Monitoring slopes on highways

[Dragoons]

Hello guys,
I'm a new member of this forum so my apologies if this topic doesn't fall under this category.

The problem I ran into is:
My company recently acquired a contract for monitoring slopes on a highway. There will be around 150 slopes varying from 10-150m in height.
The gathered measurements will be used by geologists to monitor cracks in the rock faces for mending of the rock faces so they dont fall down on the road. It is a 5 year contract so the sites will be remonitored each year once atleast and I'll need to compare the multiple data sets.

Since I'm new to the laser scanning department could I please get your oppinions on:
-What type of laser scanner to use (phase or pulse; type and model etc.)
-Would this task be possible with a UAV mounted laser system (if so could you point me in a direction on which ones to look at)
-And finally which software suite would you recommend for this task? I've been looking over the net but I haven't really found a program which would have automatic detection of cracks; since there are many sites I'd rather not do this by hand but somehow automatize the whole process.

Thanks in advance!

[Diamond Digger]

Dobar Dan Dragomir
Firstly few questions regarding your project:
1. What is the total length of the highway to be monitored?
2. What is the approx. square area of all slopes/ rock faces to be monitored?
3. Do you need to monitor other slope conditions i.e. change in shape, spillage in addition to rock face fractures?

Secondly regarding the hardware. Even the top-notch mobile mapping system (either terrestrial or UAV based) will not be able to reveal cracks narrower than few centimeters. They will simply fall between the points in your point cloud. Or you need to get extremely dense point cloud for each slope from a static scanner. Here we come to the question 1 above - how much time it will take to survey the entire highway by 'stop-and-go' approach?
Still your cracks can fall between the cracks (sorry for the punt). I think you need a high-resolution digital camera to complement your mobile mapping system and drape the photographs over slopes DEM.

To compound the issue I am not aware of any software which has build-in automatic crack extraction algorithm. We tried that in our shaft inspection software but then backed away as it is very difficult to mathematically describe a crack as an object (unless you have a gaping hole) never mind to distinguish it from a shade or any other change in lighting conditions. Perhaps a solution could be to have a person looking simultaneously at two subsequent high-resolution DEM/images of the same rock face - may be in 'fly-through' mode - where software only highlights the changes but this person decides whether it is a crack or not. In any case it could be an interesting project to take part in. If you want to discuss it in more details please write to my email [email protected].
Kind regards
Sergey

[Formula1982]

I think to give you an answer on software, we need to know the hardware you're going to use, and how.
And to know the best options for hardware, we need to know how large each area is, what the minimum size of 'crack' you need to identify is, and how much time you have budgeted per area.

[johnhalifax]

Hi Dragomir,

We have been monitoring ground movement for well over a decade now. We now use a Riegl VZ1000 which has a calibrated Nikon D700 camera. We use Riscan Pro to undertake surface comparisons. Using this method we can identify movement in excess of 20mm. For cracks less than this we use the images, providing the cracks are visible.

I have a couple of power point presentations one for ground movement and one for structural monitoring I can make these available via a link. Please contact me direct at [email protected] this goes for anyone else who's interested.

I wouldn't consider a scanner on a UAV, too expensive especially when they crash and you wouldn't get the accuracy. I would consider a UAV with a DSLR camera, again you wont be able to measure very small movement but using ortho rectified images you will see if more cracks are appearing or lengthening.