Last Updated on 23rd May 2022
How do you colourise a point cloud?
More and more sectors are embracing the use of point clouds to help make their surveying and mapping processes quicker, easier, and more efficient. Traditionally used in construction, engineering and geospatial sectors – other industries are starting to see the benefits of point cloud data.
With ever-increasing research and development in the technology, the advances in both scanning hardware and processing software are improving the detail, scale and use of point cloud data. One of these improvements is colourisation. Adding colour has plenty of benefits when viewing and analysing point cloud data, particularly within the AEC sector.
In this article, we’re going to explore what those benefits are, as well as the different ways point cloud colourisation can be achieved. Before we get into the technicalities of colourisation though, we thought we’d start by looking at exactly what point clouds are and how they’re created.
What are Point Clouds?
A very basic definition of a point cloud is a 3D data set of different points in space. Each point is part of a collection that maps a location, object or area. They bring together a large number of separate distance measurements that can be viewed as a whole, such as a 3D object or map.
Standard point clouds are made up of XYZ values, detailing positioning. Colourised point clouds contain RGB values that describe the colours.
How are Point Clouds Created?
Point clouds are created using laser scanners such as TLS (terrestrial laser scanners) or mobile scanning devices.
Laser scanners can register hundreds of thousands of points per second, generating a detailed point cloud. Traditional tripod-based static scanning can create extremely dense point clouds but this requires time and careful scan overlaps. Modern handheld mobile scanners capture point cloud data whilst a user walks through an area, which is much faster.
For more information about point cloud data, take a look at our Point Clouds For Beginners article. For now, we’ll look at the complex questions of colourising point clouds.
Does LiDAR Capture Colour?
Ordinarily, a LiDAR scanner won’t capture colour. Typical LiDAR data includes elevation or intensity values.
Colour-enabled LiDAR scanners could play a big part in the future development of scanning. In the meantime, there are more reliable ways to colourise data during and after capture.
Can LiDAR Point Clouds be Colourised?
In short, yes it can. You can manually assign colour through tagging, you can use photogrammetry data rather than LiDAR to create the point cloud or you can merge together data from both photos and LiDAR point clouds.
Assigning Colour Through Tagging
One way is to assign colour manually, by tagging features of your point cloud. This method is great if you need to highlight specific areas without worrying about realism.
If you need to identify several features, such as trees, pylons or telegraph poles across a site, you can add a tag to them that will change each of these items to a particular colour choice. This makes it stand out, which is particularly useful when it comes to BIM and site planning or revision.
It is possible to semi-automate this process by defining the item generally, or to go through and manually define which items carry a certain colour. However, you will be restricted on how far you can automate this process depending on the software you use and whether it supports this function.
Use Photogrammetry Data
This is the process of creating point clouds using photographic images, rather than LiDAR scanning. To get a point cloud from photos you need a fully comprehensive set of photos, covering every angle of the item or area you’re mapping.
This method is fine for generating rough models that do not need to be particularly accurate. However, this lack of accuracy also rules it unsuitable for many uses, especially when considered alongside the incredible detail and accuracy of a 3D LiDAR point cloud. Photogrammetry also relies on light for it to work. If you were scanning in a dark area you’d still get a dull point cloud.
LiDAR and Photo Data
The most accurate way of colourising point clouds is to merge two sets of data together to get all the detail you need. This can be done manually, by cross-referencing image data with LiDAR data after the fact. There are also more automated options available, depending on your software and hardware options.
Perhaps the most reliable way currently available is to use a camera attachment (such as our new ZEB Vision) with a handheld LiDAR scanner. This allows you to capture photographic and LiDAR data simultaneously. The quality of these cameras is often impressive too, with 360° panoramic images available in 4K definition all collected at the same time as the scans are taken.
These photos are then combined with the LiDAR data to create an incredibly detailed 3D model. The camera and the laser sensor work at exactly the same time so they have identical timestamps. An RGB value is assigned to a point based on timing or distance from the point when captured. The ZEB Vision camera is synced with the ZEB Horizon, so post-processing is an automatic process. This can create an almost pixel-perfect colourised point cloud, and an extremely clear 3D model. Furthermore, our Connect software allows users to do this automatically.
Why Colourise a Point Cloud?
Standard point clouds are incredibly useful tools, but colourisation increases their usability further. Though this reasoning applies in most situations, it is particularly useful in the construction and engineering industries.
Adding colour to a 3D model provides helpful context. Most construction or engineering projects will involve several stakeholders including some who aren’t experienced at reading plans and schematics or are unable to visit a site.
Colourised point clouds give greater realism and clarity. For instance, a fire extinguisher would be easier to spot in a colourised point cloud than in a standard point cloud. It’s purely to help the stakeholders involved better interpret the information provided.
Point cloud data has a wide range of applications for an even wider range of sectors. As its use continues to grow, there will be many more advances that increase its usability, but improved colourisation capabilities are already changing the game.
If you’d like to capture photo-realistic colourised point clouds, then the ZEB Vision is a vital tool for your arsenal. Speak to our team today to find out more about what the combination of a scanner, camera, and easy-to-use SLAM software can do for you.
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