Two disks at one location?

[skydiver]

I know there are some surveyors that frequent this forum, so maybe one of them can answer this question.

Why did I find TWO essentially identical benchmarks at this location?

 

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Friends don't let friends NOT geocache.

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[+Dawgies]

The one with the arrow on it is an Azimuth(?) marker. A marker pointing to the direction of the Triangulation marker. There normally seems to be two or more of these that help to pin point the exact location of the main Triangulation marker.

 

~Honest Value Never Fails~

[+Dawgies]

The one with the arrow on it is an Azimuth(?) marker. A marker pointing to the direction of the Triangulation marker. There normally seems to be two or more of these that help to pin point the exact location of the main Triangulation marker.

 

~Honest Value Never Fails~

[+Dawgies]

If you check the original data sheet it states that there are reference points around the Triangulation disk in the outcropping bedrock.

 

 

~Honest Value Never Fails~

[+Dawgies]

If you check the original data sheet it states that there are reference points around the Triangulation disk in the outcropping bedrock.

 

 

~Honest Value Never Fails~

[skydiver]

Yup, looks like your right, which means there's at least one more reference mark up there somewhere. I might have to go back and find it now.

 

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Friends don't let friends NOT geocache.

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[skydiver]

Yup, looks like your right, which means there's at least one more reference mark up there somewhere. I might have to go back and find it now.

 

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Friends don't let friends NOT geocache.

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[+OzzieSan]

On the original datasheet you will find this info.

 

RY0845|---------------------------------------------------------------------|

RY0845| PID Reference Object Distance Geod. Az |

RY0845| dddmmss.s |

RY0845| RY0844 MISSOULA SUGAR FACTORY STACK APPROX.13.2 KM 0811129.7 |

RY0845| RX0995 MISSOULA COUNTY CTHSE DOME APPROX.16.1 KM 0882936.6 |

RY0845| RX0994 MISSOULA MONTANA POWER CO STK APPROX.16.2 KM 0900744.6 |

RY0845| BLACK MOUNTAIN RM 2 12.538 METERS 16231 |

RY0845| BLACK MOUNTAIN RM 1 9.242 METERS 28217 |

RY0845| RY0856 PETTY APPROX.15.9 KM 2870137.4 |

RY0845|---------------------------------------------------------------------|

 

You have found RM2 so using this info should help you find RM1. If I recall from my hunts RM2 should be about 12.538 METERS @162ish degrees from the BM. RM1 should be about 9.242 METERS @282ish degrees. Unless I have it confused with something else.

[+Kewaneh & Shark]

It is a common practice in surveying to use something called swing ties to locate a monument. On a smaller scale, they may be as simple as a couple of nails driven into the ground at cardinal directions 2-5 feet away, and are used to help locate the main monument. This is done a lot around here when the monument is in the middle of a road and buried under asphalt - the nails can be used to 'swing' to the monument's proper location.

 

Of the two caps you found, the cap in the photo labeled Mark #1 is the actual triangulation mark that you were looking for. The cap in the photo labeled Mark #2 is a local reference monument (or swing tie, of sorts) showing the name of the triangulation monument and its direction, the reference monument's number, and the date it was set. Because this is labeled 'NO.2.' it can be assumed that there is a 'NO.1.' somewhere. Also, the 1934 CGS description mentions "REFERENCE MARKS ARE STANDARD BRONZE DISKS WEDGED IN DRILL HOLES IN OUTCROPPING BEDROCK." If you went back and spent a few minutes looking, you'd probably find at least one more reference monument. (According to the original data sheet, 'NO.1.' is even closer than 'NO.2.')

 

Keep on Caching!

- Kewaneh