The fastest, most affordable, and most accurate surveying method available today
The margin of error of the 3D Point Cloud provided by the Meissa Platform is 2-3 cm on the x and y axes and up to 6 cm on the z axis compared to ground-truth values (the same coordinates measured with a GPS instrument). However, during analysis the z-axis error is also corrected to around 2-3 cm, resulting in an earthwork volume error of about 0.5%.
The biggest reason to use the Meissa Platform on active construction sites is its innovation in construction surveying. After ground is broken, you can check at a glance-intuitively or quantitatively-whether the positions of structures and the earthwork volumes specified in the design drawings match reality. Before the Meissa Platform was introduced, you had to carry a GPS instrument across a vast site to capture coordinates, then return to the office to enter the data into CAD and Excel. Now a single drone flight can replace this entire process. And it is even more accurate.
There is no need to capture the site's countless chains one by one every time. A single input of an earthwork cross-section line derives the change values for every cross-section, and you can export them to Excel if needed.
Place your CAD drawings over a high-resolution map (orthophoto) that captures the most up-to-date conditions to track progress. You can also take real measurements with the map tool.
The Meissa Platform uses general-purpose aircraft rather than expensive specialized drones. Even after adding the cost of the aircraft, the monthly subscription, and other add-on services, you can obtain more deliverables at only about 10% of the cost and time of conventional methods. You can find more details about the improved workflow at actual sites in this article.
You can also perform 'repeat surveys' on your own at the site to raise construction accuracy and reduce defects, and all of these site conditions are stored securely on cloud servers.
At actual sites today, earthwork volume is usually calculated using GPS-instrument surveying and the average-end-area method rather than LiDAR. This inevitably simplifies the volume calculated between survey points, and the larger the site, the farther apart the survey points become. On this note, we share research findings showing that the smaller the chain interval, the closer the result gets to the drone-based earthwork volume estimate.
Field applicability of drone-based earthwork volume estimation <Joint research by the Korea Institute of Civil Engineering and Building Technology, Meissa, and Sahmyook University>
The joint research team published a paper studying the field applicability of drone-based earthwork volume estimation. Through this paper, they experimentally proved that earthwork volume estimation using a DSM derived from drone data can produce more accurate and efficient results than conventional GPS surveying. According to the findings, drone-based earthwork volume estimation can produce more accurate results than conventional chain-based earthwork volume estimation. They confirmed that the difference between DSM-based and chain-based earthwork volume remained below 5.3% until the chain interval decreased to 5 m. This means that the closer the chain interval gets to 5 m, the closer the DSM-based earthwork volume gets to the actual earthwork volume.
The images above show 3D Point Cloud models created with LiDAR (left) and a drone (right). LiDAR measures the position of an object's surface by detecting the reflection of light wavelengths, while 3D Reconstruction analyzes overlapping 2D images to extract the elevation values of an object's surface. The principles differ, but the results are similar in form; the 3D-reconstructed model projects the RGB color values of the photos directly onto the points, giving it a more intuitive appearance.
LiDAR surveying is commonly believed to be far more accurate. However, in the case of commercial drone LiDAR (the DJI ZENMUSE L2 model) rather than terrestrial LiDAR (with a mm-level error rate), the error value is confirmed to be 4.5 cm (4 cm vertical accuracy, 5 cm horizontal accuracy). Even considering that this figure is stated generously due to environmental and analysis-software variables, the typical drone surveying error range is 1-2 cm horizontal and 6 cm vertical (1-3 cm after correction), so there is no dramatic difference.
On this note, we attach the results of a general-purpose rotary-wing aircraft surveying experiment conducted at an actual DL E&C site in 2018. As for the comparison between LiDAR sensors and photogrammetry, in the following article we will explain it in more detail.
● Using 3D Point Clouds on the Meissa Platform
| Creating cross-sections (current elevation) and elevation surveying
| Automatic earthwork volume calculation feature
| Using planned elevation and stratum elevation
| 3D Point Cloud and BIM data overlay
