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What's this marker?

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A couple of years ago I found this marker on the former experimental rocket base on the far eastern tip of Michigan's Keweenaw Peninsula:


It's a stake, possibly aluminum, driven into a large chunk of rock (part of the coastline, definitely not moving in this geological epoch). It had blue paint around it (you can see in the photo). A few feet away also in blue paint was written "GPS 150" as you see here:



Anybody know what this is? It's on property previously used for sounding rocket research so may have had some US government use in the past.


The timestamp on the first picture is 2000/07/30 18:07:55 - I wish I had been taking pictures of my benchmark finds in the past - I have some going back 15 years but didn't really record them carefully; it would be fun to go in here and predate the WWW on my logged finds!

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I would agree with Boundsgoer. PK Nails are commonly used as temporary points for surveyors. I use them often. They are simply a hardened steel nail with rifling and a sharp point, which make them easy (easier) to put in hard surfaces such as asphalt, concrete, or rock. They are usually only an inch or two long. A dimple in the middle of the top makes it easy to center to survey rod. Cotton spindles are also commonly used for the same purpose.


The 'GPS 150' marking indicates that it may have been part of a GPS survey network.


Keep on Caching!

- Kewaneh

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I have logged quite a number of stations designated GPS XXX (e.g.

GSP 125 in Fairfax County, VA.) I tried searching the NGS database to find a station name in Michigan beginning with 'GPS', but it came back with no hits. It might be part of a county network or, as others have suggested, might have been privately placed.

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Right on, that's a PK (Parker-Kalon) masonary nail. You can buy them at most hardware stores. They come in various sizes. We used them alot in highway construction surveing but another brand is on the market called MAG nail. They are more magnetic than PK's.

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