion is that the bottles should be replaced in their original positions. At first I thought they were just some junk put above a station, but after reading the original station notes, I saw that these 2 bottles are the reference marks. They should've been left standing as in this picture, without any further digging.

A very important aspect of benchmark hunting and our role in recovery reports is that we're taking only pictures.

I collect another type of bottle (not ink and beer bottles like these) and can say that the ink bottle and beer bottle are not worth much at all; maybe \$5 each or less. The point being that the historic aspect and positions of these bottles is far more valuable than the bottles themselves, just like the actual value of any brass disk.

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It appears that CallawayMT & square nail made the grave mistake of failing to mention that they were professional surveyors and not just amateur GC.com recoverers.

The pros have a certain latitude when it comes to 'upgrading' a survey mark to improve its use. We amateur just report on the condition of a station.

John

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Richard,

Here is a link to the compass and tripod attachment that we used at Benton and Coulee. You can get the compass in two different configurations. I would suggest the quad as it is easier to use in most situations. I have retraced mining claim boundary lines and even section lines and find the accuracy as good as the effort I am willing to apply. Some times only a foot or two off in 1500 feet.

http://www.brasscompass.com/brunton.htm

square nail

WOW! That is one nice piece of equipment!

I did find them for sale on EBay for much less (~\$250).

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Look at any ebay listing VERY carefully. This item may be among those that are popular to copy and sell for less, and the copies won't have the precision of the original.

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My opinion is that the bottles should be replaced in their original positions. At first I thought they were just some junk put above a station, but after reading the original station notes, I saw that these 2 bottles are the reference marks. They should've been left standing as in this picture, without any further digging.

A very important aspect of benchmark hunting and our role in recovery reports is that we're taking only pictures.

I collect another type of bottle (not ink and beer bottles like these) and can say that the ink bottle and beer bottle are not worth much at all; maybe \$5 each or less. The point being that the historic aspect and positions of these bottles is far more valuable than the bottles themselves, just like the actual value of any brass disk.

BDT,

You are correct in what you say about geocachers and benchmarking and as John posts, I am a Professional Land Surveyor, Square Nail is not. For that reason I accept any responsibility as to our actions when we are together.

These bottles have no monetary value what so ever to me, they only have historical value. Why did NGS choose not to include the RM's when they brought these marks into the data base? I do not know, I do know that this station, after I submit a recovery, will have an increased chance for recovery if it is lost. BUT it would never be recovered if lost for any survey efforts. It does have a historical value and yes, we did degrade that. Would anybody ever come looking again in the future? Who knows.

As a surveyor I do not feel that we did anything improper, or obviously I would not go tooting my horn about it. As a historian I do feel that we should be putting the bottles back in place. Also as a surveyor I should be setting an example in this forum, if what I did causes somebody else to go out and dig up survey monuments or control, then I have performed a dis-service. This is why I opened myself up to scrutiny amongst those that frequent this forum. I feel that the majority of you who post here on a regular basis act very professionally in the recoveries and reports that you submit, I value your opinions and I feel the opinions of others sometimes helps us right our personal and ethical compasses.

Thanks for your input,

Kurt aka CallawayMT

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My thoughts:

1) Leave the station as good or better than you found it.

2) As non-professionals, we BM hunters can only take pictures and maybe clean things up a bit (as discussed in previous threads).

3) Professional surveyors have much more capability than non-professionals, and can do what is proper within their profession. They know.

I was a little "concerned" myself until I remembered Kurt was a professional, then I thought "OK, sure, better now".

One hypothetical question for Kurt, if you don't mind: If a bottle had BEEN the station / mark, and not undocumented reference marks, would have done things differently? What?

Klemmer

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CallawayMT -

I sometimes forget who is and who is not a professional surveyor in these forums.

This information does set quite a different slant on the whole thing, I think. Certainly a professional can properly evaluate what to do about a situation such as these non-metal reference marks.

I think it's a good thing to clarify here in this topic the difference between what professional surveyors do versus what us amateur benchmark hunters should and should not do.

I did want to get across the idea that old bottles like these are not treasures to obtain for their own value. At an antique bottle show (I've been to several) bottles like these are generally found in the "\$2 box".

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My thoughts:

1) Leave the station as good or better than you found it.

2) As non-professionals, we BM hunters can only take pictures and maybe clean things up a bit (as discussed in previous threads).

3) Professional surveyors have much more capability than non-professionals, and can do what is proper within their profession. They know.

I was a little "concerned" myself until I remembered Kurt was a professional, then I thought "OK, sure, better now".

One hypothetical question for Kurt, if you don't mind: If a bottle had BEEN the station / mark, and not undocumented reference marks, would have done things differently? What?

Klemmer

Absolutely I would have done differently. If a bottle were the station, I would not disturb in the least, unless I am willing to take the time and effort to go throught the NGS blue-booking process, I would never disturb an un-disturbed station of any sort.

I did not de-grade this station in any way, these were RM's and the station still has reference marks of a more findable and useable value.

Thanks,

Kurt

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...

CallawayMT

Two questions:

1) how close was the distance for Benton? (did you remeasure it after you dug it up?)

2) What type of compass was your friend using with the tripod? How accurate? Is this consumer grade or professional equipment - in other words could I afford one ?

And I think it was fine to keep those bottles. Just leave that stone where it was!

Thanks

Richard aka Papa Bear

Richard,

Unfortunately, we did not remeasure after we found the sub-surface mark. I want to keep this a fun hobby for me and as such, I do not do as good of work as many of you at documenting these discoveries. It was within a degree for angle and my guess is that it was within a foot(probably a couple tenths) for distance.

With these type of compasses on a tripod and a proper declination inserted, I would say they are accurate to within a degree maybe two. Absolutely a useful tool for these types of recoveries.

Kurt

As a sidenote, I was asked by Wintertime why I don't use my name in this forum, I have always just used the geocaching name that I had signed up for years ago and never really thought about it. I have had emails from more than a few people in this forum and have always used my name in those emails. If you want to know a little about me, you can go to this link Caching Now Story and see the article that Berntsen asked me to write a few months back.

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I wanted to make an update to my earlier posts. The following NGS recovery was submitted:

This station falls on a high bluff of BLM land approximately 4.5 miles due north from the town of Big Sandy. From the town of Big Sandy travel northerly 2.5 miles along state highway 87 to a gravel road on the left, travel north on this gravel road for 4 miles, near a large gravel pit, turn left(west) and travel 1 mile to a 4-way intersection and turn left(south) for 1.4 miles and a wire gate on the left, go through the gate and up the west facing bluff for 1000 feet and the station at the top of the bluff.

A standard 3 3/4" USGS brass cap on an iron pipe was found in good condition, protruding approximately 6" out of the ground with the remnants of a wood and wire target lying around the area.

The following additional information was located and verified on this recovery:

Original description transcribed from the United States Geological Survey Bulletin Number 276 entitled “Results of Primary Triangulation and Primary Traverse Fiscal Year 1904-5" by Samuel S. Gannett.

On the east bank of Lonesome Lake Coulee, 6 miles southwest of Box Elder railroad station and 2 miles west of railroad track.

Station mark: An iron bench-mark post set 40 inches in ground.

Reference marks: Bottle 8 inches underground, true azimuth, 174 degree 40'; distant 5.8 feet from station; bottle 8 inches underground, true azimuth, 358 degree 16'; distant 5.7 feet from station.

At 2 degree azimuth and 5.7 feet from the station, a Carter’s One Full Quart ink bottle was found approximately 20" below the ground surface. The bottle was standing upright and was in excellent condition.

At 174 degree azimuth and 5.8 feet from the station, a clear one quart whiskey or beer bottle with a cork in it was found upright and approximately 10" below the ground surface. This bottle had a chip out of the lip, but was otherwise in excellent condition.

Both bottles were removed for photos, but have been replaced in their original positions with ½"x18" rebar placed over and alongside the bottles for easier future recovery. Each reference location had a flat stone placed over the location originally and each stone was also replaced over the reference location.

I did feel that this was the wrong thing to do and so the bottles were replaced in their original positions. Marked or un-marked, original un-disturbed evidence should be left as found.

Kurt

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Regarding PapaBear's comment/question:

"My assumption is that the location of the known first order station (MZ1808) was more accurate, and the discrepancy was mostly due to the uncertainty of the third order station (MZ1807), but I'm at a loss to find any way to put numbers on this uncertainty. I've seen accuracy estimates for this type of (pre-GPS) stations, but always as a fraction of the distance and azimuth from other stations, but what other stations? How do I turn this fraction into an uncertainty of the location as in +/- so many cm?"

My answer is that the likely error depends on the circumstances: 1) were the two survey points measured directly (like a triangulation station and its reference marks), 2) were the two survey points part of the same triangle of the triangulation? 3) were the two survey points part of the same project? 4) were the two survey points part of the same arc of triangulation? or, worst case 5) were the two survey points in different arcs of triangulation?

Case 1 - Standard practice from the 1950's to the 1980's (and probably much earlier) was to measure the distance from the triangulation station to the RMs with a steel tape in both metric and English units and then compare. Doing this should help eliminate errors. See USC&GS Special Publication #247, page 98 for text and page 99 for a photo showing a tape and plumb bob in use (http://docs.lib.noaa.gov/rescue/cgs_specpubs/QB275U35no247rev1959.pdf ) . In addition, the angles to the RMS were turned 6 times and averaged, so the azimuth to the RM should be very accurate. Any angles greater than 20 seconds from the mean were rejected. Twenty seconds over the 30 meters to an RM is only 3mm.) So, I would expect the RM's (assuming all marks are undisturbed) to be within a few cm of the given or computed position. Note, most RMs do not have separate positions in the NGS database, but as PapaBear mentioned, the positions can be computed from the description’s direction and distance information using the NGS "Forward" software available at: http://www.ngs.noaa.gov/TOOLS/Inv_Fwd/Inv_Fwd.html .

Case 2 - If the two points were part of the same triangle (that is, a triangle in which all angles were observed and perhaps all distances were computed from baselines some distance away). First-order standards were that triangle closures should not exceed a maximum of 3 seconds and the average closure should not exceed 1 second (SP#247, page 162). If we assume that the error in the sides is about the same magnitude as the error in the angles (I believe the specifications were designed that way), then one could compute the approximate error by using simple trigonometry. For a 10 mile distance and one second of error, the result is about 1/4 foot.

Case 3 - The two points are in the same project, but not directly connected. It is likely that points were in the same project if they have the same setting date and are in the same area. If this is the case, the one part in 100,000 (first-order standard), should apply. So, if one divides 100,000 by 5280, the result is about 19 miles, so a first-order point should be accurate to about one foot in about 19 miles.

Case 4 - Slightly less accurate then Case 3.

Case 5 - In some parts of the country there are arcs of triangulation that are parallel to each other with no cross connections. Two points within the same arc should be quite accurate, as described in Cases 3 and 4. However, in the case where two points in adjacent, but not connected arcs, are compared, the errors can be much larger. For example, there could be a situation where two arcs are about 20 miles apart, but the survey connection path may be 80 or 100 miles long! In this case, the error could be 4 or 5 feet or more.

Note, all of these are approximations.

The proportional errors for the different orders of triangulation are:

First-order - 1:100,000

Second-order, Class I - 1:50,000

Second-order, Class II - 1:20,000

Third-order, Class I - 1:10,000

Third-order, Class II - 1:5,000

-------------------------------------------------

PROBE - GEO Trailblazer mentioned using a stainless steel rod with a T handle. These can be found on-line by searching for "tile probe". I have also used them.

-------------------------------------------------

INTERSECTION STATIONS – It is probably true that land surveyors rarely use Intersection Stations in this age of satellite surveying. However, Intersection Stations are still quite valuable for positioning aerial and satellite imagery (since they can often be seen on the imagery and have known positions). Intersection stations were observed from at least three triangulation stations, two required for a fix and the third as a check. Four sets of angles (eight directions) were observed to the Intersection station from each triangulation station. Any angles greater than 5 seconds from the mean were rejected. For those interested, the specifications for surveying Intersection Stations are in SP#247, page 13 (four positions = observing the angle 8 times). Note, take special care when recovering Intersection Stations. Many times the original structure as been altered, rebuilt, moved, or confused with a nearby similar structure.

MARK RECOVERY – I would leave all marks in place. Even if some are not that valuable any longer, leave them in place for future surveyors doing historical positioning research, and so that future survey mark hunters can have the fun of recovering them. For those that would like to see what a bottle or clay pot looks like, see several photos in the article at: http://celebrating200years.noaa.gov/survey...come.html#intro . These photos are of marks in the NGS collection. These marks were removed when the stations were destroyed due to construction.

GeorgeL

NGS

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Regarding PapaBear's comment/question:

Case 1 - Standard practice from the 1950's to the 1980's (and probably much earlier) was to measure the distance from the triangulation station to the RMs with a steel tape in both metric and English units and then compare. Doing this should help eliminate errors. See USC&GS Special Publication #247, page 98 for text and page 99 for a photo showing a tape and plumb bob in use (http://docs.lib.noaa.gov/rescue/cgs_specpubs/QB275U35no247rev1959.pdf ) . In addition, the angles to the RMS were turned 6 times and averaged, so the azimuth to the RM should be very accurate. Any angles greater than 20 seconds from the mean were rejected. Twenty seconds over the 30 meters to an RM is only 3mm.) So, I would expect the RM's (assuming all marks are undisturbed) to be within a few cm of the given or computed position. Note, most RMs do not have separate positions in the NGS database, but as PapaBear mentioned, the positions can be computed from the description’s direction and distance information using the NGS "Forward" software available at: http://www.ngs.noaa.gov/TOOLS/Inv_Fwd/Inv_Fwd.html .

Case 2 - If the two points were part of the same triangle (that is, a triangle in which all angles were observed and perhaps all distances were computed from baselines some distance away). First-order standards were that triangle closures should not exceed a maximum of 3 seconds and the average closure should not exceed 1 second (SP#247, page 162). If we assume that the error in the sides is about the same magnitude as the error in the angles (I believe the specifications were designed that way), then one could compute the approximate error by using simple trigonometry. For a 10 mile distance and one second of error, the result is about 1/4 foot.

Case 3 - The two points are in the same project, but not directly connected. It is likely that points were in the same project if they have the same setting date and are in the same area. If this is the case, the one part in 100,000 (first-order standard), should apply. So, if one divides 100,000 by 5280, the result is about 19 miles, so a first-order point should be accurate to about one foot in about 19 miles.

Case 4 - Slightly less accurate then Case 3.

Case 5 - In some parts of the country there are arcs of triangulation that are parallel to each other with no cross connections. Two points within the same arc should be quite accurate, as described in Cases 3 and 4. However, in the case where two points in adjacent, but not connected arcs, are compared, the errors can be much larger. For example, there could be a situation where two arcs are about 20 miles apart, but the survey connection path may be 80 or 100 miles long! In this case, the error could be 4 or 5 feet or more.

GeorgeL

NGS

Thanks George

These stations were set years apart, MZ1808 (1st order) in 1862 (By Bache) and MZ1807 (3rd order) in 1835 (by Borden). The 1st order station was part of the EOA so it's accuracy was probably better than 1st order. The 1835 station was done in the early Borden survey, so they were not part of the same survey or project. But the expertise of the survey parties was impeccable, to say the least. How many times would you find a Borden and a Bache station 11 feet apart and both with the original copper bolts!.

Our measured distance exactly agreed with the 1896 measurement to within a cm. The calculated distance from the 2 datasheets wa about 5 inches (12 cm) short. So in this case (as I would say in most similar cases) the local measurement is a better method for finding a mark that calculations from unconnected triangulation stations. INCIDENTALLY - the 1896 measurement (in meters) does not agree with the number given in feet. It`s off by almost 3 inches. I must assume they measured in meters (accurately), and converted to feet, incorrectly.

Note this vintage report:

Compute the 2 numbers in the first sentence and you'll see what I mean. It's also interesting that both numbers were repeated in subsequent logs, without any mention of the error.

Edited by Papa-Bear-NYC

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Notice that 11.783 feet is 3.5915 meters, same digits in a different order. So was the mistake using the wrong number for the conversion to feet, or was it a typo in recording the number of meters originally?

Edited by Bill93

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Notice that 11.783 feet is 3.5915 meters, same digits in a different order. So was the mistake using the wrong number for the conversion to feet, or was it a typo in recording the number of meters originally?

The number of meters given was dead on. So the mistake was NOT a typo in transcribing digits. In other words the meters were right, the feet were wrong. Besides the feet are in parenthesis so I assume the measurement was done in meters. The Procedure George outlined (measuring both meters and feet as a cross check) may not have been used in 1885.

Maybe the guy was converting in his head or on the back of an envelope. Or maybe they converted it back in the office and just plain made a blunder. The correct feet would be 11.547 - which is not any kind of transcription of 11.783. It threw us off for a while till Dave (ddnutzy - my partner in the recovery) said, "Just use meters". Then we found the bolt.

Edited by Papa-Bear-NYC

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Ok, then, the theory is that the guy doing the conversion to feet was the one who transcribed the meter digits in the wrong order.

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