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Maximum altitude below cell tower height

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I’m working on a survey which is in a 100 foot box near my airport. It looks like there may be a cell tower higher than the 100 foot altitude in the area I need to survey. I’m wondering what to do?
My gut feeling is to fly the mission and if the throne appears as though it will intersect with the cell tower I can abort the flight.
Chances are that it will not intersect anyway. Is that a reasonable thing to do? Has anybody ever done that?
 
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I’m working on a survey which is in a 100 foot box near my airport. It looks like there may be a cell tower higher than the 100 foot altitude in the area I need to survey. I’m wondering what to do?
My gut feeling is to fly the mission and if the throne appears as though it will intersect with the cell tower I can abort the flight.
Chances are that it will not intersect anyway. Is that a reasonable thing to do? Has anybody ever done that?
Some more details would be helpful. Are you doing this survey as an automated mapping mission, or are you flying manually? If flying manually then you have no issues. If automated then I would be very careful since judging depth on the device screen is a bit difficult., and you may not have time to abort if the automated sequence is flying into the tower.

Of course you need to apply for LAANC authorization before flying so if it were me, I would get the exact height of the tower in feet AGL. Then I would add 25 feet as a margin of error and apply for that height when requesting authorization. Explaining the situation and limiting your flight grid to the immediate vicinity of the tower may get you the increased authorization.
 
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This is an automated flight. As per flight rules I’m eyes on the drone and not the screen

LAANC done already.


Not sure about the reference to increased authorization by limiting the flight grid.
 
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I’m working on a survey which is in a 100 foot box near my airport.
What is a 100' box? Do you mean 10,000 sq. ft? That seems like an awfully small swath of land (.22 acres). Can you clarify?



It looks like there may be a cell tower higher than the 100 foot altitude in the area I need to survey. I’m wondering what to do?
Fly 150'. Why are you flying so low? 100' AGL is a GSD of < 1/2". Standard GSD for mapping is 1". My entire mapping career I have never flown under 150' AGL, and RARELY fly under 250' AGL.



My gut feeling is to fly the mission and if the throne appears as though it will intersect with the cell tower I can abort the flight.
It would be prudent to fly 200' AGL, as this will insure you clear all utility towers.



Chances are that it will not intersect anyway. Is that a reasonable thing to do?
Not reasonable. You can always fly up to the tower manually to learn the tower's altitude. Remember to launch your drone from your mapping launch site to account for any elevation changes that may exist between the tower's base and your launch site. The tower may only be 100', but if it's base is 15' above your launch site, that's a total AGL of 115'. I was almost bit by that bug ONCE.


Has anybody ever done that?
No. Don't risk it. Fly higher. 100' is ridiculously low for mapping.

D
 
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I think I may not have been adequately clear in my original post. The 100 foot box is the maximum altitude in a section of class D airspace where I am flying. Not legal to fly higher.

The area I’m mapping is fairly small. About a 15 minute flight at 100 feet AGL.

Tower obstruction penetrating the 100 foot ceiling. The chances are fairly high that my flight path will not intersect to the tower. So, my thought is to fly the mission autonomously while keeping a keen eye on the bird and prepared to abort the mission if it appears that the bird will intersect with the tower. It’s highly probable that the drone will fly on each side of the tower anyway.

If an intersection with the tower appears imminent, then I will abort, land and then reset the mission to fly 90° opposed and then retry.
 
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I think I may not have been adequately clear in my original post. The 100 foot box is the maximum altitude in a section of class D airspace where I am flying. Not legal to fly higher.

The area I’m mapping is fairly small. About a 15 minute flight at 100 feet AGL.

Tower obstruction penetrating the 100 foot ceiling. The chances are fairly high that my flight path will not intersect to the tower. So, my thought is to fly the mission autonomously while keeping a keen eye on the bird and prepared to abort the mission if it appears that the bird will intersect with the tower. It’s highly probable that the drone will fly on each side of the tower anyway.

If an intersection with the tower appears imminent, then I will abort, land and then reset the mission to fly 90° opposed and then retry.
2 things:

1) 100' AGL includes all mountains, hills, buildings, structures, poles, trees and towers. In other words, you're allowed to fly 100' OVER and ABOVE these objects within a 400' radius of these objects. Around here, elevation is fairly dynamic. So unless you're flying over a wheat field in Kansas, you probably have some wiggle room on your actual elevation.

2) If you're concerned, again, you can fly manually up to the tower and let your drone's telemetry give you actual height of the tower. I have used this method many times to ascertain the actual height of a tower or building. While this method is not 100% accurate, it will get you well within the ballpark.

D
 
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100' AGL includes all mountains, hills, buildings, structures, poles, trees and towers. In other words, you're allowed to fly 100' OVER and ABOVE these objects within a 400' radius of these objects.
This is NOT true for authorization in controlled airspace, which is what the OP is trying to accomplish. If authorization is obtained for 100 feet AGL, that is absolute. The drone can at no time exceed 400 feet above the ground directly vertically below it.
 
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2 things:

1) 100' AGL includes all mountains, hills, buildings, structures, poles, trees and towers. In other words, you're allowed to fly 100' OVER and ABOVE these objects within a 400' radius of these objects. Around here, elevation is fairly dynamic. So unless you're flying over a wheat field in Kansas, you probably have some wiggle room on your actual elevation.

2) If you're concerned, again, you can fly manually up to the tower and let your drone's telemetry give you actual height of the tower. I have used this method many times to ascertain the actual height of a tower or building. While this method is not 100% accurate, it will get you well within the ballpark.

D
Not sure I am in agreement with statement #1.... I'm pretty sure that in controlled airspace requiring a waiver, that the altitude limits set by the FAA are based on factors of manned flight paths. Going above the ceiling limit set forth by the LAANC system would be a violation. I did extensive research on how these altitude limits were determined. The FAA is aware that terrain can change quickly in some areas and there are working on the possibility of creating smaller segments for these areas. The 400 ft above within a 400 ft radius may be for NON class B, C, or D space. I'll double check om that.... Think of it this way... you in a 100 ft max altitude AGL area say 3/4 mile from the approach end of a class D airport. You got you waiver so your good... There is a tower at 150 ft AGL in the vicinity. Your saying that you could fly at 500 ft AGL within a 400 ft radius of the tower.... I don't think so. I may be incorrect, but my studies indicate that the max altitudes on those LAANC charts are absolute.

Regarding point #2, I do that when necessary, but irrelevant here due to class D limit...
 
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This is NOT true for authorization in controlled airspace, which is what the OP is trying to accomplish. If authorization is obtained for 100 feet AGL, that is absolute. The drone can at no time exceed 400 feet above the ground directly vertically below it.
You got in just before me...


Also, the altitudes set in controlled airspace have already taken trees and structures into account. I can prove this by referencing:
JO_7200.23A_Unmanned_Aircraft_Systems_(UAS)
 
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This is NOT true for authorization in controlled airspace, which is what the OP is trying to accomplish. If authorization is obtained for 100 feet AGL, that is absolute. The drone can at no time exceed 400 feet above the ground directly vertically below it.
Okay...the OP was talking about 100' AGL. If he flies (gets authorization for) 250' AGL, he should clear every obstacle without a problem, AND remain compliant to the FAA rules. Agreed?

D
 
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Okay...the OP was talking about 100' AGL. If he flies (gets authorization for) 250' AGL, he should clear every obstacle without a problem, AND remain compliant to the FAA rules. Agreed?

D
And that should still be possible to do, just not with LAANC, correct?
 
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You got in just before me...


Also, the altitudes set in controlled airspace have already taken trees and structures into account. I can prove this by referencing:
JO_7200.23A_Unmanned_Aircraft_Systems_(UAS)
No need to prove it. I concede. I had forgotten that the rules are a little different inside controlled air space. My bad.

D
 
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And that should still be possible to do, just not with LAANC, correct?
It depends. You can apply for authorization at a higher than max grid altitude but there is no guarantee that it will be authorized. If you make a solid case in the comments and don't ask for too much, you may get it.
 
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I think I may not have been adequately clear in my original post. The 100 foot box is the maximum altitude in a section of class D airspace where I am flying. Not legal to fly higher.

The area I’m mapping is fairly small. About a 15 minute flight at 100 feet AGL.

Tower obstruction penetrating the 100 foot ceiling. The chances are fairly high that my flight path will not intersect to the tower. So, my thought is to fly the mission autonomously while keeping a keen eye on the bird and prepared to abort the mission if it appears that the bird will intersect with the tower. It’s highly probable that the drone will fly on each side of the tower anyway.

If an intersection with the tower appears imminent, then I will abort, land and then reset the mission to fly 90° opposed and then retry.
I've done something similar with my Inspire. I created two flight plans that excluded a 25 X 50 foot box around the tower on both plans. When you put them together it creates a 50 X 50 foot exclusion zone around the cell tower. Not elegant but it got the job done. Make sure you don't end the flight on one of the corners of the box. I was using Pix4D Capture to control the flight as well.
 

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