I recently ran a post on the weather durability of the Leica ScanStation Px line (P16, P30, P40) and really for all of Leica’s mapping products as the weather durability (IP rating) is phenomenal across the board. You can read my original post here, which includes a description of IP ratings. Following this post, I heard both directly and through the grapevine from several detractors of this piece to three main points:
- It wasn’t raining hard enough!
- Let’s see the raw data so we can see for ourselves!
- The data quality is questionable—the rain would cause refraction of the laser!
I’m here again to address these statements.
First off and as a small aside, if you look again at the photo I included (right), I used this shot because it captured the beautiful instance of a huge raindrop splash mid-splash in small pool of water on the top of the scanner. I love this shot…if only my big finger hadn’t found its way into the frame, as well! There is also a NIST-calibrated Leica Twin Target Pole that can be seen in the distance.
In response to the questions about our scanning in the rain:
1) Here is the video I captured on 05/23/2016 (excuse the mislabeled date on the video…my bad) of a torrential downpour and my scanning efforts to demonstrate these concepts:
I hope that we can all agree that it was raining hard enough in this scanning endeavor. It was pouring. I was soaked. The scanner was soaked. This was a good solid Midwest rain and thunderstorm!
If you’re interested in seeing the raw data from this scan, please contact me. I will be the first to tell you that there is more noise in this newer scan than there was in my original post. However:
- I was able to scan in a Midwest downpour.
- The noise level was very manageable compared to older generations of products in the Leica scanner family, other scanners on the market, and most notably, considering the volume of rain dumping on the scanner.
- I received sound measurement data. (See below for quality measurement information.)
Given that the original concerns were related to my first post, I would also be glad to provide the data from that scan as well upon request.
Above is the snapshot I included in the original post. The data is identical to the photo I published. I was amazed at the cleanliness, given this amount of rainfall. (Below is the video of the capture of the IL IAI data set, which demonstrates the rainfall.)
Finally, the third concern, which was presented to me on the Surveyor Connect board, was in regard to possible refraction of the laser.
SURVEYORCONNECT.COM Discussion (There are two pages, so please if you are going to read it, start at the beginning.)
In my most recent rainstorm scanning adventure, I scanned my NIST-calibrated Twin Target Pole (calibrated to a known of 1.000m) from 43+ meters and achieved 0.999m in my data return. I scanned the same target at 25+ meters and achieved 1.000m in my data return. From the greater distance, the .001m or 1mm variance can be attributed to any of the factors that affect terrestrial laser scanning upon which we base our (Leica’s Px scanning line) stated 3D positional error of 3mm-cubed at 50m and 6mm-cubed at 100m.
I also had published (on SurveyConnect.com) this response from a Leica engineer on the discussion of refraction caused by raindrops:
When we are scanning in the rain, essentially the Wave Form Digitizer is ‘flagging’ these points in the air as suspect due to the characteristics of the return laser signal. The Wave Form Digitizer is similar technology as multi-return sensing with aerial LiDAR mapping. When firing a laser up to 1,000,000 points per second, there is going to be points hitting rain as well as points actually getting through to their intended ‘target.’ I have run so many tests on this subject and compared to survey control, and it always is within acceptable tolerances that are universally accepted in the surveying community.
All-in-all, the data speaks for itself and I think our engineer’s points hold up solid.
As a final set of thoughts, two tips for your rainy day scanning endeavors:
- Use a remote controller to operate your scanner. Operating the user interface in the rain was difficult because of the amount of water on everything. So all things considered, the data rocks, but it became more difficult to fine-pick target points on the interface because of water cascading down the side. An iPad out of harm’s way (i.e., out of the rain) would have solved that problem, as well!
- When drying your support equipment (tripod, dolly, targets, etc.) be sure to dry it all off first upright, and then inverted, and then allow it to set and dry upright and then inverted. Water finds its way into all sorts of places on your equipment and properly dried equipment will reduce wear over time.
So there you have it! You now have more information to work with, including two raw, straight-from-the-scanner data sets featuring the Leica P40/PS40 scanning in the rain!
Please reach out to me if you are interested in the data download or have any questions. Until next time, keep on scanning!
For more information about laser scanning solutions for public safety, please contact us.