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tosborn

Reporting Intersection Stations to NGS

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In late August we had a discussion (link) about reporting destroyed intersection stations (e.g. water towers, church steeples, etc) to NGS. It has been stated by some here that while NGS (Deb Brown) no longer wishes to receive positive recovery reports on intersection stations, destroyed interesection stations should continue to be reported to NGS so that they can be removed "from the active database to reduce clutter."

 

Shortly after that discussion I emailed Deb Brown the following:

 

Deb:

 

In the past you've indicated that you would rather NOT receive GEOCAC

recovery reports on intersection stations. Does that also apply to destroyed

reports on intersection stations?

 

The reason I ask is that there is currently an assumption among GEOCAC

participants that while you DON'T want recovery reports on intersection

stations, you DO want destroyed reports when there is evidence that the

intersection station has been destroyed.

 

Yesterday I received the following response from Deb:

 

Sorry for the delay in responding.

 

Typically I'd rather not get info of any sort on intersection stations

or landmark stations, however, if I get them I process them. The advent

of GPS has eliminated their use.

 

deb

 

So I would humbly suggest that we respect Deb's wishes and refrain from submitting info of any sort to NGS concerning intersection stations.

 

Tim

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Being a newbe to terms, what is an intersection station?

There are two kinds of answers:

 

1) Structures that are man made (mostly) such as towers, church steeples, chimneys, Building tops (The Empire State Building), fixed navigation aides and occasionally mountain peaks (e.g the Devil's tower) AND which provide no place for a surveyor to set up his equipment.

 

2) Stations that were observed from other stations, but from which no observations were made. For example: a surveyor could set up his stuff on a hill top and observe a church steeple, but he could not set up on the steeple and observe the hill top.

 

A rule of thumb is if it's not a disk on the ground (or for old stations a drill hole or copper bolt) it has a good chance of being an intersection station.

 

The name comes from the fact that the observation lines drawn from the other stations to the intersection station "intersect" at that station. The position on a map can be determined by computations based on the triangles formed by these intersecting lines.

 

Be careful - some building tops, church steeples, etc., DO provide a spot for a surveyor, such as the belfry below the steeple, or somewhere on the roof of the building. The surveyor will usually create a mark (sometimes a disk or merely a copper tack) and determine that it is exactly under the steeple, etc. and thus make observations. These are not intersections stations but are true triangulation stations. Example : High Bridge Tower in Manhattan.

Edited by Papa-Bear-NYC

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Being a newbe to terms, what is an intersection station?

There are two kinds of answers:

 

1) Structures that are man made (mostly) such as towers, church steeples, chimneys, Building tops (The Empire State Building), fixed navigation aides and occasionally mountain peaks (e.g the Devil's tower) AND which provide no place for a surveyor to set up his equipment.

 

2) Stations that were observed from other stations, but from which no observations were made. For example: a surveyor could set up his stuff on a hill top and observe a church steeple, but he could not set up on the steeple and observe the hill top.

 

A rule f thumb is if it's not a disk on the ground (or for old stations a drill hole or copper bolt) it has a good chance of being an intersection station.

 

The name comes from the fact that the observation lines drawn from the other stations to the intersection station "intersect" at that station. The position on a map can be determined by computations based on the triangles formed by these intersecting lines.

 

Be careful - some building tops, church steeples, etc., DO provide a spot for a surveyor, such as the belfry below the steeple, or somewhere on the roof of the building. The surveyor will usually create a mark (sometimes a disk or merely a copper tack) and determine that it is exactly under the steeple, etc. and thus make observations. These are not intersections stations but are true triangulation stations. Example : High Bridge Tower in Manhattan.

 

Interesting, The cross on a church steeple or the chimney of a biulding could be triangulation station OR an intersection station.

 

Is there a way to tell the difference? or will it be indicated on the data sheet. and,

If a triangulation station, do I just take a photo of the cross?, or do I need to search for, and find, the mark?

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Being a newbe to terms, what is an intersection station?

...

Be careful - some building tops, church steeples, etc., DO provide a spot for a surveyor, such as the belfry below the steeple, or somewhere on the roof of the building. The surveyor will usually create a mark (sometimes a disk or merely a copper tack) and determine that it is exactly under the steeple, etc. and thus make observations. These are not intersections stations but are true triangulation stations. Example : High Bridge Tower in Manhattan.

 

Interesting, The cross on a church steeple or the chimney of a biulding could be triangulation station OR an intersection station.

 

Is there a way to tell the difference? or will it be indicated on the data sheet. and,

If a triangulation station, do I just take a photo of the cross?, or do I need to search for, and find, the mark?

The cross and steeple are almost always intersections stations NOT triangulations stations. The chimney NEVER (where is a surveyor going to set up on or under a chimney.

 

I only mentioned the possibility in that last sentence because there are a few such stations. The ones I know of are a few stations used in the 1903-5 triangulation of New York City, where there were few hills or peaks that stood above the city scape. (like This one) It is fairly unlikely that there are many others around. For one thing it is difficult and dangerous for a surveyor to set up in such places, and secondly it's non-trivial to establish that the surveyor's set-up is directly under the cross or steeple. So I probably should not have written that sentence. But quod scripsi scripsi.

 

Furthermore, intersections stations are almost always third order stations, have no reference marks and have no box score on the datasheet.

 

Bottom line: if you see a cross or a steeple or a chimney it's an intersection station.

Edited by Papa-Bear-NYC

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Re: "Triangulation Station on Chimney of Permanent Building."

 

Great posts, Kurt!

 

The next time someone asks why I did not choose "Surveyor" as an occupation, I'll reach in my wallet and pull out this photo.

 

-Paul-

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Bottom line: if you see a cross or a steeple or a chimney it's an intersection station.

 

What if it is marked as a BM?

 

MZ2056

1/1/1960 by CGS (FIRST OBSERVED)

DESCRIBED BY COAST AND GEODETIC SURVEY 1960 (HRL) STATION IS LOCATED IN THE NORTH-CENTRAL SECTION OF PITTSFIELD, ABOUT 185 FEET EAST-NORTHEAST OF THE INTERSECTION OF NORTH AND BRADFORD STREETS AND 0.15 MILE NORTH-NORTHEAST OF THE COMMON. STATION IS A CROSS THAT IS GOLD IN COLOR AND MOUNTED AT THE APEX OF A CUBICAL SHAPED SPIRE THAT IS MOUNTED ON THE TOP OF A 180 X 120 FOOT STONE BUILDING THAT IS WHITE IN COLOR. THE OVERALL HEIGHT OF THE CROSS IS APPROXIMATELY 200 FEET. POINT OBSERVED WAS THE CENTER OF THE CROSS.

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Bottom line: if you see a cross or a steeple or a chimney it's an intersection station.

 

What if it is marked as a BM?

 

MZ2056

1/1/1960 by CGS (FIRST OBSERVED)

DESCRIBED BY COAST AND GEODETIC SURVEY 1960 (HRL) STATION IS LOCATED IN THE NORTH-CENTRAL SECTION OF PITTSFIELD, ABOUT 185 FEET EAST-NORTHEAST OF THE INTERSECTION OF NORTH AND BRADFORD STREETS AND 0.15 MILE NORTH-NORTHEAST OF THE COMMON. STATION IS A CROSS THAT IS GOLD IN COLOR AND MOUNTED AT THE APEX OF A CUBICAL SHAPED SPIRE THAT IS MOUNTED ON THE TOP OF A 180 X 120 FOOT STONE BUILDING THAT IS WHITE IN COLOR. THE OVERALL HEIGHT OF THE CROSS IS APPROXIMATELY 200 FEET. POINT OBSERVED WAS THE CENTER OF THE CROSS.

 

Datasheets will usually tell you the whole story, too:

1/1/1960 by CGS (FIRST OBSERVED)

First Observed means that it's an intersection station, and was viewed upon for measurements. Also, the line:

MZ2056_MARKER: 91 = CHURCH CROSS

Marker types that are numbers are intersection stations, and letters are other types.

 

I'm sure there's a least one exception to these rules above, but I haven't seen them yet.

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>POINT OBSERVED WAS

 

This says they were not set up on the point, but rather that it is an intersection station. The other clues confirm it.

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JC1594 is, to me, ambiguous.

 

The description refers to a nail in a plank, which sounds like something to position an instrument over, not observe from the ground.

 

STATION DESCRIPTION

JC1594

JC1594'DESCRIBED BY COAST AND GEODETIC SURVEY 1871 (CHB)

JC1594'ON TOP OF CAP OF STANDPIPE, 180 FEET HIGH, AT CORNER OF GRAND

JC1594'AVENUE AND FOURTEENTH STREET, ST. LOUIS. MARKED BY NAIL IN PLANK

JC1594'NAILED TO TIMBERS WHICH ARE FRAMED IN BRICK MASONRY AT TOP OF

JC1594'STANDPIPE. FOUR ARROWS POINTING TOWARD STATION ARE CUT IN TOP

JC1594'OF IRON CAP OF STANDPIPE.

 

That said, it's a standpipe tank, which is normally an intersection station. And the "history" section says it was "first observed," not monumented.

 

-ArtMan-

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JC1594 is, to me, ambiguous.

 

The description refers to a nail in a plank, which sounds like something to position an instrument over, not observe from the ground.

 

STATION DESCRIPTION

JC1594

JC1594'DESCRIBED BY COAST AND GEODETIC SURVEY 1871 (CHB)

JC1594'ON TOP OF CAP OF STANDPIPE, 180 FEET HIGH, AT CORNER OF GRAND

JC1594'AVENUE AND FOURTEENTH STREET, ST. LOUIS. MARKED BY NAIL IN PLANK

JC1594'NAILED TO TIMBERS WHICH ARE FRAMED IN BRICK MASONRY AT TOP OF

JC1594'STANDPIPE. FOUR ARROWS POINTING TOWARD STATION ARE CUT IN TOP

JC1594'OF IRON CAP OF STANDPIPE.

 

That said, it's a standpipe tank, which is normally an intersection station. And the "history" section says it was "first observed," not monumented.

 

-ArtMan-

One clue to me is that it's a first order station. That tells me it was observed from and is thus a triangulation station, even though it has no box score. The only way to resolve it is to find the original survey data, something out or our ken.

 

OTOH, the scaffolding and planks may have disappeared long ago. I guess in that case it would mean 1t's "destroyed" even though the stand-pipe still stands.

 

I found one like that:

 

KU3955|---------------------------------------------------------------------|
KU3955| PID	Reference Object					 Distance	  Geod. Az  |
KU3955|														   dddmmss.s |
KU3955| CB7395 SHIRE WM 2						   18.860 METERS 06734	 |
KU3955| CB7394 SHIRE WM 1						   37.640 METERS 10445	 |
KU3955| CB7393 SHIRE RM							 16.940 METERS 10446	 |
KU3955| KU4022 MANHATTAN RIVERSIDE BAP CH TWR	  APPROX. 2.4 KM 2071426.5 |
KU3955| KU3891 FORT LEE CHRIST ORPH HOME FLAG	  APPROX. 2.2 KM 3133640.3 |
KU3955| KU3890 PALISADES						   APPROX. 2.5 KM 3382747.7 |
KU3955|---------------------------------------------------------------------|
KU3955
 ...
KU3955_MARKER: X = CHISELED CROSS
KU3955_SETTING: 0 = UNSPECIFIED SETTING
 ...
KU3955
KU3955'DESCRIBED BY COAST AND GEODETIC SURVEY 1930 (CAE)
KU3955'STATION IS ON THE E BANK OF THE HUDSON RIVER, BETWEEN 151ST AND
KU3955'152ND STREETS, ABOUT 30 METERS W OF RIVERSIDE DRIVE, A BAND STAND
KU3955'ABOUT 14 METERS IN DIAMETER, WITH LARGE GRANITE PILLARS SUPPORTING
KU3955'A RED CONICAL ROOF.  IT IS A MEMORIAL ERECTED BY CREW OF U.S.S.
KU3955'NEW HAMPSHIRE FOR LOST SHIPMATES.
KU3955'
KU3955'STATION IS FINIAL IN CENTER OF ROOF.  A CROSS WAS CHISELED ON
KU3955'FLOOR BENEATH THE FINIAL.
KU3955'
KU3955'REFERENCE MARK IS A STANDARD DISK CEMENTED IN DRILL HOLE IN
KU3955'CONCRETE WALK ON W SIDE OF RIVERSIDE DRIVE.
KU3955'
KU3955'WITNESS MARK NO.1 IS A CROSS CUT IN TOP OF CURB ON E SIDE OF
KU3955'DRIVE.  AN ARROW POINTING TO STATION WAS ALSO CUT IN CURB S OF THE
KU3955'CROSS.
KU3955'
KU3955'WITNESS MARK NO. 2 IS CENTER OF SMALL DRINKING FOUNTAIN.
KU3955

 

Unlike your situation, the dome with it's finial are long gone, but the cross on the floor remains. And alas, it's only a third order station. But I concluded it was a triangulation station, not an intersection station since it 1) has a box score (indicating measurements were taken to those points) and 2) had reference marks.

 

Note the ambiguity between the marker type "Chiseled Cross" and text "Station is finial in center of roof". But then immediately after, the text "A cross was chiseled on floor beneath finial".

 

I think "First observed" doesn't prove the case. Yes the surveyor didn't build the stand pipe, but he evidently did go up there and set up his instrument. If you consider the nail to be the station, then the surveyor did "monument" the station when he drove the nail into the plank.

 

I think we are losing sight of the forest because of the trees. The point is to stop reporting these to the NGS. Really. Stop reporting.

 

Although it's fun for us to discuss these one-offs on this forum (and I'm sure this discussion will continue here), the NGS really has other things to do with their scarce resources.

 

For us, maybe we should have a contest on the most ambiguously described station, and then (like Sherlock Holmes) argue for a particular interpretation, which is basically what I did above. And by the way, I love that shot of the surveyor sitting on the chimney.

Edited by Papa-Bear-NYC

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