Ever notice how you can shoot some monuments and so can 10 other people and they will all come up with different results?
I am of the opinion that it is impossible to take any measurement without a certain degree of error.
Remember the old days as an eyeman when you had that old crew breathing down your neck while you were rapping angles with the good old T2? There were times when I would rap 10 different sets because the mean closure was not good enough.
Fortunately I was honest. I used to be so good with these angles that I could give a false reading so the crew chief would move along. It's all simple math when you think about it.
Which brings me to the point of all of this.
Today's newbies have zero clue what it really means to measure. They will never know a chain for what it really is, they will most likely never rap angles and most likely never run 3 wire levels. Yes there are some exceptions depending on where they work and what they are doing.
So my questions is what will became of the basic fundamentals of survey measurements?
Is the robot or total station more accurate than the GPS? I think absolutely in verticals. Horizontal who knows? I will tell you that I often use steady sticks with the gps, especially when obtaining control and I let it cook a little longer, at least 30 senconds.
There was a time in my life when all we did was run level loops all day long. Yes that's right youngsters loops.
The guy that I spoke about a couple of posts back Howie went to some on site welders and had them make these turn plates that were made of 3/8" steel with bolts in the top and those were the turn plates that we toted from station to station and then back again and again. They had 3 angled legs, were 6 inches tall and then the bolt and were about a foot by a foot and we would drop them and then stomp them in. They weight about 20 pounds each.
We ran some tight stuff and if we checked in over 5 thousandths we did it again. Why? I'm not sure.
I am wondering if the newbies know how to read a rod to the thousandth or if they even know to rock the rod? I'm sure some do.
When I was with Howie he made us use a calibrated deluxe rod bubble and only a 2 section wood rod.
I am wondering how many know how to run levels up and down hills and keep the turns balanced?
Simple. You and the rod man stay exactly 100 feet apart and parallel on the slope and work your way up and down.
Anyone pre 90's probably knows this.
I find it amazing that different companies can shoot the same section with the same character in monuments and come up with significant different results. Tenths, not hundreths. I actually think part of it may be an incorrect grid to ground scale factor. But who knows. It could just be a case of lazy head up ass.
So what is actually happening to measurements? Are they improving though technology or getting worse from button pushers that have zero idea of the basics?
It's a good question.
What say you??
Make it a great week surveyors.
Hi John, Can’t help myself, so here goes. There are inherent errors in every measurement in my opinion. I was once told in a seminar I attended that that there are 8 probable errors in every instrument reading or measurement. Wrapping angles and shooting both direct and reverse removes 7 of those errors. We used to wrap 6 angles for ADOT work back in the early 80’s and only 4 sets for the day in and day out stuff. Going by memory here, if your mean was within 10 seconds my party chief would call that good enough, but you’d have to check with him. As far as GPS control – all points, unless you are going to die in a dangerous intersection, 90 seconds minimum.
ReplyDeleteAs far as level loops go, we either used a Philly (Philadelphia) Rod or a Chicago Rod. We also always made sure when extended, we had exactly 1 foot above and below the joint (s). In the old days (if you will) we never ran a level loop with a fiberglass rod. We ran 3 wire loops more times than not. Easier to isolate a bust.
Ask your pimply faced pasty fuck instrument man how far away you are when running levels... Stadia anyone?...
As far as accuracy between GPS, Conventional Instruments, and Robots... Knowing your equipment is key – and their limitations...I find that paying very close attention to your satellite geometry always pays off. That damn yellow box will lie to you. “Fixed, and plus or minus 0.02’ – ya ... NOT. That said, when you stay within reasonable limits, I find my Robot to be amazingly accurate. That darn thing knows where the center of the prism is. “All things being calibrated properly". – That also being said, I have an amazing instrument man that runs an extremely tight instrument and are traverses, including verticals, always seem to impress me... and I’m old.
Just remember, go out and measure something in August when it’s 120° in the shade – then go out and measure it again in January... I’ll by the beer if you hit “flat”...
CORRECTION: and OUR traverses
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