One of the more underestimated tools within a surveyor’s toolset is a leveling staff. It is usually used in conjunction with a transit or a leveling instrument, used to measure the height of a certain object. Then, you can use those findings to determine the elevation difference between the two points.
Staff leveling is an essential part of your surveying equipment, and as such should be considered with care. There are different types of staff levels and to help you determine which one should work for you, we aim to cover the topic of staff leveling in its entirety, telling you everything there is to know about it and allowing you to ultimately pick the one for your needs.
What is a Leveling Staff?
A leveling staff in surveying is also known as a survey rod or a leveling rod. It is a type of tool, mostly used in construction and land surveys, that helps to measure vertical heights. You will recognize it as it being a long straight rod with a graduated scale marked in both feet and meters.
A leveling staff is usually used with a type of leveling instrument, usually a dumpy level, an optical level, or even a laser level, which is needed to check the elevation of points on the ground. It is made out of durable materials, such as aluminum or fiberglass, but lightweight enough making it easier to move around.
A typical leveling staff length is between 10 and 16 feet, but can be extended or collapsed depending on your needs. The scale is marked in alternative white and black or red, which makes it easier for surveyors to read.
A surveyor would usually hold a leveling staff vertically along with a leveling instrument at the measuring point so as to set up a known location of sight to the top of the staff. The operator would then read the measurement on the staff at the level of the instrument’s line of sight. The acquired measurements will then be used to calculate the elevation difference between the two points.
Types of Levelling Staff in Surveying
The functionality of a leveling staff depends on its contrasting graduations allowing them to be easily read from a distance through a telescopic sight. To help make things easier for surveyors, there are different types of leveling staff in surveying that come into question.
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Survey Levelling Staff |
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2m Invar Barcode Precision Staff for Leica LS/DNA Digital Levels |
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Self-Reading Staff
A self-reading staff is the version that allows the observer to read the measurements directly through a telescope without having to include any intermediate steps. These types of staffs are pretty straightforward to use and are very efficient and actually eliminate the need for you to carry additional equipment or have additional staff with you. They are mostly used in leveling and surveying types of tasks mostly due to their simplicity and ease of use.
There are three different types:
- Solid staffs: Typically 3 meters in length constructed as a single continuous piece. They offer greater accuracy in reading measurements thanks to the absence of sockets or hinges.
- Folding or hinged staff: Usually made out of quality seasoned timber to ensure durability and precision. They come in 4 meters in length, composed of two 2-meter pieces connected by a hinge. The thickness is usually 18mm, while the width is 75mm.
- Telescopic or Sopwith-Type Staff: This one consists of three interlocking parts. The top section consists of a 1.25-meter solid piece, while the central and the lower section are 1.25m and 1.5m respectively. These pieces fit each other in a telescope manner and when fully extended measure up a total length of 4 meters.
Target Staff
The target staff is comprised of two sections, a 6-foot-long upper rod and a 7-foot lower one. The upper rod slides into the lower one, allowing for adjustability and compatibility when transporting it. There is also a movable target that comes with the rod, which you can move up or down during measuring.
The staff is usually graduated in feet and comes with subdivisions of tenths and hundredths, which accounts for very precise measurements. While reading, the staff level engineer would instruct the staff man to move the target up or down until it is perfectly bisected by the level’s line of sight.
Once the target is perfectly aligned, it is clamped in place so readings can be recorded. This process will ensure accurate measurements are taken while the target will help create clear and precise readings.
Factors to Consider when Choosing a Leveling Staff
Picking a staff for leveling is not as easy as you think. There are a variety of factors that come into play and if you are not sure what you need it for, you may end up picking the wrong one. So there are several characteristics that you need to consider that will allow you to pick the one that you ultimately require.
Materials and Durability
A leveling staff for surveying is usually built out of materials such as wood, aluminum, or fiberglass, with each one having its own characteristics. Wood is the most traditional type of material which offers stability and accuracy, but is susceptible to moisture and temperature changes.
Aluminum is lightweight and durable, but also prone to corrosion. Fiberglass is also very lightweight and is a non-conductive type of material. Its resistance to corrosion actually makes it the best type of material for leveling staff.
The main thing that you have to consider when picking a suitable staff is the conditions you are going to be working in. If you happen to be working in humid conditions, aluminum or fiberglass staffs are more suitable. Additionally, consider the wear and tear of leveling staffs that they might go through, so going for durable materials is worth the investment.
Length and Extendibility
Leveling staff height usually ranges from 10 to 16 feet. The length of the staff depends on the project you plan to work on and the positioning of the objects you plan to measure. 12-foot long staffs are usually more than enough for commercial or residential objects. But if you happen to be working on much bigger projects, you might need to consider getting a longer staff right off the bat.
Also, consider expandable staffs instead of those that cannot be collapsed. Movability and transportation is made much easier if you can collapse the staff while moving it about.
Graduation and Accuracy
The graduation on a leveling staff refers to the markings that indicate its height. You need to get a staff with clear and accurate graduation as you don’t want it affecting the precision of your measurements.
The graduation usually comes in feet or meters, but also includes smaller subdivisions allowing much more precise measurements. It is best to look for a staff with high levels of accuracy, preferably within 1/16 inch or 1mm.
Weight and Portability
If you plan to transport your level staff frequently, then you should be taking its weight into account. Picking a lightweight staff will allow you to transport it much easier and also will help you move it along the surveying site with ease. But be sure to balance the weight and durability. A very light staff may be less sturdy and could be easily damaged.
Portability is also an important factor. Since there are a variety of staffs that can be folded or collapsed, you might want to pick those if you are going to do a lot of fieldwork. If your work includes a lot of movement in the field, also consider one with a carrying case or a strap.
Cost and Budget
Leveling staff price ranges from budget-friendly options to expensive high-end models. The cost of the staffs depends on the material, accuracy, its length, and, of course, the brand. Going for the cheapest option is definitely not a good idea, especially plan to use it long-term.
Investing in good staff is certainly the best way to go, as it will last longer and produce better results. But if you don’t plan to use it that much, a middle-priced option would work the best.
What is Leveling?
When it comes to leveling in surveying, it is mainly used to determine the relative height of different points situated on, above, or below ground surface. This process involves calculating the elevation differences between two locations on the earth's surface. Measurements are taken from a reference point that has established parameters, such as elevation or height above mean sea level (MSL).
The objectives of leveling in surveying are twofold: first, to calculate the elevation of specific points in relation to a provided or assumed datum or reference line; and second, to establish points at a designated elevation or across various elevations based on that same datum.
Methods of Levelling in Surveying
There are several methods of leveling used in surveying that can help to determine the elevation of various points.
- Direct Leveling: The most common type of leveling in surveying is spirit leveling, where a spirit level attached to a telescope ensures a horizontal line of sight. Vertical distances are then measured from this line to determine the elevation differences between various points.
- Trigonometric Leveling: An indirect leveling method used to determine elevation differences by calculating horizontal distances and vertical angles. This technique is often employed when direct leveling is impractical, such as when measuring the height of mountain peaks or tall structures.
- Barometric Leveling: Another indirect leveling technique for determining elevations based on changes in atmospheric pressure, which decreases as elevation increases. This method typically uses an aneroid barometer to measure these pressure changes.
- Hypsometric Leveling: An indirect leveling method that calculates elevation based on changes in the boiling point of water, which decreases as altitude increases.
Types of Levelling in Surveying
There are several types of direct leveling that surveyors tend to use.
- Simple Levelling: This is the most straightforward type of direct leveling, requiring only one instrument setup. It is used to determine the elevation difference between two points that are visible from a single instrument position.
- Differential Levelling: This method involves multiple instrument setups and is used when the two points whose elevation difference needs to be measured are located far apart.
- Check Levelling: A form of differential leveling, check leveling is performed to verify previously obtained elevations. Typically conducted at the end of each workday, it involves measuring from the last station back to the starting point or connecting to a known benchmark (B.M.) instead.
- Fly Levelling: This type of differential leveling is used to quickly estimate approximate elevations at various points. Fly leveling prioritizes speed over precision and is often employed for area reconnaissance or rough-level checks.
- Profile Levelling: Also referred to as longitudinal leveling, this method determines ground surface elevations along a designated line. The data collected during profile leveling is essential for plotting longitudinal sections, used for tasks like establishing gradients and calculating earthwork quantities.
- Cross-section Levelling: This method, another form of differential leveling, measures elevation differences along a line perpendicular to the centerline of a proposed road.
- Reciprocal Levelling: Used when two distant points cannot be directly measured due to obstacles (like rivers or valleys), reciprocal leveling involves setting up the instrument on one side and taking measurements from the other, then switching positions.
- Precise Levelling: This highly accurate form of differential leveling is utilized for critical projects where precision is essential.
Application of Levelling in Surveying
You are going to find a variety of uses of leveling necessary during surveys. The most common types include.
- Project Estimation and Design: Levelling is essential for the estimation and design of various civil engineering projects, including roads, bridges, and canals.
- Route and Alignment Surveying: It is necessary for surveying the routes and alignments of highways and bridges.
- Earthwork Activities: Levelling is crucial for earthwork processes, such as cutting and filling.
- Pipeline Surveys: The technique is used in pipeline surveys to determine optimal routes and slopes for smooth flow within the pipelines.
- Map Preparation: Levelling also assists in the creation of contour maps and topographic maps.
FAQs
For the end, we provide you with a few commonly asked questions.
How to read a leveling staff in surveying?
To read a leveling staff in surveying, first one needs to set up and level the instrument. Hold the staff vertically over the point of interest, ensuring it remains straight. Direct the telescope towards the staff and focus it until the horizontal cross-hair aligns with a graduation on the staff. Take note of where this cross-hair intersects, which indicates the elevation reading in meters, decimeters, and millimeters. Finally, record the reading accurately, keeping in mind that the staff appears inverted through the telescope.
What is leveling staff in surveying?
A leveling staff is an essential surveying tool, typically made of wood or composite materials and graduated in metric or imperial units. It is held vertically at the measurement point, with its base as the zero reading. When viewed through a leveling instrument, the staff's graduations indicate the height of the instrument's line of sight above the ground.
What is leveling in surveying?
Leveling in surveying is a branch which determines the elevations of specific points relative to a given or assumed datum. Its primary objectives are to find the height differences between various locations and to establish points at designated elevations, which is essential for designing and setting out engineering projects like roads, bridges, and canals.
How to read a leveling staff?
To read a leveling staff in surveying, first level the staff properly. Hold the staff vertically over the measurement point, then look through the telescope and focus on the staff until the horizontal cross-hair aligns with graduation. Take note of where the cross-hair intersects the staff, which indicates the elevation reading in meters, decimeters, and millimeters.
