Help with Eccentrics

[TillaMurphs]

Yesterday we found the station mark and the 2 reference marks for RM1651 (woo hoo!).

 

However, we could not find the eccentrics (ECCs).

 

What can you tell me about eccentrics that might help us find the 2 eccentrics for RD1651?

 

As I understand it, eccentrics were sometimes used in cases where it was not practical to put a tripod above the station mark. Since the station mark here was on top of a large semi-pyramidal rock I can believe that could be the case.

 

Are there other reasons why eccentrics were used?

 

Any idea what we are looking for? A disk, a blaze in a tree, a pipe?? We looked in the area indicated by the box score and could not see anything obvious. Due to time constraints and the fact that we didn’t really know what to look for, we only did a cursory search for the ECCs on this trip.

 

Below are the box score and the history for RD1651 – Saddle Mountain. The eccentrics even have their own PID.

 

Is there any way to guess when the eccentrics might have been monumented? That might give us a hint as to how far we have to dig, etc.

 

Thanks for any help.

 

RD1651 HISTORY - Date Condition Recov. By

RD1651 HISTORY - 1935 MONUMENTED CGS

RD1651 HISTORY - 1941 GOOD CGS

RD1651 HISTORY - 1980 GOOD NGS

RD1651

RD1651

RD1651|-----------------------------------------------------------------------------------------|

RD1651| PID-------Reference Object------------------Distance--Geod. Az dddmmss|

RD1651| RD1653 SADDLE MTN RM 1 ___________ 3.918 METERS ____ 00320 |

RD1651| RD1633 HOFFMAN _________________ APPROX.28.4 KM ___0335918|

RD1651| ______ SADDLE MTN RM 2____________ 5.498 METERS____ 09956 |

RD1651| RD1654 SADDLE MTN ECC 2804_______ 17.758 METERS____ 24527 |

RD1651| RD1652 SADDLE MTN ECC 4704_______ 19.180 METERS____ 24733 |

RD1651|-----------------------------------------------------------------------------------------|

RD1651

[+jwahl]

An eccentric could be a target or a light sighted from other stations. I would check out if the 'lookout tree' or items setup on the tree.

 

ECC 4704 is 19.180 meters or 62.92 feet away in a SW'ly direction from the station. The description says that the sation is 63 feet NE of the lookout tree.

 

That seems like a pretty close match. The other eccentric is very nearly the same direction and about 4 feet different in distance. That seems consistent with two objects possibly on the tree or on the platform on the tree, or on opposite sides of the tree.

 

- jlw

Edited September 22, 2008 by jwahl

[+jwahl]

There are two sites for historic quads that I am aware of. I think they have the same maps though:

 

Maptech Historic Quads

 

This was the original source:

 

Univ. NH Historic Quads

 

- jlw

[TillaMurphs]

Hi Jlw,

 

Thank you for your reply. We found what we think is the stump of the former lookout tree and it is a ways away from where the box score puts the two eccentrics. At the box score location of the 2 eccentrics there is a tree that is about 15 years old and a lot of brush but no old trees or stumps. Everything is under tree cover.

[+m&h]

The only Eccentric mark we ever found was a disk. It is UT0565, SANKATY LH ECC 1979Details for Benchmark: UT0565, on a catwalk of the Sankaty Head Lighthouse on the east end of Nantucket. The Lighthouse itself was an intersection station (UT0553)Details for Benchmark:UT0553, but obviously no instrument could occupy it.

 

Several months ago,incidentally, we read news reports of the lighthouse's removal to a safer place, west of the eroding shoreline. So both marks were thereby destroyed, however intact they may appear. We haven't reported that to NGS, though we sent in a couple of the urls for the news reports, because we haven't revisited the site.

[+pgrig]

I believe that most ECC stations in this part of the country that I have come across are marked by physical objects or disks, and are described in the same way as "regular" stations. For example, I recently reported MY5140 as Destroyed and visited its nearby, quaintly-named "cousin", the Boulder West of Salem Turnpike, MY5128. I haven't reported on the boulder yet because it is so full of holes and iron rods that I couldn't positively identify the DH that is the mark. Guess I'll have to venture back out on the nearby golf course and risk getting beaned again...

[AZcachemeister]

 

RD1651| RD1654 SADDLE MTN ECC 2804_______ 17.758 METERS____ 24527 |

RD1651| RD1652 SADDLE MTN ECC 4704_______ 19.180 METERS____ 24733 |

 

If you search for those PIDs on the NGS site, and check the box to include destroyed marks you will find both of those are non-published due to 'No geodetic control at this mark'. This would seem to indicate, (as has been suggested) that these were temporary structures...probably set up to evade some obstruction of the actual station.

[NGS Surveyor]

I did a quick digital search of USC&GS Special Publication #247, “GEODETIC TRIANGULATION” and found many occurrences of the work “eccentric”. Here are some of the pertinent ones.

 

SP #247, page 86:

(f) The abbreviation “Ecc.” (for eccentric) should never be stamped on a disk. its use in the records should be solely to indicate that the observations made at that point must be reduced to the station center to close the triangles before being used in the subsequent computations.

 

SP #247, page 114:

ECCENTRIC STATIONS

Small eccentricities of the light plate are measured as described on page 100.

In cases where it will not be practicable to occupy the true station in the future

(see pp. 89 and 130), an eccentric station which is far enough from the center to allow

room for a separate monument should be marked with a reference mark.

Where the signal is built over an eccentric station marked by a reference mark,

all field computations are made for this occupied mark as though it were a new station.

A traverse connection is then made to the old station center mark. The horizontal

distance from the eccentric to the true station should be carefully measured in feet and

meters. Except for very short distances, standardized tapes, spring balances, and

tape thermometers should be used and inclination corrections determined; Horizontal

direction observations of an eccentric direction (at either eccentric or true station)

should be made and recorded in the same manner as for observations to reference marks.

(See p. 117 for description of station of an occupied reference mark and p. 184 for list

of geographic positions of an occupied reference mark.)

Directions to the azimuth mark should be observed at both the eccentric and true

station provided another station can be seen from both set-ups. If observations at

the true station are not possible, then, in addition to the observations on the azimuth

mark from the eccentric station, four positions should be measured of the directions at

the azimuth mark between the true and eccentric stations. If the true station and

azimuth mark cannot be made intervisible (because of construction, for example) an

additional azimuth mark should be established that will see both true and eccentric

stations. If it is no longer possible to use the true station (for example, if it is under a structure but not physically destroyed) observations to the azimuth mark may be made

only from the eccentric station if marked with a reference mark, and provided an appropriate

explanation is made in the record book and on the description of station card.

A sketch of each eccentricity is required in the record book and on the list of

directions.

 

SP #246, Page 117:

If a reference mark is occupied and its geographic position is computed in the field,

a new station description card on Form 525 should be furnished for this mark, and a

recovery note on Form 526 should be furnished for the station mark to which the Occupied mark refers. The word “eccentric” should not be used in the heading of the

description card or on a list of geographic positions in connection with the name of the

station or reference mark.

 

SP #247, Page 130:

The data in the heading are copied from Form 470. If the instrument is eccentric,

the name of the station should be followed by “(ecc.)” in the heading of this form. If a

reference mark is occupied instead of the center mark, and if it is planned to carry all

field computations through the occupied reference mark, with a traverse tie to the center

station mark, the notation “(ecc.)” should be omitted, and the name of the occupied

station in the top of the form will be that of the reference mark, such as “BALDY RM 2

1935.” The field volume number of the record book is recorded in the heading.

 

Page 129 has a sample sketch.

 

Page 139:

Eccentric signal lamps.-Except for four-foot stands, lightkeepers should show lights

from the signal as they find it, as long as the light plate is secured firmly in place. The

observer should be informed if the light is known to be eccentric.

It sometimes happens that the light from the station center is obstructed to the

observer, but if the light is moved a few feet to one side or the other, it can then be seen.

In this case, the light should be set up where it can be seen and the point marked

temporarily so as to remain identifiable. The observer is informed that the light is

eccentric and of its approximate distance and direction. Then when the station is

occupied the eccentric point is accurately measured.

 

See SP #247 on-line at: http://docs.lib.noaa.gov/rescue/cgs_specpu...o247rev1959.pdf

for more information.

 

GeorgeL

NGS

[TillaMurphs]

.

 

If you search for those PIDs on the NGS site, and check the box to include destroyed marks you will find both of those are non-published due to 'No geodetic control at this mark'.

AZcachemeister, thank you for the education.

 

I had previously pulled up the datasheets for those two eccentrics but when I saw the message at the top of the datasheet that said:

 

Elapsed Time = 00:00:00

Msg=FATAL_ERROR - No Marks found

I figured that the rest of the text was just boilerplate information. I never realized that the last line in the report actually said something important.

 

Now I know it is not worth another trip up there just to look or the eccentrics.

 

Thanks. Thanks.

 

I did a quick digital search of USC&GS Special Publication #247, “GEODETIC TRIANGULATION” and found many occurrences of the work “eccentric”. Here are some of the pertinent ones...

 

GeorgeL

George,

Thank you for the reference material to get me up to speed on eccentrics. Now, next time I run into an eccentric, this will arm me with information on how best to deal with it. What you provided is much more than I had been able to find previously. Thank you sir.

[Z15]

Here is the only example of Eccentric that I ever ran across.

 

A water tank was erected over another mark with the same name and no tower could be built over it. That mark is still there and called

SG0165 DESIGNATION - GAY MIGS 1934

 

SG0164'A 103-FOOT TOWER IS NECESSARY TO SEE ALL STATIONS.

SG0164'

SG0164'HEIGHT OF LIGHT ABOVE STATION MARK - 34 METERS.

SG0164

SG0164 STATION RECOVERY (1940)

SG0164

SG0164'RECOVERY NOTE BY COAST AND GEODETIC SURVEY 1940 (JHS)

SG0164'GAY ECCENTRIC HAS BEEN CHANGED TO GAY 2. THE STATION MARK

SG0164'AND REFERENCE MARKS NO. 0 AND NO. 1 WERE STAMPED GAY, 1939

SG0164'ECC. THE INSCRIPTIONS ON THESE MARKS WERE CHANGED TO GAY

SG0164'2, 1939. THE AZIMUTH MARK WILL BE SIMILARLY CHANGED AT

SG0164'A LATER DATE.

SG0164

SG0164 STATION RECOVERY (1945)

SG0164

SG0164'RECOVERY NOTE BY US GEOLOGICAL SURVEY 1945

SG0164'MR. W.W. WIITALA, A MEMBER OF THE U.S. GEOLOGICAL SURVEY,

SG0164'LOCATED AT THE COLLEGE, WHO IS FAMILIAR WITH THE WORK DONE

SG0164'THERE IN 1939, WAS REQUESTED TO MEASURE THE DISTANCES BETWEEN

SG0164'GAY (MICH. GEOD. SURVEY, 1934) AND GAY 2, 1939.

SG0164

SG0164 STATION RECOVERY (1977)

SG0164

SG0164'RECOVERY NOTE BY NATIONAL GEODETIC SURVEY 1977 (WOM)

SG0164'GAY 2 1939 WAS FOUND WITH THE SURFACE MARK LEANING AT ABOUT A 20

SG0164'DEGREE ANGLE. THE UNDERGROUND MARK SHOULD BE IN GOOD

SG0164'CONDITION. GAY MICH, GEOD. S 1934 WAS RECOVERED IN GOOD CONDITION

SG0164'AS WAS REFERENCE MARK 1. THE AZIMUTH MARK WAS NOT RECOVERED.

 

Edited October 2, 2008 by Z15

[+Black Dog Trackers]

I looked in the 2006 state .dat files. There are 872 PIDs with ECC in their name.

Here is part of the list, looking around the middle of it:

=====================================

NJ.TXT: JU2662 DESIGNATION - GOWDYS HOUSE ECCENTRIC

NJ.TXT: JU2665 DESIGNATION - LOVELADIES ECC

NJ.TXT: JU3041 DESIGNATION - HILL RM 2=ECC

NJ.TXT: JU3117 DESIGNATION - NEWTON ECCENTRIC

NJ.TXT: JU4102 DESIGNATION - RUM ECC

NJ.TXT: KU3877 DESIGNATION - EASTMAN ECCENTRIC

NJ.TXT: KV3552 DESIGNATION - SANDY HOOK LIGHTHOUSE ECC

NJ.TXT: KV4036 DESIGNATION - WEEHAWKEN ECC 1933

NJ.TXT: KV4249 DESIGNATION - TRUST ECC 1933

NJ.TXT: KV4730 DESIGNATION - ELIZABETH ECC 2

NJ.TXT: KV4784 DESIGNATION - NEWARK ECC 1933

NJ.TXT: KV4787 DESIGNATION - ELIZABETH ECC 1933

NJ.TXT: KV4916 DESIGNATION - LEONARDO PIER REAR RANGE ECC

NJ.TXT: KV5170 DESIGNATION - TOWER E ECC

NJ.TXT: KV5175 DESIGNATION - TOWER G ECC

NJ.TXT: KV5497 DESIGNATION - NJ 156 ECC

NJ.TXT: KV5633 DESIGNATION - CAR ECC

NJ.TXT: KV5674 DESIGNATION - TULL ECC

NJ.TXT: KV5727 DESIGNATION - KERR ECC

NJ.TXT: KV6947 DESIGNATION - NJ 156 ECC RM 1

=====================================