The Idiot’s Guide to mobile mapping
Is Mobile Mapping the future of Reality Capture?
I’m seeing so many posts on LinkedIn with amazing point cloud videos and what looks like virtual fly-throughs of constriction sites and buildings, but the truth is until now, I had no idea how important it is for the industry or even how it could help me in my field of work, engineering.
This all changed one day when someone gave me an “idiots guide to mobile mapping, laser scanning and point clouds”.
It was only then that I was able to understand the true value of it all.
You might be in a similar position, do you see these wonderful videos and drawings but can’t quite pinpoint how they might help you in your job or even save you time and money?
So this is my gift to you! The idiot’s guide to mobile mapping!
Before we get into the fun stuff, we need to geek out a little. Don’t worry this didn’t hurt my brain too much so you should be fine!
When we talk about mobile mapping, you’ll also hear the terms Lidar and point cloud being used a lot. Lidar is an acronym for light detection and ranging. Now you may have heard of Lidar before, as all new iPhones have it and the way it works is pretty incredible. Lidar works with different types of sensors and lasers to generate 3D Maps. The laser is fired out, hits an object and returns to a sensor, this is calculated (usually either using time of flight, measuring the phase of the beam, or a mixture of both) and converted into a distance measurement. This point (much like a total station) is recorded with a reference to its position. Millions of these points act kind of like pixels in an image, to create the 3D model.
Are you still with me?
Lidar scanners are used to create a point cloud, which is the image/model that is produced featuring these millions of points picked up by the laser. Think of when points are captured for a 2d Survey on a construction site pre, during, and post-construction. Traditionally these points are picked up by a surveyor, we like to call them features (manholes, road lines, building lines etc).
I was always taught to survey what I see, but only now do I understand the importance of this and how physically impossible that is as a human with limited work hours. Fortunately, Lidar does exactly this; it picks up millions of points and every point has an XYZ coordinate as well as a level recorded. So not only are you given an accurate 3D model, but you also have millions upon millions of points for you to use at any point in the design and build phase.
Wow! Now try to tell me you are not impressed!
Now you can also create a point cloud using photos as well this is called photogrammetry, which is where the points are picked up by taking photos from different angles and then processing this information into a point cloud. Most people generally think of UAVs when you say photogrammetry.
Both UAV and mobile mapping systems have their advantages, but the main advantages you have with using a mobile mapping system over a UAV is firstly you don’t need flight clearance or to jump through hoops for health and safety, and secondly, you can achieve higher precision, because you are usually nearer to what you are surveying with a mobile mapping system (usually within 50m of the subject, whereas with a UAV in the UK, usually, you must have at least 50m clearance from any potential unknowing member of the public.).
Scanners that use both of these technologies together make, in my opinion, a better, more accurate solution.
Now, where does the Mobile bit come into all this?
Most of these scanners are mounted on a tripod and must be sat still for anywhere between 1-5 minutes per scan (depending on the hardware). Then, once they have captured an area you need to move the scanner every 50 meters or so. It can be a slow process and can also be made more difficult if access is an issue or there are any obstructions.
Lucky for us Mobile Mapping has pushed both Lidar and photogrammetry into a system that can be worn or mounted on a vehicle and doesn’t need to be stationary for the scans!
So, not only is it incredibly efficient, but the time it takes to do the scans is substantially faster.
Now you may be thinking, as I was, ah yes but the accuracy must be poor or of lesser quality?
Nope. Most of these systems integrate IMU sensors to detect motion and use that information to improve results.
Mobile mapping opens up a world of opportunities for not only scanning inside and outside of buildings but at a speed and level of accuracy that means you can map huge construction projects in no time at all.
This is just the start, once you have the models, the exciting part is what you can do with it all!
More on that to come…