I have rather large topo to perform in a gravel pit for a contractor, they have
approx. 5 million yards to excavate and haul @ $15 per yard. The area is a
rather large hill approx. 2200' long by 1800' high that they are going to cut into,
the hill is at a very steep 0.50:1 slope to a 1:1 slope with a significant amount of rain washouts with lots of little mini knolls and stoops, (its not uniform), because
of the steepness and danger of the slope conventional topo is not feasible for safety
concerns. They are looking for a rather detailed original ground surface that can
use to compare against future topo's for quantity payouts, I have considered Ariel mapping however they are concerned that because of the slope Ariel mapping will not
be accurate or detailed enough for what they are requesting, I have looked into scanners but about 1200' max range I don't think it will cut it, I was looking into
Lidar mapping to see what that has to offer, has anybody had any experience using this
type of data collection ? what are the pros and cons..? anybody have any other ideas
on how to approach this...? I can understand the contractors concern, at 15 bucks per yard,.. missing yards in the original topo can add up significantly in dollar value.
thanks for any help you may all offer..
Why not set up a traverse around the pile and pepper it with reflectorless shots? Some of the EDM's will shoot up to 1000 M.
I'm definitely not suggesting you try to do anything other than produce an accurate as you can topo. You might want to explain to the contractor that all the detail might hurt his quantities, not help them.
Can you post a pic? 2200' long x 1800' high is quite a hunk of terra firma.
A $60m job means there should be plenty of $$ in it for you to train or hire guys to do it with ropes and harnesses.
How do they propose to get drill rigs up there to commence blasting?
Trimble TX5 Scanner. Done and done. Scan in it two days then scan as they go. More accurate than a TS and is fast for quantities.
Vertical accuracies from helicopter LIDAR is apparently quite good, and you can't beat the speed or the detail, or for that matter the cost. I would think on a job like you describe you would be surprised for how much less the LIDAR data can be had for compared to conventional survey methods, although it will of course vary depending on where you are located.
In my opinion you're best off acting as quality control by verifying or establishing the control for the LIDAR guys and doing random spot checks to confirm the results are within promised quality parameters.