HOW 3D LASER SCANNING WORKS

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3D Laser scanning also know as HDS Surveying (High Definition Surveying) or LiDAR is a technology that uses lasers to measure and capture environments in 3D. Currently there are many different types of scanners each with varying speeds, accuracies, ranges, durability and general uses. At Digital we operate a fleet of equipment ensuing the best tool is used for the job in hand as no one scanner does everything.

No matter which scanner is used the basic principle is the same. A laser is fired out and for every surface that the laser hits a point in space is recorded (xyz). At the same time the scanner will record the reflectivity of the surface giving an intensity value, and nowadays most scanners also have in built cameras which provide colour and an rgb value to each point.

These points are captured at speeds of up to 1 million points of data per second creating a very dense point cloud of data.

2 Data Capture

All laser scanner work via line of site. This means that on a typical project multiple scans need to be taken from different vantage points to ensure a complete data set. When scanning large objects such as buildings we typically scan at a point density of 3mm at 10m. This means there is a point spacing of 3mm between each point at a distance of 10m from the scanner. As you move further away this spacing increases, so at 20m the distance between each point will have increased to 6mm.

It is very important that the right point density is determined prior to commencing a project. To low a point density will mean key features, edges etc may not be visible in the results.

3 Connecting the Dots

To join multiple scans together a control network needs to be established. This is done by using either targets in the scans, known survey points or by allowing enough overlap in the scans to register by recognising common features (cloud to cloud).

4 Data Download

Back in the office this data is then downloaded, processed & registered together.

5 Creating the 3D Model

Once the data has been downloaded, it is registered and cleaned ready for modelling to take place. Erroneous points or noise can be deleted from the data and it is checked for overall accuracy and compliance with the required project tolerances.

Using specialist plugins the point cloud data is loaded into the modelling software for the project in hand, this could be AutoCAD 3D, Revit, 3DSM, Rhino, Inventor or Solidworks. Our experience modelling team then convert the point data to either a meshed or surfaced 3D model.

Once completed the final model is quality checked one last time against the point cloud, purged of unwanted items and prepared for issue in the clients desired format. If you have a project in mind why not get in touch to see if we can help at: modelling@digitalsurveys.co.uk

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