The latest must have capability in the world of terrestrial laser scanners is the capacity for High Dynamic Range. It’s where the equally geeky worlds of Laser Scanning and Photography collide and make it an extra “spoddy” subject to talk about. The principle is pretty simple though.
Most users like to have the option to add colour to the point clouds they generate from their scanners. It makes that fly through of the gothic cathedral more impressive and can help you differentiate between different objects when you’re digitizing their model from the data. A laser scanner on its own however only sees in black and white, and the best you would get is values derived from the intensity of the signal return of the laser. To overcome this most (if not all) scanners have a digital camera installed on board and once the scanner has finished its scan it will spin around again and photograph the same area. The software can then combine the scan data and the photographs to add colour values to each point recorded. Simples you’ve got a gloriously coloured point cloud and scanners have entered the world of digital camera technology!
One of the problems photographers have been dealing with for the past 150 years is high contrast between areas which are very light and very dark. You used to be able to set your camera to record one but not the other, either recording the view outside the window perfectly but everything inside the room is black or the birthday party inside the room is clear but the view outside is a white overexposed blur. With the addition of cameras this problem of high contrast environments now affects the colorization of your scan data. One part of the room is perfectly clear but the far corner is bathed in dark, eerie shadow.
Enter High Dynamic Range! In essence the digital camera captures several versions of the same image using different levels of exposure and it’s the amalgam of these images blended together that you see at the end. You take the view outside the window from one image and blend it with the internal view from another and hey presto you can see the birthday party indoors and the view across the bay outdoors as well. Apply the technique to your scan data and that dark corner of the room is now as clear as the rest.
For some excellent examples and to see what’s possible with the application of technology check out the manufacturer of the iSTAR 360° camera Nstartech’s website
As ever if you want to know more drop us a line at Opti-cal towers.