N
ivelir at a construction site, the second most important tool after a measuring tape. Having no idea how to work as a leveler, there is no point in even thinking about starting any more or less serious construction. At the same time, the operating principle of the level and the basic techniques for working with it are so simple that even a primary school student can master them.
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Video version of the article
Level device
Let's look at what a regular optical level consists of and how it works. The main part of the device is an optical tube with a lens system capable of zooming in on observed objects with a magnification of twenty times or more.
The pipe is mounted on a special rotating frame, necessary for the following functions:
- tripod mounts;
- setting the optical axis of the level to a strictly horizontal position, for which the frame has three height-adjustable “legs” and one or two (in models without automatic adjustment) bubble levels;
- precise horizontal aiming, which is carried out with paired or single handwheels.
In some models, the bed has a special dial, a scale that allows you to measure or construct horizontal angles.
On the right side of the pipe there is a handwheel designed to adjust image sharpness.
Adjustment to the operator's vision is made by rotating the adjustment ring on the eyepiece.
When looking through the eyepiece of a level telescope, we will see that in addition to bringing the object observed through the device closer, the level superimposes a system of thin lines on its image, called a reticle or reticle. It forms a cross-shaped pattern of vertical and horizontal lines (see Figure 1).
Additional devices and equipment
In addition to the device itself, for work we will need the already mentioned tripod, as well as a special measuring rod with divisions and numbers printed on it. The divisions are stripes of alternating black or red stripes 10 mm wide.
The numbers on the rod are marked in increments of ten cm, and the value from zero to the end of the rod is in decimeters, with the numbers expressed in two digits. So, 50 cm is designated as 05, the number 09 indicates 90 cm, the number 12 indicates 120 cm, etc.
For convenience, the five centimeter marks of each decimeter are also united by a vertical strip, so that the entire strip is marked with signs in the form of the letter “E”, straight and mirrored.
For any type of construction, setting marks according to design data is mandatory. For this purpose, a geodetic instrument such as a level is used. There are two types of this tool: optical and laser.
The optical level is a horizontal circle, adjusted with special lifting screws and a telescope fixed in the upper part of the device. Before starting to work with it, the surveyor secures it on a tripod, centers it over a reference point and brings it to an absolutely horizontal position.
The device is ready for use when the bubble of the round level is in the center and does not move when the device is turned in different directions.
When performing a survey, you can rely on the Baltic coordinate system if there is a reference point nearby (a point with a known elevation above sea level), otherwise, a relative system is set and any one is taken as a reference point.
To determine the horizon of the instrument, a geodetic rod is installed on the reference point, on which a scale is printed graphically and in the form of numbers. The surveyor takes a mark from the crosshairs of the grids in the telescope and adds it to the mark of the reference point. This is where the horizon of the device is located.
To determine the elevations of other desired and unknown points, a geodetic rod is installed sequentially on each of them. The readings obtained are subtracted from the horizon of the instrument, the results obtained are the marks of the required points.
In order to avoid unnecessary work, a height gauge is installed in place of each point. The actual height obtained is either recorded on it, or the crossbar is installed at a height equal to the design one.
Based on these elevation marks, it is possible to carry out further work, be it filling the site with inert material to the design elevations or pouring the formwork with a concrete mixture.
It is not allowed to remove the level from its working position until all necessary geodetic work is completed. Otherwise, installation and reinstallation of the device into the working position is repeated according to the above algorithm and will take some additional time.
There are situations when one of the required points is inaccessible for visual reading on the staff. In this case, it is necessary to make a transition and reinstall the device to another location, thereby changing the horizon of the device.
The operating principle of a laser level is almost identical to an optical instrument. The only difference is that the laser beam is focused on the geodetic staff and there is no need to look at the reading through the eyepiece.
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The optical level is considered by many to be archaic, while it is one of the most accurate instruments in geodetic research. In our review, we will satisfy the interest of ordinary people regarding the use of a level for the geometric method of constructing planes.
Two surveyors on different edges of the abyss:
Leveler (shouting): Move over!
Reika: Whaaat?
Leveler (even louder): Move over!!!
Reika: I can’t hear!!!
Leveler (mumbling): Deaf idiot...
Reika (shouting): You're an idiot!!!
The essence and specifics of leveling
There are many ways to determine the curvature of the earth's surface: by the slightest difference in atmospheric pressure, using a theodolite or water level and other devices. However, geometric leveling is considered the most universal, fast and accurate method: even with technical levels used in construction, the measurement error is only 10 mm per km.
The essence of leveling is to determine the difference in height (excess) of each of a set of points on the ground relative to a certain reference point, called a benchmark in construction. After the virtual plane has been determined, a zero mark is measured relative to it, which in most cases lies at the floor level of the first floor of the building.
In principle, there is nothing complicated in leveling except for two specific points. On the one hand, the surveyor and his partner must be able to use a level and a staff, know the finer points of adjustment and correctly install control posts. Another nuance is that there may be objects on the ground that prevent visual contact between the level and the staff. Therefore, the installation site of the level has to be periodically moved, determining temporary reference points and establishing the height difference for them. But in the end, all calculations come down to banal arithmetic.
Determination of benchmark and key points
During a geodetic study of a construction site, the benchmark is placed at the lowest point of the plane, which is determined visually or by a cursory “shoot”. At this point, a massive pole with a straight cut is driven into the ground, on which it is convenient to install a rail.
The number and location of key points depends on the leveling tasks. If we are talking about preparing a foundation pit, the points are placed on the internal and external corners along the contour of the future structure. When placing control points, high precision is not required; it is only important that there are no local bumps or holes in the place where the stakes are installed.
Within the boundaries of a populated area there are special, measured and officially approved reference points for reference to them when measuring new construction sites.
All points should be as equidistant as possible from the level installation site and be at least 5 meters away from it. If you are leveling a small area, you can use a level to shoot all the points from the side, or use a hydrostatic level.
Installation and alignment of the visor
First you need to set up a tripod. Having loosened the screws securing the telescopic legs, the tripod needs to be aligned so that the upper platform lies in a horizontal plane; here everything is done “by eye”. The legs need to be pressed into the loose soil, pressing the foot against the stop, and the distance between them should be the same. The height of the legs must be adjusted so that the tripod platform is at chest level, and then tighten the screws.
When the tripod is installed, the level itself is attached to it using a central screw. It has two platforms: the lower one is fixed to the tripod with a screw or other standard method, the upper one rests on three adjusting screws. On the sides of the triangle formed by the screws there are three cylindrical pre-setting bubble levels. By rotating one pair of screws, you first need to ensure that the bubble between them is exactly between the marks. After this, by tightening the third screw, two other levels are set. The fine adjustment indicator - a round level - is located on the body of the level's optical tube. It may be necessary to turn the adjustment screws a little to ensure that the bubble is positioned exactly within the circle mark. The level is ready for use.
Leveling rod designations
Before you start shooting terrain, it's a good idea to figure out how to navigate the staff. Really, what are these incomprehensible letters “E”, what are these black and red marks? It's actually very simple.
The rail is divided into segments, each 10 cm long. Inside each segment there are black and white sections, each 1 cm long. The outer three black sections are united by a side line - this is to make it easier to visually determine the center of the segment. The numbers indicate in which ten centimeters the segment marks are located, that is, essentially the position on the rail is determined by the number of white and black sections added to the ten number.
But accuracy of one centimeter is clearly not enough. The fact is that on the back side of the staff there is a regular millimeter graduation, which is not very convenient to use over long distances. Therefore, the assistant holding the staff can further adjust the slider, guided by the surveyor’s commands “above” and “below”, and then show the number of millimeters on his fingers. Also, some levels are equipped with a metric grid, which makes it even easier to determine this deviation.
Finally, the most interesting question: why the top of the rail has red markings located in the reverse order. The fact is that the old levels did not have an additional lens and the surveyor saw the image upside down. But you are unlikely to have to deal with such “dinosaurs”.
Procedure for measuring point elevation
Before shooting a point, an assistant should set the staff as close as possible to the control peg, gently resting it on the adjacent ground. During measurements, the rod must be held motionless and strictly vertical, using a plumb line or a round bubble level for alignment.
The level must be turned towards the staff so that the vertical axis of the grid is located exactly in its center. After this, by rotating the optical screw, you need to adjust the sharpness of the image so that the marks on the staff are clearly visible. Then you need to adjust the sharpness of the reticle display by rotating the ring on the eyepiece.
To determine the excess, you need to note the number of the segment on which the vertical axis is located, and then count how many whole black and white spaces there are from the beginning of the segment to the axis. By adding this value after the segment number, you will get the elevation in centimeters. If higher accuracy is needed, a comma is placed after the elevation, then the assistant moves the slider so that its edge exactly coincides with the horizontal axis and transmits the number of additional millimeters, which is written after the decimal point.
You can do without the slider. If the horizontal axis is located exactly in the middle of the white or black mark, add three millimeters, if in the lower quarter - one or two, if in the upper quarter - four. This visual definition is more than enough for construction.
Logging and calculations
The leveling process involves keeping a large number of records. The surveyor should have at hand a site plan, which schematically shows the object for the construction of which leveling is being carried out, as well as the location of the control stakes. Each peg must be numbered and these designations must be placed in a separate table in which the measured excesses are noted.
Now about the excesses themselves. They can be relative and absolute, that is, from the level measurement plane and from the benchmark. For example, the excess of the reference point was 145.2 cm, and the reference point - 151 cm. Subtracting the excess of the point from the excess of the reference point, we find that the absolute excess will be -4.8 cm, while the minus sign makes it clear that the current is located below. Similar calculations should be carried out for each of the points.
The practical meaning of leveling is to apply marks on the stakes that are in the same horizontal plane. To do this, you need to find the highest point with the largest positive value of the elevation and add to it, for example, 20 cm. Following from one peg to another, using a tape measure, mark the value of the elevation of the point on them, to which the offset value is added - those same 20 cm. The resulting marks are used when excavating and determining the depth of the pit, or for pulling the mooring cord.
Many novice builders want to know how to use a level. To learn how to work with this device, you just need to learn the basics and test the device. After this, even beginners in construction will be able to perform accurate measurements as well as specialists.
Leveling the terrain is necessary to determine a level surface.
Elements needed for leveling:
- ordinary level;
- tripod;
- planks;
- ruler.
How to level correctly on the ground?
Levels are a group of devices that can be used to check the evenness of a surface or determine the exact height position of certain objects. Objects can also be random marks or areas of the earth's foundation; it is not necessary to use specific landmarks.
The purpose of any leveling method is to determine the difference in heights between the elevations of the building being erected.
The quality of construction work will depend on the magnitude of such excess and its correct measurement. From the estimated zero level of the lower floor of the building, you can determine the depth of the foundation, groundwater flow, etc.
Options for leveling on the ground:
- Hydrostatic measurements. Based on the property of equal placement of liquid in combined vessels. They have 100% accuracy and allow you to take measurements beyond the line of sight between selected marks. This method of measurement involves laying and filling long tubes with a special liquid, which is not always convenient to do. Therefore, this method is used extremely rarely.
- Trigonometric method, which uses a rotary theodolite. The advantage of this method is that you can take measurements yourself. Similar measurements can be taken in corners, but understanding this device is much more difficult than with an ordinary or laser level. It should also be taken into account that it is very expensive.
- Barometric measurements are used in the process of drawing up plans and marking large-sized architectural complexes. In this case, to take measurements you will need to purchase barometers and install the program on your computer. Measurements using this method are practically not carried out in private residential construction, since the elements necessary to complete the work are not cheap.
- The geometric method allows you to measure elevation angles using simple levels. It is correct to take measurements in a single plane. In this case, specialists set marks, move them from one place to another and make entries in the measurement log.
The simplicity of measurements using a simple level, its compatibility with the needs of building houses, made this device the most popular when designing various types of work - from pouring the base to determining the accuracy of a gable roof.
To work with an ordinary level, you definitely need a partner who will hold the ruler. The exception is the use of the trigonometric method.
Level design
The level has a simple design. An optical unit with a built-in lens system is placed on a durable tripod.
There are graduations on the sides of the bar. On the outside, the markings are made in the metric measurement system, and on the back - in the inch system. The bar should be installed with a special mark on the bottom bracket in the center of the measurement point. To make it more convenient to hold the device at this point, you need to use special handles.
Devices for determining the level are built into the tool body. A qualified specialist periodically checks the values shown by the sensors. If necessary, the tilt of the optical assembly can be adjusted using the handles. This makes it possible to identify deviations of the device from its exact placement on the territory. As a result, there will be no need to take measurements again.
The simplest and most economical are levels with a cylindrical level.
Budget models provide only one level, but there may be several. More expensive are designs with automatic compensation for installation errors. It is convenient to work with devices of this type on problematic soils. Structures with electronic measuring devices will be needed exclusively in the process of professional design of large buildings. They are difficult to set up and use.
Groups of modern devices
According to the measurement accuracy class, all levels are conditionally divided into three main groups:
- Technical devices. They are marked N-10, N-12, etc.
- Precision devices. They are marked from N-3 to N-9.
- Particularly precise devices. They are marked from N-05 to N-2.5.
The numbers in the markings indicate measurement errors in mm/km. Consequently, even technical equipment will give a deviation of approximately 1 cm per 1 km of distance to the object. This will be sufficient to properly plan most construction jobs.
A more modern design is the laser level. Instead of an air bubble, there will be a float in the water with a laser pointer. The float, which is immersed in water, is always located in a horizontal position in relation to the soil. Therefore, during use, you will need to vertically install the laser device, turn it on, secure the working position of the luminous mark, and then proceed from this guideline. The tool can be rotated in any direction. Height differences are measured with an ordinary ruler. It takes less time to install a laser level, so all measurements can be made faster.
If you try, you can use a laser level to take measurements yourself, without involving an assistant. This is a big advantage of this device. The disadvantage of the design is that it depends on power sources, batteries or solar panels. If you shake the device, the calibration may be lost. In this case, the laser pointer will move relative to the float. Please be aware that this may lead to inaccuracies.
Sequence of measurements using a standard level
First, the tripod is installed. The bolts for fastening to the legs need to be loosened, since the device often has to be mounted on rough terrain. After this, you should extend the stops to the desired length and tighten the screws to secure them on all supports. A considerable part of the tools are equipped with mounts for adjusting each tripod leg. With their help, you can fine-tune the horizontal position of the upper base.
The level is installed on the surface. By turning the bolts you will need to obtain the exact, central position of the level in relation to the marks. To make it more convenient to work, the first thing you need to do is place the bubble in one window, without taking into account the others. After this, the next level is adjusted, and it is important to monitor the position of the first. During the installation process, the first level may change its location. All actions must be performed slowly. As a result, it will be necessary to achieve horizontality at the installation site.
The next step is to focus the optical assembly. Before using this device, you will need to configure the level, set the location of the eyepiece of the aligned telescope according to the user’s vision. Each person has their own value for eye acuity. This applies even to those people who do not wear glasses. The focusing of an ordinary measuring device is done in this way: the device must be aimed at a large element, after which it is necessary to change the settings until the network is displayed on the object with 100% clarity. Further, similar actions should be repeated on the planks, which are mounted in other places. This type of focus adjustment on subjects that are lit differently will help make accurate measurements in the future.
Observations can then be measured and recorded. Once the fixture is mounted and focused, all engineering measurements can begin. Several strips must be installed in front and behind the device being used. The front will show the user the value of the height that is being measured. First of all, the tool must be pointed at the black side of the far bar. After focusing is completed, the obtained data on the far stroke should be recorded. After this, you need to focus on the front (main) bar.
At the next stage, you will need to fix the average.
Many experienced specialists were able to test the ordinary level at both small and large construction sites. It is safe to say that it is reliable and accurate. People have been using this device for decades, and during this time it has never failed. Therefore, there is no point in purchasing expensive models if you need to take measurements in private construction. Using a level is not a complicated process, you just need to know the correct sequence of actions.
Leveling is the measurement of the difference in height between certain points on a site. This definition is not from a textbook, but it seems clearer to us. Therefore, leveling means measuring the difference between two or more points in height. In this case, the device itself may or may not be tied in height to one of the nearby reference points. In most cases, when it comes to planting a house on a site, determining the height of its base, incl. taking into account the difference in heights with neighboring areas, for the purpose of planning the landscape of the area, draining rain and melt water from the house, etc., then such a connection is not necessary.
When we talk about a device, we mean a level - a geodetic altimeter. A reference point is a stationary sign that has a stable position in relation to the ideal reference point taken as “0”. They come in 3 types of significance (secular, fundamental, ordinary), but this is not the subject of this article. In real conditions, when building an individual house, any, usually the highest point of the site, is taken as a reference point, and all elevation differences are calculated from it.
Of course, you don’t have to level the area, but if you plan to at least excavate or backfill soil when organizing the landscape, then such a study will help you calculate its amount with high accuracy, which will minimize the cost of special equipment and transport. And you can’t really go wrong with the height of the plinth, and this is one of the most common mistakes made by individual developers, which is costly in the future.
Types of levels
Today, directly answering the question of what a level is is not as easy as it was a dozen years ago. At that time, this name meant an optical device that resembled a small telescope mounted on a tripod, through which marks on a staff located at a great distance from the device were clearly visible. According to the instructions of the operator, the assistant installed it at various points on the site. The image in it was upside down, which was a certain inconvenience for taking measurements. But the device was exceptionally reliable, which allowed it to survive to this day.
But at the same time, more convenient-to-use levels have entered the market, and in such a variety that it is easier to understand their variety using a comparative table.
From it we will isolate 2 main groups. And this:
- optical;
- laser
Optical levels have been replenished with a wide range of direct action levels, where the image is not turned upside down, as well as digital levels, in which the human function of keeping a leveling log and making calculations of level excesses began to be performed by the device itself. A person only has to press a button when pointing at the ruler and at the very end read the finished log from the level’s memory.
But, nevertheless, all optical levels require the operator to have at least a little knowledge about working with them.
Laser levels are so easy to use that no special skills are needed to use them, the main thing is that the device is clearly calibrated and configured.
The laser beam of such a level draws a clear luminous line in various planes, which radically simplifies all constructions and calculations. And in tandem with a regular tape measure, such a device allows you to easily perform all the tasks of a traditional level and even more.
The only noticeable drawback of laser levels is their limited use on a clear sunny day, but the most powerful models minimize this factor, and our Kulibins have found an elegant and simple way out of this situation.
Such levels are positional and rotary. The second differs from the first in the presence of a servomotor mounted on a suspension, which rotates the laser beam refracted in a prism at an angle of 900 around its axis.
The accuracy of such a device is higher.
Actually, all laser levels are such only in connection with a measuring rod, and without it they are laser levels, but in practice, the latter are considered to be low-power devices used indoors.
Most modern levels are self-leveling (naturally, within certain limits of deviations from the horizontal), but level models have also been preserved, where installation is carried out by levels, but we will deal with this below.
The difference in accuracy classes is not of great importance for our types of leveling, so we will deliberately omit their description.
How to use an optical level
The level is not a cheap device. Buying it for one-time measurements is hardly justified, and hiring surveyors for this work is even more wasteful. But, having become familiar with the basic techniques of working with a level, and renting it (and this is now possible everywhere), you will definitely be able to carry out all the work with it on your site yourself.
The design of most optical levels is similar, and differs mainly in the presence or absence of a rotary dial, which makes it possible to determine angles on a horizontal plane with an accuracy of 50, and the design features of individual elements.
You saw the principle of working with an optical level in the video presented above. Now let's look at how to work with it.
The work is carried out by 2 people: one directly with the device, installing, pointing the ruler at the target, reading and recording the indicators, and the second with the ruler, carrying and installing it according to the instructions of the first, making sure that it is vertical.
The level is installed on a tripod.
The main function of a tripod is to accurately hold the device in the established position, preventing deviations from the set level, and also protect it from tipping over. Retractable legs allow you to fix the level at a given height with horizontal positioning of the mounting area, even on sloping terrain. Tripods are often equipped with a level on a suspension, and modern ones can be equipped with other systems for balancing the device.
Most of the leveling slats (rulers) have the same designations in the form of divisions with a thickness (value) of 10 mm, some of which, for ease of reading indicators, are combined into a straight or reverse letter E, having a height of 50 mm. There is also a distance of 50 mm between these letters. Large numbers on the staff indicate distances in decimeters.
Depending on whether your level is direct or reverse, the reading is made either from above or from below. The application of values on the staff must also be direct or reverse. Some of the slats for direct levels are equipped with a scale that is more familiar to us. They also have a telescopic device for easy transportation.
You can select the level installation point on the ground.
But the main thing: its clear level setting. Bubbles on all built-in levels must be strictly centered.
It is better to immediately prepare a plan of the site with marks in which you will position the staff and on such a plan record the real indicators of the level.
This is what professional surveyors or builders do. There are other forms of keeping a leveling journal, but you can record your results in any form convenient for you, which most accurately meets the tasks that you must solve during the leveling process: either plan the terrain, or set foundation height marks.
Making a level with your own hands
The level, in fact, despite its rather complex design, is one of the most easily made devices at home. It is based on the construction of an absolutely horizontal platform at a given point.
The principle of the homemade level is clear from the diagram. We just have to comment on it and make the necessary, in our opinion, adjustments.
Firstly, It is not at all necessary that the support (platform) rotates. It is important that it is installed strictly horizontally and firmly so that it does not deviate from the initial position during the measurement process. To do this, it will be useful to install two braces in perpendicular planes, with which the platform can be rigidly secured to the leg.
Secondly, the leg does not have to be made in the form of a tripod - it is important that it rests confidently in the ground. To do this, you can simply drive it into the ground through a wooden spacer so that it does not wobble, and secure the platform using a well-calibrated level.
Third, the role of the level itself will fulfill this level. You can take measurements by aiming at the rod along its edge (in this case, the person holding the rod must follow your commands by moving a contrasting object such as a credit card along the scale), or you can attach a powerful laser pointer to the level.
Moreover, even if the laser point is blurry, you can easily calculate the center of this light spot by taking the dimensions along one of its edges - after all, when leveling, what is important to us when leveling is the difference in heights, and not its exact deviation from sea level.
And the slats can be made from any flat wooden slats or some kind of pipe, attaching a tape from a broken tape measure or even a tailor's tape measure to them.
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