So I have just started my career in surveying as an instrument operator and I am still struggling to understand when you would use a Philly rod vs a linker rod as the linker rod seems much easier to use.
It is a Lenker rod, not linker. I didn't even know that they are still in use but they were most commonly used on construction staking decades ago when I was an IM. The Lenker rod gives you a direct reading when it's set from a BM with a known elevation without adding and subtracting your level's HI, back sight and foresight and adding or subtracting the +/- observations but it's easy to drop 10' if you are not paying attention. It's great if you are working on staking a job to quickly calculate cuts and fills.
The Philadelphia rod is the best to use for bench runs to and from a BM for a check on the return to the BM because you can rock the rod to find the correct rod reading when it hits it's lowest mark on the rock. The Philly rod is a general term for a two section rod with a thumb screw clamp to hold the extended portion in place but it can slip, that's why it's always critical to measure between the two even foot marks closest to the clamp. There is also A Chicago rod that has two extensions.
These are all great tool to learn differential leveling from but are not in common practice these days.
Short answer: A linker rod is a direct reading elevation rod. The linker rod has an adjustable scale that can be SET to a known or assumed elevation on any given ‘benchmark or point of assumed elevation’, and thereafter all ongoing readings will be relevant to that BM and can be read directly from the rod without having to calculate the ‘difference’ in readings as I will try to briefly explain next.
A Philly Rod, is not adjustable and requires a ‘plus’ elevation on a benchmark or other point of reference in order to set a ‘height of instrument’ (aka HI), then all subsequent readings will be a minus (measure down) or minus from that HI.
Again, this is a “short answer”: linkers are GREAT for vertical measurements within a few hundredths of a foot (huns).
A Philly Rod is much more appropriate if you are attempting to measure to a better accuracy than that achievable with a Linker Rod.
All that being said, it is a traditional ‘beer challenge’ if the rodman can set the correct reading on the linker rod on his first attempt. If he does this the IO (instrument reader or Party Chief) owes him a beer.
I agree with Chris. To restate, the Lenker is for high production but limited precision. When you have to put elevations on a a lot of hubs from a single setup, but they don't need to be super precise (such as when setting out curb stakes, for example) the Lenker is a handy tool. When you want to transfer elevations with greater precision, such as when benchmark levelling, the Philly is a better tool.
I must say that the last time I saw a Lenker Rod in actual service was the mid 1990's, and it was rather old tech then.
So yes, the correct name is indeed ‘Lenker’. Thank you Chris.! The other replies above are correct with the exception of their indication of these rods being antiquated beyond current use. There are many instances where the ‘Lenker’ rod is still relevant and will ‘pay for it’s self’. In my region, flooding is a constant concern and therefore both residential and commercial structures are designed with a ‘finished floor elevation’ that is relevant to the surrounding street and drainage improvements. In a residential subdivision, a Lenker Rod can be used to measure multiple ‘finished floors’ or preferably ‘form boards’ (allowing for corrections before pouring), just as quickly as the rodman can walk them. Again, the conversation can go deeper, but it is time for this “Early Bird” to catch some Z’s.
@mark-mayer Amen!
@cv in the modern world a Total Station can do what you talk about as quickly and easily as setting up a level with reduced elevations provided in real time showing on your DC, as well as the cut and fill. Don't get me wrong, I believe that old school methods should be taught but Lenker and Philly rods for common usage went out the door two or three decades ago.
The first thing you have to learn is that the Lenker rod reads with the numbers increasing down the rod and the Philly rod reads with the numbers increasing up the rod.
My one & only time using a Lenker rod was to put elevation on numerous traverse points around a project site in the bad part of Memphis. The PLS wanted everyone to know the proper operation of the Lenker rod. Once we got a rhythm down, everything seemed to go quickly. Needless to say, but we busted the levels several times by 10' when checking into the traverse points and wound up running bench levels through each control point before we started collecting data.
Never used it once in 35 years of surveying. Used the Philly rod a lot years ago. But now, hardly ever break out the 25' Crane rod, unless I need it for some high (meaning low) topo shots
As I read the old text books, it seems that Philadelphia, Chicago,, Detroit, etc. refer to the way the scale is marked, rather than the construction of the rod sections.
There are several ways to indicate the subdivisions of the scale, of which Philly seems to be most common.
I would have to pull it out to be sure, but I think the beat-up Lenker a guy gave me has an upside down Philly scale.
RE: When to use a Philly Rod vs a Linker Rod?
In the 1960s...
Looking at a __.__
Need a__.__
A beer for setting the lenker correctly the first try? My old company owes me a couple kegs!
We would set all the hubs for the day horizontally, then break out the level and lenker rod to get elevations. Then calc cuts and fills and write up lathe.
One of my favorite tools back then because it got me home quicker.
A Lenker Rod keeps the field crew from having to add or subtract once the party chief gets the rod set. With a robot and GNSS, I have not had to add or subtract in twenty years.
I see that new Lenker Rods can be purchased on Amazon - as accessories to laser levels for construction.
My first day surveying, August 11, 1975, we used a Lenker Rod, and then for several weeks after that. Then one day we got out the Philly; and I was like, what's this, why would you want to do all that math?
About 10 years later, I went to work for Peter Kiewit Sons; they exclusively used the Lenker, but they set it on the footing or grade beam and set 0 (X) and went up or down what ever the plan said.
Back in the day, we kept horizontal and vertical separate. Today, we enjoy the best of both worlds. Just like everything we do; it's all about procedure. I can be as accurate as I want, with every tool I use, as long as I use best procedure.
Today, everyone is using their robot or total station; just make sure you check a known elevation and you're golden.
A Lenker rod was used for doing topography on big flat areas. I used it to grade parking lots and sports fields. It was direct reading.
A Philadelphia rod had an upside down scale on the back. If you inverted the rod on the shot you could read it as a check of the first reading. (If I am remembering correctly.) How it worked on a Lenker rod is interesting as the scales rolled around the rod to set an elevation.
Back in the day, we kept horizontal and vertical separate. Today, we enjoy the best of both worlds. Just like everything we do; it's all about procedure. I can be as accurate as I want, with every tool I use, as long as I use best procedure.
Amen. Don't force the job to fit the procedure, build the procedure to fit the job.
The key point has been discussed already accuracy vs speed in terms of the work being performed.
Since you are asking the question, then you may well be working somewhere that those are still the tools available and in place (while less common than in the past, they are still in use at some places).
One of my early jobs, my boss came out to train me in the proper use of the Lenker because I hadn't used it, but we (crew) had already set points and were grading with a Philly rod by the time he arrived. When he saw the check procedure and speed things were going, he just said continue with the Philly, so I'm not sure just how much faster the Lenker would be. It wasn't too long after that I was able to convince them we could grade with the total station and prism (mid-90s - so 30 years ago, which gives an idea of why folks are commenting on the use of these leveling rods being a bit outdated).
oh my. Lenker aka elevation rod. I don’t know why its said to not be as precise as a philly rod. They came in the same graduations tenths and hundredths of a foot. I have set so many bluetops with those its not funny. Graded a lot of curb and gutter stakes also.
OP most have covered everything here. When grading for vertical with a philly rod or level rod aka fiberglass rod one would read off the site BM then compute the HI then the grades as far as one could go could be computed and then a rod reading could be computed for the vertical. Now when you get on a hub and read the level rod again you could figure the cut or fill from design grade vs the difference in rod readings. The elevation rod or Stinking Lenker rod you read or set the rod on the elevation BM etc. so now it’s elevation on every hub and the difference of design. So before data collectors we would take a set of plans and compute the vertical grades along the design slope or vertical curve at horizontal stations. We would have these elevations pre computed or as we went along. We would have laid out or staked out the horizontal position and offset. Then we would get the level out to grade everything. The lenker was just a masterpiece of helping reduce extra steps in math and blunders of writing all this stuff in a field book. We did keep the field book with lenker it was just less writing. And helped us be more productive. But as ChrisB said you could get in trouble real quickly on terrain changes in vertical. In the TN area we were elevations of say 200.00 ft so say the bm was 210.50. We would slide the tape to read 10.50 as an example. Out west it was elevation of say 5000.00 ft so bm at 5010.50 we would still set tape on lenker at 10.50. There were checks made as it was not uncommon for i man to read rod and tell rodman he was good. Rodman didn’t lock the tape down so nothing was good. So you would shuck the rod like a pump shotgun sorta and rodman would give extra reading on the bm. To check the reading. You can run levels with lenker but not as intuitive as running a whole level line with regular level rod philly or other. So above they are correct setting grades on construction site for vertical is what the lenker rod was for also known as elevation rod. Glad you are asking thats how you learn and knowledge is power. If used for good.