Pros: 25' of total length a very useful piece of survey equipment
Cons: compartments can retain water and numbers will fade over time.
The level rod differs from the Linker rod in both capability and usability, but functionally the rods are comparative. In this review I will compare and contrast both pieces of equipment and explain how they not only work, but the different capabilities for each. Within the realm of surveying there are several types of grading or measuring rods for the purpose of carrying an elevation. Within in surveying is coordinate geometry, which is known as X, Y, and Z where Z is vertical. So for the sake of our review we will be talking about this particular Level rod and how it works and comparing it to my previous reviews of its counterpart the Linker Rod.
The 6 Section Fiberglass Level Rod is a Fiberglass rod which is both strong and flexible. Each section of the rod covers about 4 feet of splay so it expands to 25 feet at the maximum height. The sections lock into place using a solid plastic button. Overall the rod is built to withstand different climate temperatures, field conditions, and everyday construction environment usage. I’ve found that we’ve had the same rod for several years and only require minor lubrication and cleaning of the locking components to maintain the rods integrity and usability.
The first thing you’ll notice about the 6 Section Fiberglass Level Rod is it comprised of six four foot sections that rise up to exactly 25 feet. The rod breaks down the capability of reading to the 1/100th of a foot, 2 hundredths or 1/50th of a foot is approximately ¼ of an inch. This ensures an accurate measurement throughout the leveling process, keeping in mind most of the work we do does not necessarily require this tight of accuracy. Each One foot section is marked in BOLD Black numbers with alternating Red numbers to help keep track of the foot section you are reading. Further between the feet marks are the smaller numbers 1-9 or better known as the tenths. In-between those numbers are solid black ticks or “hash marks,” with white spaces between, each one of those represents the smallest measurement reading.
Differences between Grading Rods
As a rule of thumb surveyors carry benchmark elevations by using a leveling rod which usually extends to 25 feet. In addition the level rods are usually comprised of fiberglass, and have several sections that will allow the rod to extend higher for varying terrains. A Linker Rod only has a maximum distance of 10 feet vertically; this can cause a problem if trying to carry elevations along a route that has varying heights or drastic elevation changes. Also the size of the rod makes it more difficult to read at farter distances, however there is no requirement to calculate an instrument height, which saves time and is usually easier/faster to check or mass grade projects and reduces the human error of calculating a rod reading each time you take a side shot.
How Reading a Leveling Rod Works
When a surveyor or engineer calculates existing elevations or shoots elevation he needs a few components to calculate said grade. You need a known benchmark with type of datum, this benchmark might have been established by a FEMA, GPS, or previous surveys typically referencing sea level or maybe a city datum like Chicago typically runs between 0 and 100. When calculating your height of instrument or HI using a level rod, you take your existing benchmark (let us pretend the elevation of Benchmark Alpha is 100.00) and after you setup and level your instrument you read a 6.34. To obtain your Instrument Height you take the Benchmark and add it to your Rod Reading (100.00 + 6.34 = 106.34) which means your instrument is at 106.34, now ever shot thereafter is recorded as a side shot until you move or “turn” off another point. So if you were trying to obtain the elevation of another point and you read a 3.95 then the existing elevation is obtained by taking your HI (Instrument Height) and subtracting your SS (side shot) (106.34 - 3.95 = 102.39) As you can see this takes time to calculate and write down each reading just to obtain an existing elevation.
Linker Rod Procedure
The linker rod cuts this step out by storing your HI. Compare this to using an Linker rod it actually stores your HI by setting the rod to the benchmark elevation and all points read after that are the actual elevation in juxtapose to the said benchmark. Confused? Let me explain. If your benchmark elevation is 736.95, you would set the linker rod at 6.95 by telling your partner “up or down” till you read exactly 6.95. Once you get it to 6.95 he would lock the rod at the elevation, and then if you read 3.75 on the next Side Shot (SS) you would be recording a 733.75 as that locations elevation. Basically the rod does the work and thinking of what you and I would calculate when using a standard leveling rod.
Metric & English System
Most of us are understand inches and feet, the English system takes one foot and breaks it into 100 parts using what we refer in the field as 10ths and 100ths. One Inch basically breaks down to .0833333 feet or roughly 8 hundredths if you are looking to convert (3 inches = 0.25’). Metric however is more accurate because the distances are smaller thus on bridge and critical jobs where Millimeters are required they make Metric grading rods which provide a higher degree of accuracy and closure. Metric is typically used on tighter tolerance projects like bridges, where the degree of accuracy is critical.
Personal Usage and Experience
The 6 Section Fiberglass Level Rod has several uses besides the standard reading and running level loops.
Because of its fallibility and longer distance it can be used to obtain manhole invert elevations. Basically this practice is known as (Rim to Invert), where we obtained the manhole’s rim elevation then use the 6 Section Fiberglass Level Rod to “dip” or measure the distance to the pipes within the manhole also recording size and type information. This practice can be used on almost any type of manhole up to 25 feet deep, of course one must be careful in extremely deep manholes not to lose the rod itself.
Another expressed purpose of using the 6 Section Fiberglass Level Rod would be for situations where heights of surveying require more than the standard 8.5 foot prism rod. See the inventors of the level rod knew that it could be used in the field for more than just a tool of the trade, but rather several areas of surveying. Now with the capability to screw a glass prism on top of the 25 foot rod we are able to go over and above high trees and other obstructions to acquire elevations and information of those shots, not previously viewable without moving the instrument. This is both a money and time saver for the company and project budget.
Well the truth is you can use this rod for any measurement purpose vertically or horizontally as it reads true to a standard tape. There are no tricks to measuring just solutions in the field. We’ve used this particular rod for many years on all types of road, bridge, underground, and construction surveys with great success. I highly recommend that each survey vehicle is equipped with a 6 Section Fiberglass Level Rod not only for leveling purposed, but as a tool to complete work in a timely accurate fashion. I can easily recommend Cst/Berger brand Level Rod for any professional looking to get the job done.
Proper Survey Practice
Math is a wonderful discovery which seldom lies in the field of engineering and surveying, so remember to close out all of your bench loops by “kicking a leg” and tying back into existing benchmarks or other known elevations.
Always cover your butt by checking your entire notes with a calculator, and even having a team member double check the work helps prevent costly errors.
Don’t leave your traverses or loops open-ended, you must close the elevations of addition and subtraction to determine the error in your readings and if proration is necessary to correct human reading errors.
If you want to make your Crew Chief (The Boss) happy always put the rod back in the proper storage case to prevent nicks, scratches, and dirt damaging the reading surface.
Most E-Levels and Auto-Levels are setup on a Fiberglass or Aluminum Tripod.
Additional Survey Equipment Reviews
Chrisnik Survey Mag Nails
Understanding Survey Field Paint Markings
How to Read a 10' English System Surveyors Linker Rod
Thank you for Reading DeRango