Questions about 3D laserscanning

jo · Newbie Joined: Jun 15, 2008 Posts: 1

Hey,

I have some questions about 3D laser scanning. I've searched on the internet, but is defficult to find information about it:
question 1) What's the difference in accuracy and range of laser scanning devices: time-of-flight and phase-based
2) Can i scan snow, water using a laser scanning? how does this type of surface affect the laser scanner?
3) are there any problems using the scanner when scanning in the dark or scanning in light invernoments?

I hope I can find my answers here
thanks

Jonathan

NJD1995 · Newbie Joined: Jul 07, 2008 Posts: 1

I have been scanning for an engineering firm for 3 years. Time of flight scanners give you longer range with longer scanning times. We have a Leica and it is around 4000 pts per second. Manufacturers all have different specs but for the most part around 300m, but I will never do that. Takes too long and there is too much noise involved with the data. The phase based scanners are around 5000,000 per second but only have a range of around 30m. I was stuck in a snow squall and the scanner will scan snow. It wound up looking like a firework. We have scanned water just b/c it fell within our scan, and it wont pick it up. We work in a lot of train and subway tunnels and it will scan in the dark. The problem you encounter is making sure you and your crew can see the targets in the dark and you frame out what you actually want to scan. Some things to think about, dark surface, black, dark red, dont scan real well, and neither does some type of flashing or trim. Most salesman will give you a demo. I dont know what part of the country you are in, but we did a real world demo in NYC. We own 2 a Leica and a Trimble. Since we took delivery of our Leica ScanStation, our Trimble has sat in the case in our equipment room. Hope some of this helped.

rob · Newbie Joined: Aug 18, 2008 Posts: 1

I'll add some feedback too:
yes the scanner will scan snow and water. I've picked up snow, blowing and falling and rain in scans. As for ground cover we pick up really good returns from snow! Water yep we can get water too, as mentioned earlier water can be tricky. The higher the angle of incidence the better return you get from water. A low angle of incedence can actually produce a reflection below the surface. One time I was scanning an area that had an asphalt parking lot and got reflections below the parking lot, it was kind of cool once we figured out what it was.
Scanning in the dark works really well, the only problem is finding the targets in a dark photo, but that has a work around too.