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Quick question on Intersection Stations.


TillaMurphs

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If the datasheet does not specifically mention in the description that the station is an intersection station (or was intersected) is there a way to positively identify if the station is an Intersection station?

 

I see datasheets with adjusted coordinates and no mention of setting type and figure that is a good indicator of an intersection station but I suspect that more clues are needed to absolutely identify an Intersection station?

 

Thanks,

 

- - The TillaMurphs

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Hi TillaMurphs:

 

Good question. In my experience, it's sometimes tricky to tell. One sure way is in the History section (where the dates are listed), it may say "First Observed". Then I went to find one like that and couldn't! All the ones around here seem to say "Monumented" in the History section.

 

So, the next clue seems to be the designation, like

DX4823 - LA HABRA CH OF OUR LADY CROSS

 

The clue is "CROSS".

 

Then there is the actual description. It may say something like:

"...THE CROSS WAS INTERSECTED..."

 

Sometimes, I've actual had to go there & look at it.

If there is a foolproof way, I'm not enough of a fool to have found it yet. :rolleyes:

 

Klemmer

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If the datasheet does not specifically mention in the description that the station is an intersection station (or was intersected) is there a way to positively identify if the station is an Intersection station?

 

I see datasheets with adjusted coordinates and no mention of setting type and figure that is a good indicator of an intersection station but I suspect that more clues are needed to absolutely identify an Intersection station?

 

Thanks,

 

- - The TillaMurphs

 

 

The "Marker Type" will often tell you that you would be looking for a tower, belfry, cupola, stack, or something of that nature. Often it is identified in the description as to what the 'mark' is.

 

The following list is from the Hippo List.

 

Monumentation Category Monumentation Code Definition

Not for Landmark Stations

O, U A Aluminum marker other than a disk included elsewhere in table

O, U B Bolt

O, U C Cap of cap-and-bolt pair

D DA Astro pier disk

D DB Bench mark disk

D, U DD Survey disk (other agency)

D, U DE Traverse station disk

D DG Gravity station disk

D, U DH Horizontal control disk

D DJ Tidal station disk

D DK Gravity reference mark disk

D DM Magnetic station disk

D, U DO Disk not specified (see description)

D DP Base line pier disk

D DQ Calibration base line disk

D, U DR Reference mark disk

D, U DS Triangulation station disk

D DT Topographic station disk

D DU Boundary marker

D DV Vertical control disk

D DW NOS hydrographic survey disk

D, U DZ Azimuth mark disk

O, U E Earthenware pot

R F Flange-encased rod

O, U G Glass bottle

O, U H Drill hole

R, U I Metal rod

O, U J Earthenware jug

O, U K Clay tile pipe

O, U L Gravity plug

O, U M Ammo shell casing

O, U N Nail

O, U O Chiseled circle

O, U P Pipe cap

O, U Q Chiseled square

O, U R Rivet

O, U S Spike

O, U T Chiseled triangle

O, U U Concrete post (without other marks)

O, U V Stone monument

O, U W Unmonumented

O, U X Chiseled cross

O, U Y Drill hole in brick

O, U Z See description

Landmarks not Listed

L 0 Other mark or intersection station, see description

Natural Objects

L 01 Lone tree

L 02 Conspicuous rock

L 03 Mountain peak

L 04 Rock pinnacle

L 05 Rock awash

Waterfront Landmarks and Visual Aids to Navigation

L 11 Piling

L 12 Dolphin

L 13 Lighthouse

L 14 Navigation light

L 15 Range marker

L 16 Daybeacon

L 17 Flag tower

L 18 Signal mast

Aeronautical and Electronic Aids to Navigation

L 21 Airport beacon

L 22 Airway beacon

L 23 VOR antenna

L 24 REN antenna

L 25 Radar antenna

L 26 Spherical radome

L 27 Radio range mast

L 28 LORAN mast

Broadcast and Communications Facilities

L 41 Antenna mast

L 42 Radio/TV mast

L 43 Radio/TV tower

L 44 Microwave mast

L 45 Microwave tower

Tanks and Towers

L 51 Tank

L 52 Standpipe tank

L 53 Elevated tank

L 54 Water tower

L 55 Tower

L 56 Skeleton tower

L 57 Lookout tower

L 58 Control tower

Miscellaneous Landmarks

L 61 Pole

L 62 Flagpole

L 63 Stack

L 64 Silo

L 65 Grain elevator

L 66 Windmill

L 67 Oil derrick

L 68 Commercial sign

L 69 Regulatory sign

L 70 Monument

L 71 Boundary monument

L 72 Cairn

L 73 Lookout house

L 74 Large cross

L 75 Belfry

Features of a Building

L 81 Gable

L 82 Finial

L 83 Flagstaff

L 84 Lightning rod

L 85 Chimney

L 86 Cupola

L 87 Dome

L 88 Observatory dome

L 89 Spire

L 90 Church spire

L 91 Church cross

L 92 Antenna on roof

L 93 Microwave antenna on building

L 94 Rooftop ventilator

L 95 Rooftop blockhouse

 

Fairly easy to determine which are intersection stations.

 

You missed out on that contest! You got points for the different marker types.

 

 

John

 

 

Edit: guess I'm a pretty fair fool..... :D:rolleyes:

Edited by 2oldfarts (the rockhounders)
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If the datasheet does not specifically mention in the description that the station is an intersection station (or was intersected) is there a way to positively identify if the station is an Intersection station?

 

I see datasheets with adjusted coordinates and no mention of setting type and figure that is a good indicator of an intersection station but I suspect that more clues are needed to absolutely identify an Intersection station?

 

Absolutely? An intersection station is a horizontal control point that was not occupied with a theodolite or GPS, and the published datasheet doesn't tell you that, so you can never know absolutely unless you have access to the original observation notes. There are a couple of reliable clues, though.

  • Intersection stations will be 3rd order horizontal control.
  • Intersection stations will be established with "classical" methods.
  • Intersection stations will be artifacts whose purpose is not primarily geodetic. i.e. they will be buildings or structures that predate the first observation.
  • Intersection stations will be points that would not be "occupied", i.e. if you can't envision a person putting a theodolite at the point, there's a good chance it's an intersection station.
  • If you see "the point observed was..." in the description.
  • If you have a map of the triangulation network, and the lines meeting at the point are dashed or dotted.

Even mountain peaks might be intersection stations if no one bothered to hike up to the top with heavy equipment and take sightings on other stations of the network.

Edited by holograph
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There are a number of cases that I am familiar with where there is a monumented station, and a structure also which would be like an intersection station. The descriptions could make this unclear.

 

Without looking at the data sheet, one example is the old Daniels and Fisher tower in Denver that was a tower and it was also occupied and perhaps monumented at a point below the top. Similarly a lot of fire towers have the tower and a monument placed underneat.

 

So description of a station as on object like a tower does not necessarily mean it was strictly an intersection station or was not occupied. You have multiple functions at a station, targets, lights, instrument stands and monuments.

 

- jlw

Edited by jwahl
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Klemmer – thanks for the input.

 

John – thanks for the list. Oooo. That sounded like a fun contest. Sorry me missed it.

 

Holograph – thanks for the concise checklist. I am printing out your list to use for reference - it’s great. I usually skip over the text mentioned in your second bullet – now I will start paying attention to that. In the past I had wondered about the dashed lines in triangulation maps – thanks for clearing that up also.

 

There are a number of cases that I am familiar with where there is a monumented station, and a structure also which would be like an intersection station. The descriptions could make this unclear.

 

Without looking at the data sheet, one example is the old Daniels and Fisher tower in Denver that was a tower and it was also occupied and perhaps monumented at a point below the top. Similarly a lot of fire towers have the tower and a monument placed underneath.

 

So description of a station as on object like a tower does not necessarily mean it was strictly an intersection station or was not occupied. You have multiple functions at a station, targets, lights, instrument stands and monuments.

 

- jlw

AHA! AHA! BINGO!

 

THAT is what I was trying to figure out!!

 

We have found 3 fire lookout towers, each with a disk in the center underneath. We are having trouble figuring out what exactly a “Found” would consist of because we found the four tower foundation supports and the disk but the tower structure is gone.

 

For example, we found the disk and the 4 foundation supports for RD1845. I have copied the text below. In the 1954 description. It says the tower was destroyed but the station was found in good condition? Huh?

 

Can somebody explain that? Isn’t the center of the tower the “station”?

 

Before I log RD1854 I am trying to decide if I should call it destroyed because the tower structure is gone or call it found because we found the disk?

 

RD1845 DESIGNATION - MT GAULDY LOT

RD1845 PID - RD1845

RD1845 STATE/COUNTY- OR/TILLAMOOK

RD1845 ___________________________________________________________________

RD1845* NAD 83(1991)- 45 11 11.93604(N) 123 51 27.53161(W) ADJUSTED

RD1845* NAVD 88 - **(meters) **(feet)

RD1845 ___________________________________________________________________

RD1845 HORZ ORDER - THIRD

RD1845

RD1845 HISTORY - Date Condition Report By

RD1845 HISTORY - 1936 MONUMENTED USFS

RD1845 HISTORY - 1941 SEE DESCRIPTION CGS

RD1845 HISTORY - 1954 SEE DESCRIPTION USGS

RD1845

RD1845 STATION DESCRIPTION

RD1845

RD1845'DESCRIBED BY COAST AND GEODETIC SURVEY 1941 (ANS)

RD1845'STATION IS ON THE SUMMIT OF MT. GAULDY, AND IS ABOUT 1-1/2 MILES

RD1845'W OF PAVED HIGHWAY 14, 4-1/2 MILES SSE OF HEBO AND 5 MILES NNW

RD1845'OF DOLPH. IT IS IN THE SIUSLAW NATIONAL FOREST. THE TOP OF THE

RD1845'TOWER WAS INTERSECTED.

RD1845'

RD1845'IN 1937 A DISK WAS CENTERED UNDER TOWER BY THE U.S.F.S.

RD1845'

RD1845'STATION WAS NOT VISITED IN 1941.

RD1845

RD1845 STATION RECOVERY (1954)

RD1845

RD1845'RECOVERY NOTE BY US GEOLOGICAL SURVEY 1954

RD1845'STATION WAS FOUND IN GOOD CONDITION BUT THE LOOKOUT TOWER HAS

RD1845'BEEN DESTROYED. THE STATION MARK MT GAULDY 1936 WAS NOT

RD1845'SEARCHED FOR.

 

As always – you guys are great – thanks for all the good assistance.

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...

We have found 3 fire lookout towers, each with a disk in the center underneath. We are having trouble figuring out what exactly a “Found” would consist of because we found the four tower foundation supports and the disk but the tower structure is gone.

 

For example, we found the disk and the 4 foundation supports for RD1845. I have copied the text below. In the 1954 description. It says the tower was destroyed but the station was found in good condition? Huh?

 

Can somebody explain that? Isn’t the center of the tower the “station”?

 

Before I log RD1845 I am trying to decide if I should call it destroyed because the tower structure is gone or call it found because we found the disk?

...

 

It appears that RD1845 was an intersection station, but that the geodetic position was transferred to the disk that the Forest Service plumbed underneath. So the geodetic position was preserved, but the tower was destroyed. If you found the Forest Service disk, you found the position, and can record its condition as poor, found, or destoyed (if the disk is now destroyed). The station (position) is still an intersection station, though, because the position was originally determined by intersecting the top of the tower.

 

It is of course possible that the original survey crew did do observations from the tower, in which case it may not be an intersection station. Only the field notes could tell you for sure.

Edited by holograph
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Just to be argumentative, suppose the original observations of a station were with a bilby tower over it and target lights on top, and and the ground mark also has an undeground mark.

 

Which is the station? In a manner of speaking the bilby tower was 'intersected' and occupied not the station mark on the ground.

 

Is the station destroyed when the tower was removed?

 

It all depends on how the observations were made. -OR- you could say there were all part of the station. It seems clear that the main thing that differentiates an intersection station from a 'real' or other 3rd order station is that it was not occupied. My point is the mere fact that the object described is a steeple, or a tower or a fire tower does not by itself mean it is an intersection station.

 

I would say that in many cases a disk set underneath a fire tower was probably set fairly closely and if it is marked as the station and still exists it is not destroyed. The target tower can move, be rebuilt and destroyed but the station may not still be there. And of course in many cases no such monument was set and nothing at the station was ever occupied.

 

The bingo post above exactly describes one such example, the tower was destroyed but the mark which is the station can still exist.

 

At any rate describing what you found seems to me to be important but I'm not keeping score.

 

One could assume something like the Washington Monument on the mall was an intersection station by it's nature, but no they occupied it!

Edited by jwahl
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How about commenting on my suggestion to look for a box score?

 

If it has one the point was occupied and is not an intersection station. If not, I think the station PROBABLY was an intersection station not occupied. Agree?

 

We've got a lot of clues and the only definitive one we sometimes can get hold of seems to be dashed lines on the official plots.

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How about commenting on my suggestion to look for a box score?

 

If it has one the point was occupied and is not an intersection station. If not, I think the station PROBABLY was an intersection station not occupied. Agree?

 

We've got a lot of clues and the only definitive one we sometimes can get hold of seems to be dashed lines on the official plots.

Not quite agreed. I've recovered many triangulation station, many with no reference marks (but some with "witness marks" such as tree blazes) or whose reference marks were not entered into the NGS database. Ditto no box store. Ditto third order. Practically all the US-Canadian boundary monuments are third order and no box score. But yes they were occupied triangulation stations (or traverse stations) and are not intersection stations.

 

Bottom line - you gotta dig deep. There is no simple formula.

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Not quite agreed. I've recovered many triangulation station, many with no reference marks (but some with "witness marks" such as tree blazes) or whose reference marks were not entered into the NGS database. Ditto no box store. Ditto third order. Practically all the US-Canadian boundary monuments are third order and no box score. But yes they were occupied triangulation stations (or traverse stations) and are not intersection stations.

 

Bottom line - you gotta dig deep. There is no simple formula.

 

Not only that, but the resurrected PD0674 Grand Manan station of the Eastern Oblique Arc appears on maps as an intersection station, but it is First Order!

 

So the rule is: there are no rules.

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So the rule is: there are no rules.

Keep in mind, too, that there IS an exception to every rule..

 

So there. :P

 

I dunno about anyone else, but I figure it this way - if it's not an object (disk, cross, rod, etc.) It's an intersection station. :lol: May not always be accurate, but 99% it works. That other 1% I enjoy trying to figure it out.

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Tilla:

 

Having read this thread, your log, and the description - I do believe this one simply to be an intersection - with a mention of the disc made for the sake of the history of the site.

 

Tower gone - intersection destroyed - however if it were me (and I did this with an airway beacon I found) I think simply posting a "note" would be the best move.

 

All that said - I could be wrong!

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Having read this thread, your log, and the description - I do believe this one simply to be an intersection - with a mention of the disc made for the sake of the history of the site.

 

I think simply posting a "note" would be the best move.

 

I agree with you. I edited the log to change the find to a "note".

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After reading the your log and the datasheets for both RD1845 and RD1844, I'm leaning in the other direction, towards calling it a find. Yes, the station was originally intersected at the top of the tower, but then its position was transferred to the ground when the Forest Service set the disk below the center of the tower. The fact that the Forest Service stamped LOT on the disk to me indicates that they were likely intending for the disk to mark the position originally intersected on the tower.

 

So to me, the question is whether the C&GS accepted the disk as an accurate re-marking of the position. The 1940 report on the RD1844 datasheet includes the statement that "NEW LOOKOUT TOWER HAS BEEN CONSTRUCTED ON SUMMIT, AND IN 1937 U.S.F.S. DISK WAS SET UNDER CENTER OF NEW TOWER, CONNECTED TO OLD STATION BY TRAVERSE." which makes it sound to me like the position of the disk was adequately checked and accepted.

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