What is a CT scan. How does it work. What are the different types of CT scans. When is a CT scan necessary. How to prepare for a CT scan. What are the risks and benefits of CT scans. How is a CT scan different from other imaging techniques.

Understanding CT Scans: Basics and Technology

Computed Tomography (CT) scans are advanced diagnostic imaging procedures that combine X-ray technology with computer processing to create detailed cross-sectional images of the body. These scans provide a more comprehensive view of internal structures compared to traditional X-rays, allowing healthcare professionals to diagnose and monitor various medical conditions with greater accuracy.

How CT Scans Work

CT scanners use a rotating X-ray beam that circles the body, capturing multiple images from different angles. These images are then processed by a computer to create detailed two-dimensional or three-dimensional representations of the body’s internal structures. This technology allows for a more in-depth examination of bones, muscles, organs, and blood vessels.

• X-ray beam rotates around the body
• Multiple images are captured from various angles
• Computer processing creates detailed cross-sectional images
• 2D and 3D representations are possible

Why are CT scans more detailed than standard X-rays? Unlike conventional X-rays that produce a single image, CT scans capture multiple views of the same area, providing a more comprehensive and detailed picture of internal structures. This allows for better visualization of soft tissues, organs, and subtle abnormalities that might be missed on a standard X-ray.

Types of CT Scans and Their Applications

CT scans can be performed on various parts of the body, each with specific applications and benefits. Understanding the different types of CT scans can help patients and healthcare providers make informed decisions about their diagnostic needs.

Common Types of CT Scans

1. Head CT: Used to examine brain injuries, tumors, or bleeding
2. Chest CT: Evaluates lung conditions, heart issues, or chest injuries
3. Abdominal CT: Assesses organs in the abdomen, such as the liver, kidneys, and pancreas
4. Pelvic CT: Examines reproductive organs and pelvic bones
5. Spine CT: Investigates spinal injuries, herniated discs, or degenerative conditions
6. CT Angiography (CTA): Visualizes blood vessels and detects blockages or aneurysms
7. Virtual Colonoscopy: Screens for colon cancer and polyps

When is a CT scan necessary? CT scans are often recommended when a more detailed view of internal structures is required for accurate diagnosis or treatment planning. They are particularly useful in emergency situations, cancer staging, and evaluating complex fractures or internal injuries.

CT Scans with Contrast: Enhancing Diagnostic Accuracy

Contrast media are sometimes used in CT scans to improve the visibility of certain structures or abnormalities. These substances can be administered orally, intravenously, or both, depending on the area being examined and the specific diagnostic goals.

Types of Contrast Media

• Oral contrast: Typically used for abdominal and pelvic scans
• Intravenous (IV) contrast: Enhances visualization of blood vessels and organs
• Double-contrast studies: Combine oral and IV contrast for comprehensive imaging

How does contrast media improve CT scan results? Contrast agents enhance the visibility of specific tissues, organs, or blood vessels by altering how they appear on the CT images. This can help radiologists detect subtle abnormalities, assess blood flow, and differentiate between normal and pathological structures more accurately.

Preparing for a CT Scan: Essential Guidelines

Proper preparation is crucial for obtaining high-quality CT scan results and ensuring patient safety. The specific instructions may vary depending on the type of CT scan and whether contrast media will be used.

General Preparation Guidelines

• Inform your doctor about any allergies, medications, or medical conditions
• Remove metal objects, such as jewelry or piercings
• Wear comfortable, loose-fitting clothing
• Follow fasting instructions if contrast media will be used
• Discuss any concerns or questions with your healthcare provider

How should diabetic patients prepare for a CT scan? Diabetic patients should consult their healthcare provider for specific instructions, as fasting requirements may need to be adjusted. Generally, they may be advised to eat a light meal three hours before the scan and to monitor their blood sugar levels closely.

Risks and Benefits of CT Scans: Weighing the Options

While CT scans provide valuable diagnostic information, it’s important to consider both the benefits and potential risks associated with this imaging technique.

Benefits of CT Scans

• Non-invasive and painless procedure
• Provides detailed images of internal structures
• Helps in early detection and diagnosis of various conditions
• Guides treatment planning and monitoring
• Can eliminate the need for exploratory surgery

Potential Risks and Considerations

• Exposure to ionizing radiation
• Possible allergic reactions to contrast media
• Increased risk for individuals with kidney problems
• Pregnancy considerations due to potential fetal radiation exposure

Are CT scans safe for everyone? While CT scans are generally considered safe, the risks and benefits should be carefully evaluated for each individual patient. Healthcare providers weigh the diagnostic value against potential risks, particularly for pregnant women, children, and individuals who require frequent imaging.

CT Scans vs. Other Imaging Techniques: Comparing Diagnostic Tools

Understanding how CT scans compare to other imaging techniques can help patients and healthcare providers choose the most appropriate diagnostic tool for specific medical situations.

CT Scans vs. MRI

• CT scans use X-rays, while MRI uses magnetic fields and radio waves
• CT scans are faster and better for imaging bones and acute injuries
• MRI provides superior soft tissue contrast and doesn’t use ionizing radiation
• CT scans are more widely available and less expensive than MRI

CT Scans vs. Ultrasound

• CT scans offer more detailed images of internal structures
• Ultrasound is radiation-free and provides real-time imaging
• CT scans can image larger areas of the body more effectively
• Ultrasound is often preferred for examining soft tissues and during pregnancy

When should a CT scan be chosen over other imaging techniques? CT scans are often preferred in emergency situations, for evaluating complex fractures, detecting internal bleeding, or assessing acute abdominal pain. They are also valuable in cancer staging and monitoring treatment progress.

Advancements in CT Technology: Improving Patient Care

Continuous innovations in CT technology have led to improved image quality, reduced radiation exposure, and expanded diagnostic capabilities.

Recent Developments in CT Scanning

• Dual-energy CT: Provides enhanced tissue characterization
• Spectral CT: Allows for better material differentiation
• Low-dose CT protocols: Minimize radiation exposure
• Artificial intelligence integration: Improves image reconstruction and analysis
• 4D CT imaging: Captures movement over time for dynamic studies

How do these advancements benefit patients? These technological improvements result in more accurate diagnoses, reduced radiation exposure, faster scan times, and the ability to detect subtle abnormalities that might have been missed with older CT systems. This leads to earlier detection of diseases and more personalized treatment plans.

CT Scan Procedure: What to Expect During the Examination

Understanding the CT scan procedure can help alleviate anxiety and ensure a smooth examination experience for patients.

Steps in a Typical CT Scan

1. Patient preparation and positioning on the CT table
2. Administration of contrast media (if required)
3. Table movement into the CT scanner
4. Brief breath-holding instructions during image acquisition
5. Multiple scans taken as the table moves through the scanner
6. Review of images by the radiologist

How long does a CT scan typically take? Most CT scans are completed within 10 to 30 minutes, depending on the area being examined and whether contrast media is used. The actual scanning time is often just a few minutes, with the remaining time devoted to patient positioning and preparation.

Post-Scan Care and Results

After the CT scan, patients can usually resume their normal activities immediately. If contrast media was used, drinking plenty of water helps flush it out of the system. The radiologist will analyze the images and send a report to the referring physician, who will discuss the results with the patient.

When can patients expect to receive their CT scan results? The timing of results can vary depending on the facility and the urgency of the case. In emergency situations, results may be available within hours. For routine scans, it typically takes a few days for the radiologist to interpret the images and send a report to the referring physician.

Ensuring CT Scan Safety: Precautions and Considerations

While CT scans are generally safe, certain precautions and considerations are essential to minimize risks and ensure optimal patient care.

Radiation Safety Measures

• Use of lead shielding for sensitive areas
• Tailoring scan parameters to patient size and age
• Implementing dose reduction techniques
• Regular equipment maintenance and calibration
• Adhering to ALARA (As Low As Reasonably Achievable) principle

How do healthcare providers minimize radiation exposure during CT scans? Radiologists and technologists use various strategies to reduce radiation dose while maintaining image quality. These include adjusting scan parameters, using iterative reconstruction techniques, and implementing dose modulation software.

Special Considerations for Specific Patient Groups

Certain patient populations require special attention when undergoing CT scans:

• Pregnant women: CT scans are generally avoided unless absolutely necessary
• Children: Pediatric protocols are used to minimize radiation exposure
• Patients with kidney problems: Alternative imaging methods may be considered
• Individuals with contrast allergies: Pre-medication or non-contrast scans may be recommended

What alternatives are available for patients who cannot undergo CT scans? Depending on the diagnostic needs, alternatives may include MRI, ultrasound, or nuclear medicine studies. In some cases, modified CT protocols or the use of alternative contrast agents may be considered.

The Future of CT Scanning: Emerging Technologies and Applications

The field of CT imaging continues to evolve, with new technologies and applications expanding its diagnostic capabilities and improving patient care.

Emerging CT Technologies

• Photon-counting CT: Offers improved spatial resolution and material differentiation
• Ultra-high resolution CT: Provides microscopic-level imaging
• Phase-contrast CT: Enhances soft tissue visualization
• Hybrid imaging systems: Combine CT with other modalities like PET or SPECT

How will these advancements impact patient care? These emerging technologies promise to deliver more detailed and accurate imaging, potentially leading to earlier disease detection, improved treatment planning, and reduced need for invasive procedures. They may also enable new applications in fields such as material science and industrial imaging.

Expanding Applications of CT Imaging

CT technology is finding new applications beyond traditional diagnostic imaging:

• 3D printing of anatomical models for surgical planning
• CT-guided interventional procedures
• Quantitative imaging for tissue characterization
• Functional CT imaging for organ perfusion studies
• CT-based virtual reality applications for education and training

What role will artificial intelligence play in the future of CT imaging? AI is expected to revolutionize CT imaging by improving image reconstruction, automating analysis, and assisting in diagnosis. This could lead to faster scan times, reduced radiation dose, and more accurate and consistent interpretations.

As CT technology continues to advance, it remains a cornerstone of modern medical imaging, providing invaluable insights into the human body and supporting improved patient outcomes across a wide range of medical specialties.

Computed Tomography (CT) Scan | Johns Hopkins Medicine

What You Need to Know

• A CT scan is a diagnostic imaging exam that uses X-ray technology to produce images of the inside of the body.
• A CT scan can show detailed images of any part of the body, including the bones, muscles, organs and blood vessels.
• CT scans can also be used for fluid or tissue biopsies, or as part of preparation for surgery or treatment.
• CT scans are frequently done with and without contrast agent to improve the radiologist’s ability to find any abnormalities.

What is a CT scan?

Computed tomography is commonly referred to as a CT scan. A CT scan is a diagnostic imaging procedure that uses a combination of X-rays and computer technology to produce images of the inside of the body. It shows detailed images of any part of the body, including the bones, muscles, fat, organs and blood vessels.

CT scans are more detailed than standard X-rays. In standard X-rays, a beam of energy is aimed at the body part being studied. A plate behind the body part captures the variations of the energy beam after it passes through skin, bone, muscle and other tissue. While much information can be obtained from a regular X-ray, a lot of detail about internal organs and other structures is not available.

In CT, the X-ray beam moves in a circle around the body. This allows many different views of the same organ or structure and provides much greater detail. The X-ray information is sent to a computer that interprets the X-ray data and displays it in two-dimensional form on a monitor. Newer technology and computer software makes three-dimensional images possible.

CT scans may be performed to help diagnose tumors, investigate internal bleeding, or check for other internal injuries or damage. CT can also be used for a tissue or fluid biopsy.

Why are CT scans sometimes ordered with contrast?

CT scans may be done with or without contrast. Contrast refers to a substance taken by mouth or injected into an IV line that causes the particular organ or tissue under study to be seen more clearly. Contrast examinations may require you to fast for a certain period of time before the procedure. Your doctor will notify you of this prior to the procedure.

You will need to let your doctor know if you have ever had a reaction to any contrast media and/or any kidney problems. A reported seafood allergy is not considered to be a contraindication for iodinated contrast. If you have any medical conditions or recent illnesses, inform your doctor.

How do I prepare for a CT scan?

If you are having a computed tomography angiography (CTA) or a virtual colonoscopy, you will be given specific instructions when you make your appointment.

PRECAUTIONS: If you are pregnant or think you may be pregnant, please check with your doctor before scheduling the exam.

CLOTHING: You may be asked to change into a patient gown. If so, a gown will be provided for you. Please remove all piercings and leave all jewelry and valuables at home.

CONTRAST MEDIA: Contrast may be indicated for your exam. The contrast media improves the radiologist’s ability to find structures that are abnormal and understand normal anatomy better.

• Some patients should not have an iodine-based contrast media. If you have problems with your kidney function, please inform your radiologist in advance. We may be able to perform the scan without the contrast media or find an alternate imaging exam.
• The most common type of CT scan with contrast is the double-contrast study, which will require you to drink a contrast media before your exam begins in addition to the IV contrast. The more contrast you are able to drink, the better the images are for the radiologist to visualize your digestive tract.

ALLERGY: Please inform the access center representative when you schedule your scan if you have had an allergic reaction to any contrast media. IV contrast will not be administered if you have had a severe or anaphylactic reaction to any contrast media in the past. Mild to moderate reactions warrant a plan that includes taking medication prior to the CT examination. These plans will be discussed with you in detail when you schedule your exam. Any known reactions to a contrast media should be discussed with your personal physician.

EAT/DRINK: If your study was ordered without contrast, you can eat, drink and take your prescribed medications prior to your exam.

If your doctor orders a CT scan with contrast, do not eat anything three hours prior to your CT scan. We encourage you to drink clear liquids. You may also take your prescribed medications prior to your exam.

DIABETICS: People with diabetes should eat a light breakfast or lunch three hours prior to the scan time. Depending on your oral medication for diabetes, you may be asked to discontinue use of the medication for 48 hours after the CT examination. Detailed instructions will be given following your examination.

MEDICATION: All patients can take their prescribed medications as usual.

The Newest CT: Faster Than a Heartbeat

A new CT scanner will change the management and outcomes of coronary artery disease. The CT scan captures images of the heart between beats, leading to clearer images to help detect anatomic and functional characteristics of coronary artery disease. This technology can also be used to help replace invasive tests to determine which patients with chest pain need intervention.

Read more

What are the risks of a CT scan?

If you are pregnant or think you may be pregnant, you should notify your health care provider.

The amount of radiation dose used in a CT scan is small. You may want to ask your doctor about the amount of radiation used during the CT procedure and the risks related to your particular situation.

If you are claustrophobic or tend to become anxious easily, tell your doctor ahead of time. You may be prescribed a mild sedative to take before the procedure to make you more comfortable.

What happens during a CT scan?

CT scans may be performed on an outpatient basis or as part of your stay in a hospital. Procedures may vary depending on your condition and your physician’s practices. Generally, CT scans follow this process:

• You may be asked to change into a patient gown. If so, a gown will be provided for you. A locker will be provided to secure all personal belongings. Please remove all piercings and leave all jewelry and valuables at home.
• If you are to have a procedure done with contrast, an IV line will be started in the hand or arm for injection of the contrast media. For oral contrast, you will be given a liquid contrast preparation to swallow. In some situations, the contrast may be given rectally.
• You will lie on a scan table that slides into a large, circular opening of the scanning machine.
• The technologist will be in another room where the scanner controls are located. However, you will be in constant sight of the technologist through a window. Speakers inside the scanner will enable the technologist to communicate with and hear you. You may have a call button so that you can let the technologist know if you have any problems during the procedure. The technologist will be watching you at all times and will be in constant communication.
• As the scanner begins to rotate around you, X-rays will pass through the body for short amounts of time. You will hear clicking sounds, which are normal.
• The X-rays absorbed by the body’s tissues will be detected by the scanner and transmitted to the computer. The computer will transform the information into an image to be interpreted by the radiologist.
• It is important that you remain very still during the procedure. You may be asked to hold your breath at various times during the procedure.
• If contrast media is used for your procedure, you may feel some effects when the contrast is injected into the IV line. These effects include a flushing sensation, a salty or metallic taste in the mouth, a brief headache, or nausea and/or vomiting. These effects usually last for a few moments.
• You should notify the technologist if you have any breathing difficulties, sweating, numbness or heart palpitations.
• When the procedure has been completed, you will be removed from the scanner.
• If an IV line was inserted for contrast administration, the line will be removed.
• While the CT procedure itself causes no pain, having to lie still for the length of the procedure might cause some discomfort or pain, particularly in the case of a recent injury or invasive procedure, such as surgery. The technologist will use all possible comfort measures and complete the procedure as quickly as possible to minimize any discomfort or pain.

What happens after a CT scan?

• If contrast media was used during your procedure, you may be monitored for a period of time for any side effects or reactions to the contrast, such as itching, swelling, rash or difficulty breathing.
• If you notice any pain, redness and/or swelling at the IV site after you return home following your procedure, you should notify your doctor, as this could indicate an infection or other type of reaction.
• There is typically no special type of care required after a CT scan. You may resume your usual diet and activities unless your doctor advises you differently.
• Your doctor may give you additional or alternate instructions after the procedure, depending on your particular situation.

What are some of the advances in CT technology?

Advances in CT technology include:

• High-resolution CT: This type of CT scan uses very thin slices (less than 0. 1 inches), which are effective in providing greater detail in certain conditions, such as lung disease.
• Helical or spiral CT: During this type of CT scan, both the patient and the X-ray beam move continuously, with the X-ray beam circling the patient. The images are obtained much more quickly than with standard CT scans. The resulting images have greater resolution and contrast, providing more detailed information. Multidetector-row helical CT scanners may be used to obtain information about calcium buildup inside the coronary arteries of the heart.
• Ultrafast CT (also called electron beam CT): This type of CT scan produces images very rapidly, thus creating a type of “movie” of moving parts of the body, such as the chambers and valves of the heart. This scan may also be used to obtain information about calcium buildup inside the coronary arteries of the heart, but the helical scanners are much more common.
• Computed tomographic angiography (CTA): Angiography (or arteriography) is an X-ray image of the blood vessels. A CT angiogram uses CT technology rather than standard X-rays or fluoroscopy to obtain images of blood vessels — for example, the coronary arteries of the heart.
• Combined positron emission tomography and CT (PET/CT): The combination of CT and positron emission tomography technologies into a single machine is referred to as PET/CT. PET/CT combines the ability of CT to provide detailed anatomy with that of PET to show cell function and metabolism in order to offer greater accuracy in the diagnosis and treatment of certain types of diseases, particularly cancer. PET/CT may also be used to evaluate conditions such as epilepsy, Alzheimer’s disease and coronary artery disease.

Purpose, Procedure, Risks, Side-Effects, Results

Written by WebMD Editorial Contributors

• How Do CT Scans Work?
• How Are CT Scans Done?
• What Is It Used For?
• What Is a CT Scan with Contrast?
• Are There Any Risks?
• What Are the Side Effects?
• More

A computed tomography (CT or CAT) scan allows doctors to see inside your body. It uses a combination of X-rays and a computer to create pictures of your organs, bones, and other tissues. It shows more detail than a regular X-ray.

You can get a CT scan on any part of your body. The procedure doesn’t take very long, and it’s painless.

They use a narrow X-ray beam that circles around one part of your body. This provides a series of images from many different angles. A computer uses this information to create a cross-sectional picture. Like one piece in a loaf of bread, this two-dimensional (2D) scan shows a “slice” of the inside of your body.

This process is repeated to produce a number of slices. The computer stacks these scans one on top of the other to create a detailed image of your organs, bones, or blood vessels. For example, a surgeon may use this type of scan to look at all sides of a tumor to prepare for an operation.

You’d probably get a scan at a hospital or radiology clinic. Your doctor might tell you not to eat or drink for a few hours before the procedure. You may also need to wear a hospital gown and remove any metal objects, such as jewelry.

A radiology technologist will perform the CT scan. During the test, you’ll lie on a table inside a large, doughnut-shaped CT machine. As the table slowly moves through the scanner, the X-rays rotate around your body. It’s normal to hear a whirring or buzzing noise. Movement can blur the image, so you’ll be asked to stay very still. You may need to hold your breath at times.

How long the scan takes will depend on what parts of your body are being scanned. It can take anywhere from a few minutes to a half-hour. In most cases, you’ll go home the same day.

Doctors order CT scans for a long list of reasons:

• CT scans can detect bone and joint problems, like complex bone fractures and tumors.
• If you have a condition like cancer, heart disease, emphysema, or liver masses, CT scans can spot it or help doctors see any changes.
• They show internal injuries and bleeding, such as those caused by a car accident.
• They can help locate a tumor, blood clot, excess fluid, or infection.
• Doctors use them to guide treatment plans and procedures, such as biopsies, surgeries, and radiation therapy.
• Doctors can compare CT scans to find out if certain treatments are working. For example, scans of a tumor over time can show whether it’s responding to chemotherapy or radiation.

In a CT scan, dense substances like bones are easy to see. But soft tissues don’t show up as well. They may look faint in the image. To help them appear clearly, you may need a special dye called a contrast material. They block the X-rays and appear white on the scan, highlighting blood vessels, organs, or other structures.

Contrast materials are usually made of iodine or barium sulfate. You might receive these drugs in one or more of three ways:

• Injection: The drugs are injected directly into a vein. This is done to help your blood vessels, urinary tract, liver, or gallbladder stand out in the image.
• Orally: Drinking a liquid with the contrast material can enhance scans of your digestive tract, the pathway of food through your body.
• Enema: If your intestines are being scanned, the contrast material can be inserted in your rectum.

After the CT scan, you’ll need to drink plenty of fluids to help your kidneys remove the contrast material from your body.

CT scans use X-rays, which produce ionizing radiation. Research shows that this kind of radiation may damage your DNA and lead to cancer. But the risk is still very small — your chances of developing a fatal cancer because of a CT scan are about 1 in 2,000.

But radiation’s effect adds up over your lifetime. So your risk increases with every CT scan you get. Talk to your doctor about the procedure’s potential dangers and benefits, and ask why the CT scan is necessary.

Ionizing radiation may be more harmful in children. That’s because they’re still growing. They also have more years to get exposed to radiation. Before the procedure, you may want to ask the doctor or technician if the CT machine’s settings have been adjusted for a child.

Tell your physician if you’re pregnant. If you need imaging for your stomach area, your doctor may recommend an exam that doesn’t use radiation, such as an ultrasound.

Some people are allergic to the contrast materials. Most of the time, the reaction is mild. It can lead to itchiness or a rash. In very few cases, the dye may trigger a life-threatening reaction. For this reason, your health care provider may want to monitor you for a short period after your CT scan. Tell your doctor about any allergies you have to medications, seafood, or iodine.

Your doctor should know, too, if you have diabetes and are taking the drug metformin. They’ll let you know if you should stop taking your medication before or after your procedure.

Although it’s rare, contrast materials can lead to kidney problems. Let your doctor know if you have any kidney issues before the CT scan.

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Kinematic laser scanning for urban land use and utility infrastructure assessment

Urbanization and the development of megacities pose serious challenges for sustainable but efficient land use around the world. Power lines, pipelines for water, district heating, gas and oil, and other technological systems are critical but often hidden features that make modern life easier. Meanwhile, there is an ongoing need to preserve natural environments and recreational spaces in the world’s cities, despite the need to lay more concrete and asphalt to accommodate the people and businesses flocking to them. This article looks at how kinematic laser scanning can contribute to urban planning and infrastructure management.

The need for more efficient use of the limited urban area is constantly increasing. This is driving the development and use of 3D information systems, such as in cadastre, land-use planning and utility management, as well as in surveying and documentation technologies, to provide high quality 3D and graphical data to meet such needs. Knowing the exact location of infrastructure is important to ensure smooth operation so that you can plan and manage the construction of new pipelines, data cables, power cables, etc., as well as upgrade old systems and maintain and expand urban green spaces. If such data and information systems are accurate and up-to-date, all work can be completed faster, minimizing or eliminating unnecessary disruptions. At the same time, urban space can be used more efficiently to support various utilities, traffic and domestic needs.

Multi-modal (i. e., performed in multiple ways) laser scanning data is increasingly being used for surveying and cartography due to the development and availability of high-performance sensor technologies. Small but powerful laser scanning and imaging systems solve application problems using virtually any platform for laser scanning, from which data are subsequently solved for 3D reconstruction problems. Airborne kinematic laser scanning systems and devices on vehicles, backpacks and portable mapping systems can serve as a means of collecting additional data for various user needs and specifications.

3D point clouds provide a common starting point for automated modeling workflows and the creation of visualization and measurement applications, shaping the future topobase. They are an important asset for business and administration, especially in forestry, infrastructure management, and urban planning. They are also the basis for the development of solutions for future applied problems.

Calibration of a point cloud in an urban environment using a mobile laser scanning system to create a digital twin of the urban environment. In order to convert raw positioning and laser scan data into an accurate point cloud, it is necessary to calibrate the system offsets and sensor rotation axes – in this case, for this, planar elements are used that are automatically found in this survey area.

Kinematic laser scanning

Developments in laser scanning and point cloud processing can provide significant cost savings by automating the processing of data sets with improved output and detail. The collection of kinematic data is provided mainly by two different technologies: GNSS-IMU positioning and simultaneous localization and mapping (SLAM), both of which are means of tracking the movements of geodetic laser scanners during operation. The former provides data in the global geographic coordinate system, while the latter typically provides data in the local coordinate system.

What makes the use of laser scanning in mapping so effective is the ability to take 3D measurements of any object within the line of sight of the laser beam. To obtain information about the coordinates of reflections, the principles of laser ranging are used. The range measurement method consists in transmitting short but powerful laser pulses at high speed towards the subject and collecting the backscatter signal. The signal is then processed to detect objects at various distances within the beam illumination area. With the help of positioning on the trajectory, data synchronization and calibration of the aiming system, the received information is processed into usable three-dimensional data. An important end product of such surveys is a point cloud, where the location of each point is known in a local or geographic coordinate system. Such data enables instant visualization and measurement, but more often the user needs more generalized materials: virtual models and terrain models.

Drone data (suburban areas) can be used to assess land use and update urban planning and cadastre. High-resolution laser reflectance information provides insight into surface materials and helps to separate and identify objects.

Urban land use assessment

Urban land management is becoming increasingly important to ensure sustainable development and promote safe and prosperous communities and environments in ever-growing agglomerations and metropolitan areas. In general, the entire urban space can be divided into residential, business and public areas, transport facilities, parks, recreational and natural environment and communal facilities. All of this needs to be managed somehow.

Modern laser scanning technologies make it possible to map complex urban space in various ways, both from the air and from the ground. In general, airborne laser scanning, often supported by aerial photographs, is a versatile data source for large-scale terrain and building assessments. This allows a variety of tools to be used to detect new buildings and roads, monitor landfills, earthworks, illegal constructions, deforestation and other similar low-detail indicators, typically with an accuracy level of 10-50 cm.

Recreational space around an apartment building mapped using kinematic laser scanning. The data provide an accurate description of land use and construction sites. Dense point cloud data also enables fast visualization.

For more detailed control and especially for planning purposes, higher accuracy and resolution is desirable. For example, a more accurate estimate of backfill/excavation volume before a road or building is constructed can allow contractors to reduce costs, and even more so if they can track the progress of earthworks/excavations in near real time to control excavation and manage a truck fleet. It can also allow you to adjust the design of the final surface on the object after the end of construction (if necessary).

High-resolution laser scan data can be obtained from the air using unmanned aerial vehicles (UAVs or “drones”). Aerial scanning provides easy access to objects with obstacles such as fences, trenches and construction sites, and also allows you to take pictures of the condition of building roofs, power lines, and so on. Typically, instruments also provide more accurate measurements than those used at high altitudes, and data densities typically range from 50 to hundreds of points per square meter. Based on such data, various elements of the urban environment can be examined in detail: streets, curbs, ramps, outlines and heights of buildings, urban green spaces and soil cover, playgrounds, bridges and culverts, and much more.

3D kinematic data not only allows you to quickly document the construction phase, but also allows you to track land use, terrain and drainage height, as well as check the level of the building foundation and the placement of the structure against permits and the city plan.

Aerial (drone) survey data can be supplemented or replaced with ground survey data using Mobile Laser Scanning (MLS) systems. These systems can be moved using wheeled vehicles, and these data typically provide detailed mapping of street sections of interest. In some cases, smaller vehicles can be used to access restricted urban spaces. Alternatively, a backpack or portable tools can be used to obtain the data needed to complete the task at hand. Such data can typically cover interior areas, recreation areas, playgrounds, and parks, and provide a high level of detail in the mass of buildings, walkways, street layouts, and utilities.

Construction monitoring

Monitoring of construction activities is one of the key areas of interest for the city administration. Kinematic laser scanning data allows you to get a complete picture of the placement of the structure, the levels of the foundation, the location of the object in relation to the surrounding area, streets, and drainage systems.

From a builder’s and contractor’s perspective, laser scanning is an excellent tool for documenting construction progress and placing foundations or structural elements before moving on to the next phase of construction. Accurate data allows you to control the dimensions and adapt the design of prefabricated elements, which saves costs and minimizes delays.

From a safety and accessibility point of view, accurate 3D data allows you to plan and manage the use of space on a site to design areas for lifting, storage and movement. This data also makes it possible to document on-site protections such as fences and detours and traffic past the site. Such data can then be passed on to the city or road authority to report on work plans or potential impacts on traffic.

Earthworks and blasting at a construction site with a new building foundation.

Infrastructure documentation

Public and private infrastructure provides settlements with everyday resources (which are often taken for granted in urban life). These are electricity, water and heating, not to mention functional transport systems with roads, streets and related facilities. Maintaining this infrastructure to ensure its smooth operation requires effort and cost, which can be minimized through the use of modern asset management technologies. Up-to-date and accurate databases of 3D objects, supported by geodetic technologies that provide accurate 3D data, help prevent collateral damage during excavation and can be used to share asset information between contractors and other parties involved in any given construction.

Overhead cables are an important feature of any urban landscape as well as electric railways. They occupy space above urban areas, hang over streets and cut through parks and forests. Kinematic laser scanning is particularly suitable for corridor-type surveys, and power lines are well-defined corridor-type objects. Kinematic laser scanning provides ease of deployment and data collection with good accuracy and level of detail for modeling and monitoring of above ground objects. Mapping is not limited to the power line itself, but also provides accurate information about the terrain and vegetation in the immediate vicinity of the line. Off-road, mobile scanning in the desired corridor can be achieved by using all-terrain vehicles or by deploying a special laser scanning system in the form of a backpack with a laser scanner for work in difficult terrain. The main advantages of MLS (Mobile Laser Scanning) over Airborne Laser Scanning (ALS) are higher detail (due to less distance to objects of interest), less need for experienced maintenance personnel, and overall operability in difficult weather conditions (for example, in strong wind or rain).

Installation of underground pipeline for district heating. With kinematic laser scanning, the location of the containment box can be documented for future maintenance and repair planning.

Underground structures such as power cables, water and gas pipes, sewers, drainage pipelines, and district heating pipelines are usually laid underground to increase space efficiency, but often also to improve safety and ensure uninterrupted delivery. However, this poses a risk of damage and destruction if the exact location and depth of the installation is not well documented and new construction needs to be done in the area or, for example, there is a pipeline leak. Such documentation is possible using kinematic laser scanning, and the range of laser scanners does not require the imaging system to be located directly at the excavation zone, which increases the safety of the team and speeds up the process. In one pass, the surveyor can capture the laying object itself (cable, pipe), the surrounding earthworks and the general geometry of the objects of interest with a high degree of detail. Later, back at the office, the current status of the underground facilities, the location of the technical components and the main piping can be transferred to a database for distribution and future use. This application is often found in industrial facilities with complex piping and distribution installations.

A longitudinal section of the pipeline shows the location of the welds and seam insulation, the slope of the pipe and the position in depth relative to the earth backfill.

Output

The application of kinematic laser scanning in urban environments provides detailed information for many purposes related to the management, development and documentation of human activities and interactions with nature and terrain. The collection of kinematic data using laser scanning, whether based on GNSS-IMU or SLAM, allows you to quickly capture the geometry and condition of objects without disrupting operation, and captures precise dimensions and relationships between objects that are not always available using conventional surveying tools. With the help of kinematic laser scanning data, the actual state, construction phase and location of the components of the urban environment can be digitized, or the entire site can be surveyed and documented in 3D. Mapping and documenting the various uses of the urban environment, land cover, landscape features and vegetation are important applications for kinematic laser scanning in urban environments. This allows the use of these materials in the future for more rational planning of urban space and land use.

Railroad structures captured by a portable mobile system form the point cloud needed for asset documentation and modeling. The exact location of rails, supports, portals, wires and insulators, cable ducts and balancers is clearly visible, most objects are identified by an accurate point cloud.

High-resolution laser scanning data from aerial drone surveys of an urban area provide a detailed 3D picture of space usage and update the city plan.

Laser scanning – engineering and geodetic surveys

Nakor-K Company performs all types of laser scanning in any geographical and weather conditions, in open spaces and in enclosed spaces, from air and water.

Principle of laser scanning

Laser scanning measures the distance from the source of a laser pulse to a desired point on an object. Further, the laser beam emitted by the emitter is reflected from this point and already reflected is received by the scanner receiver. Then either the time delay (impulse method) or the phase shift (phase method) between the signal that was emitted and the reflected signal that was received is evaluated. This evaluates the distance to the point. Further, according to the data received from the scanner, the position of the point in space, that is, its coordinates, is determined.

The laser scanner can generate measuring pulses at an enormous frequency – several hundred thousand per second. These pulses are evenly distributed over the surface of the measured object. Sometimes a system of movable mirrors is used for uniformity. Thus, from one scanner, an array of coordinate points is obtained, reflecting all the spatial parameters of the object. When shooting from several points, several data fields are obtained, when combined, a single array of points for the object is formed.

Based on these points, a three-dimensional laser model is built that repeats the object.

Types of laser scanning

Depending on the tasks to be solved, laser scanning can be terrestrial, airborne or mobile. Each type of laser shooting is designed to solve certain problems in certain conditions.

In progress:

• survey in built-up areas or wide sparsely populated areas;
• filming of industrial objects, outside and inside;
• survey at various stages of construction;
• shooting from moving objects;
• shooting from air or water, etc.

Depending on the complexity of the object, the type and scope of work, altitude and other parameters, Nakor-K specialists will determine the optimal type of scanning for each object.

Ground laser scanning

Scanning is carried out from the ground: from the ground or from a ground object, in discrete mode. This type of scanning is applicable both in open spaces and indoors, it is suitable for complex objects, open and closed spaces.

As a result of ground survey, you can get a 3D model of an object, a facade plan, a topographic plan. The scope of this type of research is quite wide.

The scanner is installed at a point whose coordinates are known, after which the scanner captures object data. Shooting can be done from several points, it is sometimes necessary to obtain complete spatial information on the object. After that, the obtained point clouds are combined into a single array with the creation of a three-dimensional model of the object.

Scanner range from 1 to n*100 m, resolution n*1mm.

Mobile laser scanning

This type of survey is made from a mobile carrier on land or water, hence the name. Supporting scanning methods are intended mainly for shooting in open space, but short -term stay in a closed environment is allowed: for example, travel under the bridge, in the tunnel, entry into the arch, etc.

Mobile removal of points are used when shooting in settlements, cities in order to cartography and linear modeling of the city’s infrastructure: the location etc. The method is good for complex infrastructure objects such as multi -level roads. When shooting from a boat, it is possible to fix the coast, the type of coastline, coastal cliffs, downstream locks, dams, hydroelectric power stations, etc.

Compared to close-to-mobile aerial photography, when shooting from a mobile carrier located close to the ground, there is a problem that the GPS receiver is in the shadow of the signal from the satellites due to buildings, trees and other objects. Nevertheless, this method is successfully used when surveying roads, bridges, streets and other infrastructure elements.

Airborne laser scanning

Shooting is carried out from an aircraft in continuous mode. The scanner is installed on an airplane, helicopter, on an unmanned aerial vehicle such as a quadrocopter. The method is effective for surveying large areas in a relatively short period of time. On the aircraft, in addition to the scanner, a GPS receiver and an IMU inertial system are installed to measure the spatial position of the scanner in real time.

The use of aerial laser scanning is optimal for areal surveys, as well as for surveying extended linear infrastructure elements – pipelines, etc. But for surveying large areas, the method is optimal.

It should be noted that several methods are often used at once in order to obtain the most accurate picture of the object and to minimize the shortcomings with such an integrated approach.

Results of laser scanning

Based on the results of scanning, the customer receives information about a given object, which can be expressed in the following types of documents:

• digital models of the object, topographic plans of the area;
• three-dimensional models in formats: CAD, 3D MAX, DGN;
• sections, sections, profiles of an object;
• facade plans;
• floor plans;
• orthophotos;
• “mesh” model of the object, this is relevant for architectural monuments with a complex structure, stucco molding, etc.