Roche Point Bronze Plug.

[JDCAVE]

We discovered a bronze plug in a rock at Roche Point.





Does this mark a horizontal datum?

Jim

 

[rochepoint]

Must be one I lost........

 

[soin2la]

We discovered a bronze plug in a rock at Roche Point. Does this mark a horizontal datum?

Datum rarely dries and that appears to be several feet above the background water level, so I doubt it very much.

 

[JDCAVE]

So it’s a datum for tidal heights? It definitely looks to be bronze.

Jim

 

[HTurner]

We discovered a bronze plug in a rock at Roche Point.


Does this mark a horizontal datum?

Jim

Perhaps it is like this...?


https://www.cultofweird.com/science/ancient-screw-in-rock/

 

[HTurner]

Lol

 

[koliver]

Might be a survey monument.
https://maps.gov.bc.ca/ess/hm/mascot/
The MASCOT map shows 2 at Roche Point, one in the water, on on the land.

 

[soin2la]

So it’s a datum for tidal heights?

That one, as I said, is not likely Chart datum because Chart datum is selected so that the water level will:
- be so low that the water level will seldom fall below it
- not be so low as to cause the charted depths to be unrealistically shallow.

koliver with his MASCOT map could be onto something, as it could be the land based one is for some man made reason, while the underwater one, derived from the placement of the land one could be tidal.

Could the one you found be a horizontal datum for some land based structure? Yes. The CPR and BC Electric* established North Shore datum(s) in the early 1900s. It could possibly be related to the Second Narrows railway bridge. I could possibly be set there to generate conversations like this.

I’ll leave the rest of the digging to you. Please report your findings.

*An example:
North Arm.-Observations obtained in 1912; the tide gauge being placed at the Power Station of the B.C. Electric Railway Co. in the North Arm of Burrard inlet. Bench-mark; in a concrete pillar of the wharf at the south side of the slipway, being the eighth pillar from the south end of the wharf; the centre of a brass bolt set horizontally into the pillar at 9 inches from the face and 4 feet above the sloping surface of the slip, and just about High-water mark.

 

[JDCAVE]

Might be a survey monument.

https://maps.gov.bc.ca/ess/hm/mascot/

The MASCOT map shows 2 at Roche Point, one in the water, on on the land.

That certainly looks like it. The one in the water matches the location.

Jim