Yesterday, I came across a gps base, set up on the side of the road. I have a RR spike, or such buried within 10' of it, for my GPS base. This is the 14th time I've come across this.
It's a good idea to briefly search an area where you plan to put your base, to see if there's already some sort of controll point there.
Also, I have set my base before, on my nail, NOT REALIZING that it was very close to an existing survey corner. Then, another surveyor found and USED my GPS base spike as the property corner!
We all are creatures of habit. The same habit! At some point we can "collide".
Shonstedt is your friend.
Thank you
Nate
I always try to do a cursory check for existing control or property monumentation prior to establishing new point for both conventional and GNSS.?ÿ I would not say I go to the effort of breaking out the pin finder to scan for someone's 60d nail but I look around.?ÿ If I find one that works and fits my needs, I'll use it.?ÿ Not that I'll use their coordinates, It just makes it easier to find the correct one in the future.
Also, my control and property monuments are very different.?ÿ Being from the land of recoding states, all of my property monuments have either my company name or my name & PLS number depending on state requirements.?ÿ My semi-permanent control monuments, those intended for use by other or over a long period of time, are tagged as control along with my company name.?ÿ The rest are just small mag nails, hubs, scribes or box nails.
In the early days of GPS I set a rebar near an access road, 150' or so off a lonely county road. Then a couple of years later I went out, found my rebar almost immediately and started surveying, only nothing checked. Yep it was a different control point, mine was 10' or so east. Someone else had decided that was a great place for a GPS point. Wasted a hour or so. The good GPS set-up places tend to attract surveyors.?ÿ
Sooooo, now I make sure it's identified some way but you have to be careful. I had an extensive photo-id job for a large mapping project, because photo-id points at fence corners had been used as property corners before, so I set an aluminum cap on a rebar and stamped "control point not a property corner". Still it got used as a property corner a few years later. It is still there I think and the stamping is as clear as can be last time I looked.
I started to identify the points I use with a location: Lot#, Section #, Township#, Range#. So the point can be CP 852235. That puts it in Lot 8 (SE4NE4) section 5, township 22, range 35. Using the standard numbers for 16 quarters in a section. 16362235 would put that control point in the SE4SE4 section 36, T22, R35. Since you end up reoccupying these points over and over it gets put into many different jobs and GPS being GPS there are few times you need more than one base point per 40 acres.?ÿ
My favorite is a mag nail in rock about 2 feet east of an NGS tablet. I was on a hike without my camera. Next time in the tablet was gone but the mag was still there...
Pulled up to a job one time to run some levels. Had the plans with BM description in my hand. Jumped out of the truck and the "crew chief" that was working with my crew that day took off across the street. Low and behold he found a chiseled square on the inlet. He says, "we can use this one!". Excited like he had saved the day.?ÿ
Too bad the BM he found wasn't the one shown on the plans. I calmly asked him some questions about the BM he found to verify that we could use it. Needless to say, we used the one shown on the plans.
I set Bernsten brass plugs in concrete sidewalks for control on building projects that I return to many times over a couple of years. I can't say how many times I've returned to find a fresh MAG nail in a sidewalk crack nearby.?ÿ
As far as GPS bases go, I'd encourage one and all to find a place for the base that is not at the side of the road.?ÿ ?ÿPrimarily for the safety and security of your base, but also because every time a truck passes by it is going to block out satellites, or at least cause multipath. Church grounds and cemeteries are favorite places for me.?ÿ Schoolyards in summer and parks in winter work as well.?ÿ
Speaking of colliding surveyors... Boundary work was being done on a parcel that was adjacent to another undergoing construction. The first parcel's crew was setting a mag nail on an extension of a boundary line while the second parcel's crew was shooting topo with their robot set up on their control point nail, about a foot away.
Mostly, these are off near the r/w fence. For hill bullies, that's "by the road"
While I??m all for continuity for a project; I??ve changed my methodology quite a bit in the last year. Gone are the days of setting control points for boundary work. Too often do I have to move my base because of the terrain. In my area where there could be hundreds of feet in vertical relief over short distances; I must move around the section re setting my local base.?ÿ
Every project is on SPC and can tie into any other project, and I did away with setting points in the ground. I simply setup, get on the network, shoot a base point RTK with multiple observations over 5-10 minutes worth of data then switch the unit over to a local base. (Local but still on SPC) I??m rocking and rolling in radio in less than 10 minutes and it??s off again to tie in / check and measure. It??s my virtual ?ÿpoint in space. And there??s very little centering error because I never move the unit once it??s been setup for the initial grid measurement.?ÿ
Also, there??s never a need to use the same point because every shot is relative to the other. Like I said it??s all on SPC.
Happy hunting.?ÿ
Dave
Can not count the times my helpers have set up on the wrong control because they did not check any of the accessories in place.
It only takes a few minutes to check to make sure it is the correct point.
Happens all the time.
0.02
This is also why you can't believe everything on the newest corner record available.?ÿ Investigate, people.?ÿ Investigate.?ÿ Do proper research.?ÿ Please.?ÿ Corner records only go back a certain number of years.?ÿ Dig deeper in the records so you dig in the right places in the field.
A pet peeve is pulling up to a corner with corner record in hand showing three to five reference ties to items that are still precisely where they were X number of years ago.?ÿ Meanwhile, Joe Quickydicky, was there recently and added another three to five references, most of which can be confused with being the ones already there.?ÿ Example:?ÿ MAG nail set in power pole 33.1' NE.?ÿ Find that one and another MAG nail in the same power pole but about 90 degrees from the first at 33.7' NE.?ÿ Why?
What should I do?
It's the perfect little spot for a base. Little hill, and all. I go to set up, and there's ALREADY a nice mag hub nail there. It's sticking up a little, out of the grass.
A. ) Set up on it and use it as is.
B.) Set up on it, dig depression, and use the plummet to lower it a few inches, and pack it in properly.
C.) Set up on it, dig the area out, and change the kind of nail, ie fd mag hub, set R/R spa with drill hole in top, or bridge spike with hole in top.
D.) Move over and do my own thing, setting a dis-similar type of Mark, reference the found one, and don't disturb the other guys mag hub. Even though a mower, or cow can disturb it easily.
F.) ?
?ÿ
D. On the grounds that I like to set something more substantial than a MAG Spike for a base control point. If the first surveyor had set a 1/2" capped iron rod I'd go with A.
B & C would be dirty tricks to play on some other surveyor.
This is a true story, although even I find it hard to believe that it actually happened.
Back around 1990 or so I was doing a large GPS bluebook project for an urban county in south Florida. Many of the stations were existing section corners, while others were just random control stations. All were set/recovered by the county surveyor. I think all of them were existing stations that had been used for years, so they weren't set with GPS in mind, although most were in the open, often in the middle of a road intersection. We had to do a few eccentric stations, which means that we would set a new point in the open (rebar) and then the county surveyor would do the conventional tie to the section corner or monument nearby.?ÿ
The time of year was winter, so back then the satellite constellation was best at night. I think we had 4 or 5 guys and all of the sessions were carefully scheduled, there were no CORS or HARN, just a couple hundred new stations and a dozen or so existing NGS triangulation stations to tie into.?ÿ
So each night before we left each guy would get a sheet with the station names, descriptions, and times. No cell phones back then, and we were too far apart for radios. So it was critical that instructions be followed. If a guy got lost, or started too late, that would have to be redone. We had to use paper maps at the time, no Garmin's or in vehicle nav systems.?ÿ
I sent one guy who wasn't particularly smart (career rodman, if you know what I mean) to an eccentric station. He got there, couldn't find it even though it had several reference distances to the curb, etc, so he assumed it had never been set. So he set a new rebar. Next morning he tells me he set a new station. I could not believe it. So I went out there, and he had set a new rebar 0.15 feet away from another rebar, both flush. They were practically touching each other.?ÿ
The same guy had on several other occasions occupied reference marks at triangulation stations rather than the actual station itself.?ÿ
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