“Scanning is easy!” — How many times have you heard this sentence when presented with scanning technology? Well, let me give you a glance at a typical survey day. I bet the myth will be dispelled by the end of this post.
First of all, what is a static laser scanner — and what can it do? “It is an instrument that accurately measures the building and its surroundings,” is what I answer to any curious person passing by while scanning.
The proper, but still short, answer is “it is a machine that shoots pulsed laser light around. By measuring the returning time of the laser light, this instrument is able to determine the distance of each reached point and reproduce it in a 3D representation. A point cloud.”
How to overcome this problem?
1) critical thinking and communication with the client: what needs to be scanned? What information can be acquired by the scanner and what should be registered by means of different instruments (drone, total station, hand measurements…)?
2) Figure out the correct and necessary positions to capture every important feature of the site and reference targets (I’ll explain later). Moving the scanner from one point to another is not enough! We really have to check what is visible from each position and also adjust the height of the scanner accordingly.
On the job
A good job on site doesn’t just translate into acquiring correct and useful data, but also into a much easier processing phase. In fact, scanning is just the first part of the process: once the scans are performed, they must be processed and linked together in one single point cloud.
Scans can be linked together by means of overlap — the bigger the overlap, the easier the linking — or by the use of reference targets. In order to be effective, these targets need to be positioned in strategic locations and, most importantly, they cannot be moved! Now, this is funny: the 3D targets we use (white spheres with a diameter of about 15cm) are incredibly attractive to people and… animals!
A scanning physique
Other than defending targets, performing a survey is also about facing a great number of other challenges, both for the body and mind. So what is the “physique du role”, the necessary characteristics that a surveyor should have?
Be strong: Scanners might not be that heavy — about 5kg plus 2kg for the tripod —, but carrying them around the whole day over staircases and climbing on scaffoldings… Believe me when I say it is never easy to get out of bed in the morning after a scanning day. And don’t get me started with the strength necessary to set up the 5m high tripod! A job for titans!
Be brave: Acrophobia, claustrophobia, arachnophobia… If you suffer from any of the above, surveying might not be suited for you. Climbing scaffoldings and rooftops as well as crawling into tunnels and narrow passages between all kinds of dirt is our “pain quotidien”. I remember when, during a survey workshop in the first year of architecture school, a professor of mine said “if you can’t stand spending the day surrounded by pigeons guano and corpses, you should change faculty”. At the time I thought he was just exaggerating and being a drama king. I could not have been more wrong. Let’s be clear, I am sure somewhere in the world there are architects looking as the ones in the movies, being elegant and classy. But that’s just not my personal experience.
Be tiny: It is common knowledge that people in the past used to be a bit shorter than today, but sometimes, when entering particularly small attics and narrow passages, I really wonder if they were built by humans at all! Hi Smurfs and Lilliputian people, do you actually exist?
Be a team player: Do people with all these qualities combined exist? I doubt it. That’s why you need to rely on a team! At RealVisuals we rely on a multidisciplinary team of colleagues with different abilities, competencies and passions. As the art and history geek of the team, no doubt that, if I have the chance to hug a 13th-century column, touch an original wooden beam or look gothic statues in the eyes, I would crawl into any kind of dirt and climb the highest scaffolding!
I hope I managed to give you a more insightful picture of what scanning means. I do have only one last question for you: do you still think scanning is easy?
Alice | RealVisuals
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