Measure And Fix

2024 Author: David Durham | [email protected]. Last modified: 2023-12-16 02:26

Why do we need measurements

Measurements are the basis of the working documentation required for reconstruction, overhaul, interior design, and in some cases, new construction. The quality of the future project largely depends on the reliability of the source documentation.

Measurements are necessary if:

• lost project documentation;
• the function of the building, number of storeys, operational loads have changed;
• critical defects and damage to the building have occurred;
• construction is resumed after a long time;
• a new building is under construction next to the object;
• restoration or reconstruction is required.

Traditional fixing methods: pencil and tape measure

Architectural measurements are the main way to capture the characteristics of a building. They include:

• large-scale orthogonal drawings of the main projections of the building and its parts;
• the image of the building and its fragments in drawings;
• artistic and documentary photography.

An exhaustive idea of the object can be given, first of all, by measuring fixation. But dimensional drawings are extremely laborious, their execution requires time and a lot of various tools: rulers, ordinary and laser tape measures, steel strings, calipers, probes, templates, goniometers, levels, plumb lines, magnifying glasses, measuring microscopes.

The most common tool is the laser tape measure: cheap, compact and easy to use. It can be used to measure rooms and small buildings with simple geometry. But errors are inevitable: you have to direct the point from your hand, it is not always easy to maintain horizontal position, sometimes there is no line of sight between the points. The measurer must constantly adjust to the geometry of the room and choose the most suitable method - serifs, polar, by pillars, etc.

For more accurate and complex work, geodetic equipment is more suitable. This article will focus on the terrestrial laser scanning method and a specific model of the laser scanner - BLK360.

Laser scanning

Terrestrial laser scanning is the most complete and accurate measurement method available today. The laser rangefinder is built into the device, the direction of the beam changes automatically, the servo drive measures its vertical and horizontal angles.

A modern 3D laser scanner produces more than a million measurements per second and stores the received digital data in the form of an array of three-dimensional coordinates - a point cloud, which is actually a 3D model of the surveyed object. Each point, in addition to three geospatial coordinates, carries information about the color, which is recognized by the intensity of the returned signal. Thanks to the built-in cameras, it is possible to receive the entire data array in colors that correspond to real ones.

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  1/4 An example of a processed point cloud, a 3D model of a residential building in Switzerland. HEXAGON

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  2/4 An example of a processed point cloud, a 3D model of a historic quarter. HEXAGON

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  3/4 Example of processed HEXAGON point cloud

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  4/4 Example of processed point cloud, HEXAGON 3D model

The laser scanner, thus, draws the most complete "picture" of the object, from which it is easy to extract the desired parameters. This is the fastest way to obtain information that does not require any processing: you just need to import the data to your computer and then work with the "cloud".

If you need decorated materials, then the point cloud is exported to CAD systems, where accurate dimensional drawings, plans, sections, sections are created, or 3D models are built. Point clouds are supported by Autodesk, Graphisoft, NanoCad, common pts, las, e57 and others serve as exchange formats. There are a number of free viewers that allow you to take measurements: Autodesk Recap, Leica TrueView other.

Laser scanner Leica BLK360

The Swiss company Leica Geosystems has created the Leica BLK360 laser scanner, which combines the advantages of all measurement methods. It is lightweight and compact: weighs no more than a kilogram, fits in a bag or backpack, allowing you to scan anytime, anywhere.

Here are just a few of the advantages of the Leica BLK360:

• laser scans 360,000 points per second at a distance of up to 60 meters;
• the sensor works continuously for two hours on one battery charge;
• you can work indoors and outdoors, at a temperature of + 5-40 ° С;
• the errors are minimal: the sum of the angle and distance errors gives an error of 6 mm at a distance of 10 m and about 8 mm at a distance of 20 m;
• 15MP 3-camera system, HDR spherical panorama and LED flash;
• three modes of scanning density;
• The scanner is easy to work with: just watch the training videos with a total duration of about 25 minutes and follow the shooting methodology.

Just press one button - and in less than three minutes BLK360 will perform a panoramic scan of the surrounding area with capturing photographs. All information is transmitted to the iPad Pro tablet in the application for remote control and data control Autodesk Recap.

BLK360 in Action: Examples of Solved Problems

Initial measurement and work control

Let's see how BLK360 works on the example of a design project development. Object - a three-room apartment with a total area of 99 m²… The initial data is the BTI plan, it was digitized and transferred to the Autodesk AutoCAD environment. The corners of the room were freed up, and it took no more than five minutes to sweep and prepare the equipment.

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  1/4 BTI plan © HEXAGON

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  2/4 Drawing in AutoCAD © HEXAGON

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  3/4 Room preparation and equipment installation © HEXAGON

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  4/4 Room preparation and equipment installation © HEXAGON

In an hour, we completed 17 laser scanner installations. Panoramic images transferred to the tablet helped to control the accuracy of the location and the completeness of the data received. If necessary, it was possible to add measurements and comments right on the spherical panorama.

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  1/3 Example of commenting in the project © HEXAGON

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  2/3 Working draft in application and Recap © HEXAGON

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  3/3 Working draft in application and Recap © HEXAGON

We removed unnecessary elements from the point cloud - construction waste, furniture - and loaded it into Autodesk. Using a plugin CloudWorx in the AutoCAD environment, sections were built and walls were drawn in semi-automatic mode. The entire processing process took about 3.5 hours.

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  Point cloud in AutoCAD © HEXAGON

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  3D object view © HEXAGON

Let us compare the resulting contours of the walls with the drawing made according to the BTI plan: the green lines correspond to the actual position of the walls, and the white ones correspond to their planned position. As you can see, the difference in the position of the walls in some places is significant. It became possible compare floor areas: No discrepancies found here. The updated data was sent to the design bureau - you can safely continue working.

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  1/3 Examples of discrepancies between the planned (white) and actual (green) wall positions © HEXAGON

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  2/3 Examples of discrepancies between the planned (white) and actual (green) wall positions © HEXAGON

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  3/3 Examples of discrepancies between the planned (white) and actual (green) wall positions © HEXAGON

Primary scan is suitable for refinement of geometry premises, calculating the necessary dismantling volumes and design project development.

Scanning can be performed several times to fixing and monitoring the performance of work … The images show such works as moving the opening, installing the channel, sealing the opening with gas blocks and finishing.

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  1/6 Different stages of room scanning © HEXAGON

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  2/6 Different stages of room scanning © HEXAGON

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  3/6 Different stages of room scanning © HEXAGON

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  4/6 Different stages of room scanning © HEXAGON

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  5/6 Repairs © HEXAGON

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  6/6 Design project © HEXAGON

Coordination and control of the position of internal engineering networks

Another of the tasks to be solved is fixing the positions of internal engineering networks. In this example, these are electrical wiring and cable ducts for split air conditioning systems. The positions of the strobes were fixed, and potentially dangerous zones were plotted directly on the point cloud. Based on this data, it became possible at any time to get a binding for any element and to avoid hitting the network during further work.

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  1/4 Cloud of points of the groove point for air conditioning cables © HEXAGON

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  2/4 Cloud of points of the slot for the power cable © HEXAGON

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  3/4 Vectorization of potentially hazardous areas for other work © HEXAGON

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  4/4 Isometric view of internal power networks © HEXAGON

Finding surface deviations from the vertical

The data was additionally transferred to specialized desktop software for processing point clouds - 3DReshaper … Then they built perfectly vertical "theoretical" walls and compared the actual geometry of the wall with this ideal model. The result obtained made it possible to quickly find the defect, determine its area and, as a result, calculate the amount of material required.

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  1/3 Comparison of the actual wall geometry with the ideal model. © HEXAGON

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  2/3 Comparison of the actual wall geometry with the ideal model. © HEXAGON

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  3/3 Comparison of the actual wall geometry with the ideal model. © HEXAGON

The graph and scale of color identification to the right of the image are customizable, they help to understand how many dots are included in the deviation interval selected by the user. In this case, all points falling within the range of deviations from -5 to +5 mm from a perfectly vertical wall have a rich green color, and points whose values deviate by 2 mm were excluded from the comparison. It is always possible to get a scan of a wall or any required area.

Counting the volume of materials

Consider the solution to a common and rather monotonous problem - calculating the volume of plaster. According to the technical documentation, the consumption rate of the mixture corresponds to 8.5 kg / 1 m² with a layer thickness of 10 mm.

There are several traditional calculation methods, we will consider two of them:

• approximate: the thickness of the plaster layer is taken equal to 10-15 mm, additionally a margin of 10% of the reference indicator is taken into account, with rounding up.
• spot measurements: the average layer thickness is determined taking into account the angular deviations. For this, the surface on which the plaster will be applied is measured in three places. The values obtained when hanging are summed up and divided by the number of measurements by three.

The calculations are simple, but very rough. The second method requires preparation, sometimes in the form of plastering beacons. The professionalism of the plasterer is also a significant indicator.

We calculate in different ways how much material is required to level one wall with an area of 9.5 m².

• Approximate: weight of material without stock is 81 kg and 89 kg with 10% stock.
• Spot measurements: Spot measurements for dents and bulges gave values of 11, 8 and 10 mm. Average thickness ~ 10 mm. Material weight without stock is 81 kg and 89 kg with 10% stock. With this method, the results strongly depend on the random choice of the measurement site, even if the geometry of the marks is chosen correctly.
• Calculation of volume. Comparing the actual surface of the wall with the ideal one, we obtained a deviation map. It is noticeable that the figure has deviations from the design in both directions, therefore, the volume enclosed between the projected vertical wall and the actual position was calculated, it is 0.083 m³… We expect to display the wall by 10 mm, this will require 71 kg. In this case, you do not need to stockpile the material.

It should be noted that in all cases, three bags of plaster weighing 30 kg will be required. The resulting surplus can be used on other walls, but an initial accurate calculation will help to avoid excessive inventory and, as a result, save money. Especially considering that the total area of the walls is 280 m².

Checking the evenness of the screed

The evenness of the screed is checked using a two-meter rail-rights and la. The rail is applied to the screed in several places in different directions. According to existing building codes, the screed is considered even if the gap between the screed surface and rights and scrap does not exceed 4 mm.

It is also necessary to check the slope of the floor screed surface to the horizon. This value in any place of the screed should not be more than 0.2%, and in absolute value - 50 mm. So, for example, if the length of the room is 3 meters, then the deviation should not exceed 6 mm. If any defects are found, the customer has the right to call an expert. If the examination shows that the claims are justified, then the builders must pay all the costs of the expert's work and the elimination of the marriage.

Terrestrial laser scanning allows you to monitor large areas, spending a minimum of time. And the reliability and completeness of the data will completely eliminate the omission of problem areas. A similar control method was used during the construction of a shopping center in Lipetsk.

findings

To summarize, laser scanning has a number of significant advantages, namely:

• completeness of the received data excludes repeated visits for additional measurements;
• information is easy to perceive and interpret thanks to visualization and easy navigation in the software;
• combining scanned data with a photograph makes it easy to annotate and mark complex nodes;
• initial material may be sufficient for the development of design projects;
• the flexibility of working with data allows you to choose the most convenient technological scheme for the end user.