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JL_HSTRE

Are These All The Same Benchmark?

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The lighthouse near me appears to be listed 4 times. This seems particularly odd since the lighthouse was built in 1860 and has not been moved or significantly modified since then. Am I missing something or are all 4 of these marks for the lighthouse itself? Any idea why it would be listed repeatedly?

 

AD6442

AD6443

AD6444

AD6445

 

There is also a 5th mark associated with the lighthouse, but it is clearly listed as a drill hole.

 

On the concrete railing of the stairs leading up the hill to the base of the lighthouse is this disk which I'm guessing is a reference mark?

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Go here for the CG list of marks and the reading of the official recoveries are a little easier, and a few pictures from the peanut gallery - (geocachers/GC BM hunters).

 

I like to look at pictures - It helps bunches even if the pictures are of the surrounding areas.....

 

I will let someone else answer his questions while I look at all of the logs and picts.

 

Shirley~

 

~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 

PS: If no one else has answered by the time that John gets home from work - 9 PM, he might consider answering......

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The lighthouse near me appears to be listed 4 times. This seems particularly odd since the lighthouse was built in 1860 and has not been moved or significantly modified since then. Am I missing something or are all 4 of these marks for the lighthouse itself? Any idea why it would be listed repeatedly?

 

AD6442

AD6443

AD6444

AD6445

 

There is also a 5th mark associated with the lighthouse, but it is clearly listed as a drill hole.

 

On the concrete railing of the stairs leading up the hill to the base of the lighthouse is this disk which I'm guessing is a reference mark?

 

It appears that all four are the same lighthouse, but the point intersected is different for each one. These are intersection stations that were sighted on from a distance, and it appears that since there was no clearly defined point of intersection listed on the datasheet, the surveyor picked a point to sight on and monumented the new point - hence the different PIDs.

 

The disk on the stairs is most likely tidal mark 3 (PID AD2999).

 

Just my impression of how things look.

 

John

Edited by 2oldfarts (the rockhounders)

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AD6445 reads: 01/01/1970 by NGS (GOOD)

RECOVERY NOTE BY NATIONAL GEODETIC SURVEY 1970 (PEC) THE STATION WAS RECOVERED AS DESCRIBED. POINT INTERSECTED WAS THE FINIAL AT TOP AND CENTER.

 

From this I am going to figure that the NGS made the call that this was the point intersected all along (beginning in the 1800's) This would make sense as alsmost every intersection point I have ever read about was the very top of the tower, cupola, church spire, chimney etc.

 

The more interesting question might be - why barely any to no specific info on the original work done by the survey team is listed. Were records lost somehow? Some of the folks on here may have a very good explanation for why these are so undescriptive.

 

I agree totally with John that the disk found is the tidal mark. The reference mark drill hole is just that - a simple drill hole in the floor.

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If you look at the adjusted coordinates on the NGS datasheets, you will see all 4 have different coordinates, which is why I suspect that each surveyor located on slightly different points on the lighthouse. One description says the finial and one says the walkway on the north/northeast edge. The first 2 recovers for AD6445 talk about a new station being created and that the new station is adequate for recovery of this station.

 

It would be nice if the NGS were to read these forums and offer their opinions.

 

John

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John - point taken on the walkway description. I didn't catch that, but - that is a strange spot to choose when the top is 99.999999% of the time the intersection spot used. That choice simply adds to the oddity of these marks. Yes - NGS comments on this one would be great. We all seem to have some good questions here.

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Here's my take after examining the NGS data sheets and plotting the coordinates. I think there are 3 horizontal triangulation points, with the finial being one and also having two additional intersection measurements, plus the independent tidal station, for a total of 6 data sheets. In approximately chronological order:

 

AD6443 JUPITER INLET LH 1883 was an occupied tri-station, because it has a box score. It lies within half a foot of the later measurement of the finial, and the accuracy may have even been such that it was with an instrument set up over the finial using a temporary platform. They didn't have OSHA to restrict them.

 

AD6444 JUPITER INLET LH 1929 with no other description was probably an intersection of the finial, again within half a foot.

 

AD6442 JUPITER INLET LH EC 1929 is an "eccentric" station set up near another station in a place more accessible (or in other cases with better visibility). It is a tri-station with a box score. It is on the WSW side, probably on the same platform as AD6446 and at nearly the same radius from the finial. They measured 2.530 meters (8.3 ft) at 75+ degrees to AD6444, their measurement of the finial.

 

AD6445 JUPITER INLET LH 1934 is an intersection station identified by the 1970 report as the finial.

 

AD6446 JUPITER INLET LH EC [1934] is a drill hole in the floor of an upper platform, NW side of the lighthouse, which was an occupied tri-station that has a box score.

 

AD2999 TIDAL 3 is in a lower landing of the stair, about 10 ft above ground, and is a disk set in a concrete railing. It has only HH2 handheld horizontal coordinates but an accurate elevation.

Edited by Bill93

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Bill -

 

You may be right, but it has always been my understanding that intersection points like the finial were not "occupied" but instead measured from a dustance. If it having a boxscore makes a difference to this understanding - then I may be learning something new (which happens all the time on this!)

Edited by frex3wv

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1) FWIW the lighthouse is 108 ft tall on a 38-40 ft tall hill in an area that is otherwise almost entirely 10 ft or less above sea level. So the top of the lighthouse should be visible from basically anywhere.

 

2) What is a "finial" that several of you mention?

 

3) For purposes of logging my benchmark finds on geocaching.com, is it appropriate to log finds all 4 of the benchmarks representing the lighthouse itself if one visits the lighthouse?

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Bill -

 

You may be right, but it has always been my understanding that intersection points like the finial were not "occupied" but instead measured from a dustance. If it having a boxscore makes a difference to this understanding - then I may be learning something new (which happens all the time on this!)

Ok I'm still learning and now it shows. What is a box score? What is its significance? And how do I recognize that a mark has one of these on datasheet?

 

The final is the element(sometimes decorative) on the very top of an object. It isgenerally easy spot from all directions and angles hence the reason it is most commonly the point that is used to site on from a distance.

 

You can log all of them but if they ever changed the finial then in an ngs log it should be marked as destroyed or not found. In the case of the description that is talking about the holes in the platform you would need to find the exact holes that match the description to log that point because the holes are the true mark in that case.

Edited by CityHuntersBJB

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If it were me, I would log AD6445 and leave the rest alone. While it is fun to log these intersection marks (especially when no one else ever has) the NGS isn't interested in them anymore. Just an FYI.

 

If you found the disk too, I would also log AD2999.

 

A finial is a piece at the very highest point of the lighthouse. The very top of that piece would be the spot measured etc.

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Bill -

 

You may be right, but it has always been my understanding that intersection points like the finial were not "occupied" but instead measured from a dustance. If it having a boxscore makes a difference to this understanding - then I may be learning something new (which happens all the time on this!)

Ok I'm still learning and now it shows. What is a box score? What is its significance? And how do I recognize that a mark has one of these on datasheet?

 

Once you know what it is, the box score is rather easy to see. Here is the box score from AD6442:

 

AD6442
AD6442|---------------------------------------------------------------------|
AD6442| PID    Reference Object                     Distance      Geod. Az  |
AD6442|                                                           dddmmss.s |
AD6442| AD6444 JUPITER INLET LH 1929                 2.530 METERS 07518     |
AD6442| AD6479 HOTEL 1929                          APPROX.18.6 KM 1651152.1 |
AD6442| AD6610 HOTEL ALBA CUPOLA                   APPROX.25.6 KM 1705654.9 |
AD6442| AD6498 KELSEY CITY BLACK TANK              APPROX.16.4 KM 1782926.6 |
AD6442| AD6420 JUPITER WEST RADIO TOWER            152.737 METERS 26228     |
AD6442|---------------------------------------------------------------------|
AD6442

 

It lists distances and azimuths to other marks. More info available here:

http://www.holoscenes.com/cgi-bin/moin.cgi/box%20score

 

NGS>GPX can translate them into child waypoints, though by default it doesn't translate those with approximate distances. (Note that, as some reference objects in a box score are some distance away, you might have to zoom out a bit to see them on the little map in GSAK.)

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Ok I'm still learning and now it shows. What is a box score? What is its significance? And how do I recognize that a mark has one of these on datasheet?

 

 

CityHuntersBJB, you can also read NGS Surveyors excellent pinned topic on triangulation stations (which have the box scores) at:

 

http://forums.Groundspeak.com/GC/index.php?showtopic=185361

 

Although EdrickV has answered your question with a more detailed explanation, Gc.com also explains it in their benchmarks Q&A section:

 

http://www.geocaching.com/mark/#boxscore

 

When searching for triangulation stations (my personal favorite benchmarks), you need this box score information to help find the reference marks. A lot of times you may find a reference mark first, then use a reverse compass azimuth from the box score and be able to measure off the direction and distance to the main triangulation station disk.

 

Box scores are why it's a good idea to purchase a double-sided tape measure that has feet(SAE) on one side and meters(metric) on the other side. You'll find most box scores have the distance in meters, but the other reference objects listed in benchmark descriptions have the distance in feet (ie from center of road, distance to trees, buildings, etc).

 

Here is one tape measure I have several of:

 

http://www.harborfreight.com/1-2-half-inch-x-330-ft-open-reel-measuring-tape-36819.html

Edited by LSUFan

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Ok I'm still learning and now it shows. What is a box score? What is its significance? And how do I recognize that a mark has one of these on datasheet?

 

 

CityHuntersBJB, you can also read NGS Surveyors excellent pinned topic on triangulation stations (which have the box scores) at:

 

http://forums.Groundspeak.com/GC/index.php?showtopic=185361

 

Although EdrickV has answered your question with a more detailed explanation, Gc.com also explains it in their benchmarks Q&A section:

 

http://www.geocaching.com/mark/#boxscore

 

When searching for triangulation stations (my personal favorite benchmarks), you need this box score information to help find the reference marks. A lot of times you may find a reference mark first, then use a reverse compass azimuth from the box score and be able to measure off the direction and distance to the main triangulation station disk.

 

Box scores are why it's a good idea to purchase a double-sided tape measure that has feet(SAE) on one side and meters(metric) on the other side. You'll find most box scores have the distance in meters, but the other reference objects listed in benchmark descriptions have the distance in feet (ie from center of road, distance to trees, buildings, etc).

 

Here is one tape measure I have several of:

 

http://www.harborfreight.com/1-2-half-inch-x-330-ft-open-reel-measuring-tape-36819.html

 

Both NGS>GPX and DSWorld can compute reference mark locations from the box score info and give you GPS coordinates, which I think might be a little quicker then using a tape. (Especially if you don't have a compass, which I didn't have when I found my first triangulation station. Of course, that station was a little easier to find then most I imagine. :) )

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The use of eccentric stations at lighthouses was not at all uncommon. Since these structures often provide excellent visibility over many miles they were excellent locations for geodetic observations without having to build a tall, expensive and temporary observation tower (after 1927 referenced as Bilby Towers). Generally eccentric stations were set where the field team could not easily occupy the primary point such as the finial or peak of a lighthouse. In numerous cases eccentric stations were established a ground level when an existing tradition triangulation station could not be directly occupied for some reason. The eccentric station could be either a temporary point or one that was more permanent such as drill hole or a disk. The field team would perform the direction (angle) observations at the eccentric station and then very accurately measure the distance from the eccentric station to the point they really wanted the coordinates for. Using these data the field computer could perform what was referred to as a reduction to center which is a neat little trick that allows you to modify the observations from the eccentric station to make them look like they were actually observed from the primary point (lighthouse finial etc.). You can find more details on this procedure in USC&GS Special Publication 247 "Manual of Triangulation" on pages 114-115 and 154-157.

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