One of our engineering clients contacted us for a potential project but I’m unsure if using LiDAR is a good option for their needs.
Their client is developing large windmills so they need to transport large/heavy parts using heavy transport vehicles through public roads. They want to monitor the road condition before and after and want to see if there are any vertical shifts in the manholes. Their minimum vertical accuracy is 0.1feet (or better).
My question is, will using LiDAR be a good option for monitoring the vertical shift in the manhole over a 13-mi road stretch? Any suggestions on flight/mission parameters, etc?
Here are my thoughts (I was civil engineer consultant for 15+ years):
I would set up and hand level in each manhole, bringing your shots/datum back to known good points (established survey monuments).
This is the only way to accurately describe, over time, the movement of the manholes. Nothing may happen to them, or they could move. Hand leveling/bringing survey elevation control, from known monuments, that the legal people can easily see and decipher is your best bet… especially if the municipality wants to make their life harder than it needs to be.
I would take a shot in the middle of the frame/cover, and 4 additional shots 6" or 150mm around the manhole on the compass points… these will help describe any settlement of the road surface/base material construction around the manhole.
Lidar is awesome, but you won’t get the data you need. Everytime you survey with lidar, the GNSS signal is slightly different and corrected differently each day. (That is why I will never lay out gravity pipe with a GPS).
It would be a pain to get all that data lined up to provide useful measurements over time.