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Is LIDAR or Photogrammetry Ideal for As-Built Surveys?








Drone photogrammetry is a rapidly growing technology in the field of surveying that offers numerous benefits over LIDAR as well as some drawbacks. In this article, we will explore the pros and cons of using drone photogrammetry for surveying, to help you understand its potential and limitations.


Why is Photogrammetry great?




Accuracy: Drone photogrammetry provides high accuracy measurements with error in the range of 2-3 cm, which is on par with traditional ground-based surveys. The use of advanced imaging sensors and high precision GPS technology results in precise measurements, making it ideal for surveying large areas, complex terrains, and hard-to-reach locations.


Cost-effectiveness: Drones can cover large areas in a relatively short amount of time, which results in significant cost savings compared to traditional surveying methods. Drones are also more cost-effective in terms of equipment, as they are relatively low-cost and can be easily maintained and repaired. LIDAR equipment is much more expensive than photogrammetry. Photogrammetry provides a high accuracy solution that can also be very cost effective.


Faster Data Collection: Drone photogrammetry allows for faster data collection compared to traditional surveying methods. The speed of data collection results in a more efficient process, reducing project timelines and allowing for quicker decision making. Less time in the field also reduces overall cost, meaning projects can be turned faster and cheaper than before.


Build products after the fact: With traditional methods, if the customer finds that they need more information on a specific area after the fact, the survey crew needs to make another trip. Drone mapping saves a complete record of site conditions. This means that any question a customer may have can be answered after the fact within minutes of work on the computer.



Where are drones limited


Weather Dependent: Drone photogrammetry is weather dependent and cannot be performed in adverse weather conditions, such as heavy rain, snow, or high winds. This can cause significant delays in the surveying process and result in rescheduling and additional costs.


Technical Skills Required: Drone photogrammetry requires a certain level of technical skill to operate and interpret the data, which may limit its use to those with the necessary training and experience. This can increase costs, as specialized personnel are needed to operate and interpret the data.


Lidar vs Photogrammetry



Drone photogrammetry and lidar are two different technologies used in the field of surveying. While both technologies can be used to create high-resolution maps and three-dimensional models, they have some distinct differences.


Drone photogrammetry involves using a drone equipped with a high-resolution camera to take photographs of an area. These images are then processed using software to extract precise measurements and generate a three-dimensional model. Drone photogrammetry is a cost-effective solution for large-scale mapping and is ideal for mapping complex or hard-to-reach terrains, as well as for monitoring changes over time.


Lidar, on the other hand, uses a laser rangefinder to measure distances to an object or surface. This technology works by emitting a laser beam and measuring the time it takes for the beam to return to the sensor after reflecting off the target. Lidar data can be used to create high-resolution maps and three-dimensional models making it ideal for a wide range of applications, including topographic surveys.


One of the main differences between drone photogrammetry and lidar is the type of data they produce. Drone photogrammetry provides a visual representation of the area being surveyed along with a point cloud, while lidar produces only a point cloud. A point cloud is a large set of points in three-dimensional space that represent the surface of the objects in the scene. Both methods are ideal for applications that require detailed topographic information, such as slope analysis, volume calculations, and vegetation mapping. Photogrammetry also produces photographic deliverables that many customers love.


Another difference is their sensitivity to vegetation. Lidar equipment has a limited ability to see through and around some vegetation. Photogrammetry, on the other hand, generally does best with little to no vegetation. Neither technology does well with thick vegetation or dense tree cover. In that case, traditional methods are best.



The choice between drone photogrammetry and lidar for surveying will depend on the specific needs and requirements of each project. Both technologies offer unique advantages and disadvantages, and the best solution will depend on factors such as the type of data required, the accuracy required, the cost, and the specific application.


Pix4D Survey Software

Photogrammetric mapping and surveying using Pix4D survey can provide highly

accurate as-built surveys in certain conditions. A key benefit of this software is the ability to build point, line, and surface features from images. Lidar technology creates a point cloud with no color information. The surveyor has to interpret that point cloud to find features based on shape alone. Pix4D survey allows the surveyor to see all the images that were used to create each point. Each feature can be selected based on where it appears in those images. This allows for a much easier workflow and more accurate feature detection.


In general, photogrammetry can provide high accuracy in mapping and surveying when the images captured by the drone are of sufficient quality. The quality of the images can be influenced by factors such as the resolution of the camera, the lighting conditions, and the drone during flight. The accuracy of the results can also be affected by the flying height and overlap of the images, as well as the processing algorithms used by the software. The higher the flying height and overlap of the images, the greater the accuracy of the results. It is important to have experienced, professional drone pilots in charge of all data collection to ensure the end product is of high quality.


Pix4D survey, specifically, is known for its ability to accurately process drone images into high-resolution maps and 3D models. The software uses advanced algorithms to extract precise measurements and features from the images, and it can accurately handle complex and challenging environments, such as dense forests and urban areas..


Photogrammetric mapping and surveying using Pix4D survey can provide highly accurate as-built surveys in most conditions. Photogrammetry is a cost-effective solution for large-scale mapping and is ideal for monitoring changes over time, but it may not be sufficient for all surveys, depending on the specific requirements of the project, especially for projects with dense vegetation.


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