Lowest possible mapping altitude

Hello all,

I have received an unusual mapping request and am wondering is anyone here might have experience with a similar project.

The job is to map aggregate stockpiles for inventory estimates at an asphalt plant. The site is dead flat (other than stockpiles) but is located within controlled airspace with a max LAANC altitude of 50 ft. Yikes! I have not reconnoitered the site yet but am told that the stockpiles may approach that height. If so, then obviously, game over. However, if they are lower, say 30 feet, I wonder if any have had success attempting to map at this altitude/clearance and, if so, if they can provide any suggestions. GPC’s will be established prior to flight. Site is only about 4 acres so high overlap and slow speed is feasible.

If I have sufficient clearance for the flight I was thinking maybe a cross grid with overlap of 75%. If this makes sense at all, would gimbal be best at nadir or maybe an angle, say 65 degrees?

Any input appreciated.

Steve

With that small of an elevation difference between the tops of the piles and the flight altitude you will have to run an oblique angle mission and I think the crosshatch is the right idea. Even with that you are going to need to turn your overlaps up to max or you will not get enough matches on the tops of the piles. Or you might consider running two missions with at least 60/60 overlaps, but the second mission direction would be 45 degrees to the first. Also, raising the gimbal pitch a little will help with overlaps. Without seeing the site it’s hard to be certain.

In my opinion if you are just going after stockpile quantities then GCP’s are a waste of time. Stockpiles are small local areas of A minus B so the error in that small of an area is negligible.

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Thanks Michael. Great input as always. If I get the project I will report back results. When you say two missions, do you mean that each mission would be a crosshatch mission (so four passes altogether)? Both missions with gimbal at 65 degrees? With that many passes, I should certainly have enough data.

Thanks again

Steve

My pleasure. Yes, two crosshatches. One North-South-East-West and the other 45 degrees to that. You might only need 70/70 overlaps, but it will ensure that you get all “sides” of the piles. Like I said before the tops of the piles will be the key. I have flights that if I go below 200ft above the highest objects you can actually see the affects in the accuracy report coverage map. Another thing this will help with if there are any crushers or screeners.

Thanks again Michael. Hope I will get the chance to fly it. Again, I will report back on lessoned learned if I do.

Steve

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