I set a GPS control point in 2010, in a remote part of my county in NW Colorado, where there is no cell phone or network. I always look out for snow plows, which run about 6 months a year. I assume that most plows do not target street signs, so I hid this puppy near the street sign. This year, my heart sank when I saw a little divot at the base of the street sign. May she rest in peace.?ÿ
sniff. funeral dirge....
Set a control point in a large concrete slab that provided hope for decades of accessibility. ?ÿNope! Less than two years.
Recently had an RP mon set by our headquarters GeoMetrix crew in a county road gravel shoulder, for a section corner that will no longer be readily accessible due to roundabout construction... local water district installs a water line in that same shoulder about two months later. FORTUNATELY, the surveyor on that project contacted me about it and I told him just to reset it reasonably nearby where we had originally set it; we hadn't done the observations yet so no big deal. Definitely the exception to the rule, so to speak.
Thing is, the designer for the roundabout knew about this water line project but failed to mention anything to me regarding it... GRRRRR.
The only superior evidence is that which you haven't yet found.
I'm working on the extension of a large port project I did 2 or 3 years ago.?ÿ I set nice 3" mag nails with washers at six locations.?ÿ This is not an area that I would suspect gets much if any snow plowing.?ÿ I returned this month to find holes in the asphalt at four of the six points.?ÿ Fortunately the iron rods I set are still in place.
For the last several years I have started setting Berntsen copper plugs for primary control in asphalt.
Looks like it put up a good fight and didn't come out easy.
N10,000, E7,000, Z100.00
PLS - IL, MO, AR, KS, MN, KY
In most of the areas I have done extensive bench mark recoveries I've found 1/10 to 1/4 remaining from 1934/35.
A great many of those remaining are too close to an active railroad for easy use.
To John Putnam,
I have noticed that MAG nails set in areas exposed to salt water can?ÿcorrode fairly quickly.?ÿ I have found numerous "holes" with magnetic debris.
Have also found shanks with the head corroded off, and recently picked a corroded mag nail out of the pavement with my fingers. The shank was about the diameter of a roofing nail.?ÿ This was about 600' from the water.
Bob Freeman
Bob,
This site is about 40 miles up the Columbia River.?ÿ In this case I think they are using a grader to clean the roadways and laydown areas of dirt and debris.?ÿ The holes are really big now. ?ÿ
Sorry about the blinders.?ÿ I saw "port" and didn't think outside of my own neighborhood.
So then you are talking about dissimilar metals corrosion. I think that is a lot faster acting.
When I set mag nails in asphalt I like to use the 6 lb. hammer and finish with a couple of roundhouse swings to hide them from the snowplows.
Slight hijack - Last week I went out to extend some old control.?ÿ The existing points were 6" mag-hubs set in 2015; not very old at all.?ÿ The only way I could recover them was via the swing ties that the conscientious I-man (as in I) took back then.?ÿ They did not sing at all to the metal detector until I jacked the sensitivity way up and got within an inch of them.?ÿ ?ÿNothing odd about the location or soil type.
Last week I recovered some control from 2004 that consisted of 20D nails.?ÿ These rang like crazy even through a 2' snowbank and 6" of gravel shoulder.
Now I just bought a box of 6" Mag-hubs not long ago and it cost me over $100 for about 362 of them.?ÿ Pretty pricey for something that doesn't perform as advertised.?ÿ If they didn't have that cute little dimple I wouldn't have bought 'em.
Been using galvanized 60d nails for close to 8yrs.
Rarely set anything in roads unless it is absolutely necessary.
Reference rods on or around the margins satisfies the client and keeps potholes from forming.
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When I set mag nails in asphalt I like to use the 6 lb. hammer and finish with a couple of roundhouse swings to hide them from the snowplows.
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I think banging extra hard on mag nails de-magnetizes them.
We drill a pilot hole (1/4" for a 3/8" nail) and countersink the asphalt by chiseling out about 1/4" of asphalt.
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When I set mag nails in asphalt I like to use the 6 lb. hammer and finish with a couple of roundhouse swings to hide them from the snowplows.
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I think banging extra hard on mag nails de-magnetizes them.
We drill a pilot hole (1/4" for a 3/8" nail) and countersink the asphalt by chiseling out about 1/4" of asphalt.
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Use a magnet lot less fuss
A long time ago, there were some mons on a construction site I was working that SHOULD have been well out of danger. Still, I pointed them out to the super and said to make sure to save them (as in don't disturb them).
A couple of weeks later the super pointed to the back of his truck. "Hey, I saved those survey markers for you."
I learned to be careful about what I say, even if it seemed obvious. (And also, never to count on a mon to remain undisturbed even if it's "outside" of the work zone).
I set 1/2" x 24" or longer rods with plastic caps for control in dirt or gravel and Bernsten plugs in concrete. Occasionally I will set 6" mag spikes in asphalt (drilled holes) if the asphalt is sound.?ÿ When I set a hub & tack, mag nail, or 60d spike, and I sometimes do,?ÿ I consider the point to be temporary.?ÿ My control goes in well outside the work zone and I resect convenient instrument positions to work from.
A pet peeve of mine is mag nails set in sidewalk cracks or alligatored asphalt that someone is trying to pass off as "control".?ÿ?ÿ
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The old surveyors saying:
When you go hunting, take a surveying stake, if you get lost drive it into the ground and hitch a ride with the blade operator who shows to blade it out.