Generally Stupid Questions

[The Real DrSudz]

I believe I saw a discussion that leads me to believe the drone's flying height, i.e. max and rth are determined by the rth point vs the actual height of the drone at any point. Is that correct. Does that mean for example that I need to estimate the height of trees on a hill I may be flying over relative to the takeoff point?

 

[dawgpilot]

I believe I saw a discussion that leads me to believe the drone's flying height, i.e. max and rth are determined by the rth point vs the actual height of the drone at any point. Is that correct. Does that mean for example that I need to estimate the height of trees on a hill I may be flying over relative to the takeoff point?

Yes, everything is set in reference to the take-off point. So you need to take into account any sloping terrain you might be flying over.

 

[The Real DrSudz]

Thank you dawg!

 

[phantomi]

I lost a drone precisely for this. I was flying and go around a building not taller then my rth height, but unfortunately it were in a hill. After disconnection the drone ascend but it can't surpass the building...

 

[THE CYBORG]

The Real DrSudz The only stupid question is the one you don’t ask

 

[Wild Wayne]

Does that mean for example that I need to estimate the height of trees on a hill I may be flying over relative to the takeoff point?

Yes. You can change your RTH altitude while the drone is in flight.

 

[NLOL]

Wow! That seems to me, in hilly country, that one might easily break the 400' AGL ceiling. To get back to the launch point - guaranteed if I fly to the top of a hill more than 400' higher than my launch point. Oh, gees - if I fly to a higher point on the other side of a valley an expereince a RTH event ...

Question - fail safe return to home mode - If I have this right the drone backtracks its out bound path. Does that include altitude or just lat and long?

 

[lee82gx]

Wow! That seems to me, in hilly country, that one might easily break the 400' AGL ceiling. To get back to the launch point - guaranteed if I fly to the top of a hill more than 400' higher than my launch point. Oh, gees - if I fly to a higher point on the other side of a valley an expereince a RTH event ...

Question - fail safe return to home mode - If I have this right the drone backtracks its out bound path. Does that include altitude or just lat and long?

Generally just lat and long. It first ascends to rth height if lower than current height or keeps to the existing height. I believe if apas is switched on it MAY ascend or descend to avoid obstacle during rth but in practice this behaviour is very rarely seen, especially in air 1. More than likely it will navigate around the obstacle at the rth height.

 

[Olav van Gerven]

One thing I do to check if my RTH (or any mission level!) is okay to a new area I fly is, to just make a straight lift-off to the altitude I want to set or have set. Then, with the camera horzontal, I make a slow 360. If I have free sight, I am relatively sure that my altitude is okay. If I see something above my horizon, I keep it in the camera and rise further, untill I either have it under my horizon or reach my mac. flight altitude for the area. It only takes a few minutes from the first battery but it avoids problems.

 

[Dave Maine]

This problem applies to waypoint missions as well. All altitude references are from the altitude of the takeoff point. The pilot must always think about this. You can easily fly into buildings, trees, slopes and have the drone altimeter showing hundreds of feet of altitude. I have some terrifying footage of my drone flying under some telephone wires between 2 branches 25 feet below the tree tops on a Litchi mission.

The pucker factor was very high.

 

[NLOL]

Thanks guys. I see I have many challenges ahead. New to drones - have an MA2 due soon. I'll be flying in very remote, far north, and very steep areas above and below tree line, mostly for preliminary geologic views and land route planning. I've been thinking pre-programmed routes would be heavily relied on. Now it appears I need to be careful to keep visual contact, radio contact, and satellite views always present, and closely consider/plan enabling/disabling RTH on particular flights - for instance flying into a situation (for instance, a narrow gorge I have a good view into), or inspecting a coulie, will be less program-and-go than I hoped. That raises the question: is a fail safe return based on GPS track, inertial track, or programmed (GPS) route?

 

[NLOL]

Dave, you posted while I was writing previous post. I'd been wondering how altitude as handled. Seemed like cartography, GPS, and distance measuring sensors, wouldn't work well. So, drone altitude readouts always reference +/- from launch point altitude. I think, hmmm, I think that will indeed sometimes be a challenge; I'm guessing the altitude sensor is barometric pressure based - have to make correct for that when using topos. Do the aircraft systems/apps report barometric altitude at launch point, or is that only/always reported as 'zero'?

 

[Dbez1]

Launch point is zero. To answer a question earlier in this post...if you launch from a valley that is 300’ deep and fly to the top of the hill, you can legally set your RTH at 700’, more if there are buildings at the top of the hill. Just don’t forget the VLOS thing.

 

[butterflyslicer]

This problem applies to waypoint missions as well. All altitude references are from the altitude of the takeoff point. The pilot must always think about this. You can easily fly into buildings, trees, slopes and have the drone altimeter showing hundreds of feet of altitude. I have some terrifying footage of my drone flying under some telephone wires between 2 branches 25 feet below the tree tops on a Litchi mission.

The pucker factor was very high.

Maximise your altitude to avoid obstacles .

 

[Dbez1]

The only problem with “maximizing your altitude” is that the higher you go, the more wind there is. That is a consideration for those of us with MM. Probably not quite as important for MA2 pilots.

 

[Dave Maine]

The launch point barometric pressure is saved on launch, and does not change during the flight. All "heights" are offsets from this number. Atmospheric changes will cause this offset to be less accurate.

RTH, retracing or following routes are based on the stored GPS locations in the drone. Without adequate satellite coverage, none of these will work. As the drone flies, the GPS location is fused with the inertial guidance information to create new course information, and measure progress along this piece of the flight feeding corrections back to the combined GPS/Inertial solution.

Without functioning GPS real time position information, all the inertial guidance information will do is attempt to maintain 3-dimensional stability. Winds, updrafts and other perturbations will not be sensed or acted upon. Flight will be only controlled by the images on the tablet, and modified sometimes by the optical sensors.

Another thought is got understand your Latitude of interest. GPS coverage is far poorer at high latitudes, and may not be reliable where you are trying to map.Flying in canyons or where the 180 degree view of the sky is compromised will make this problem worse.

You have an interesting problem to solve. Keep us posted.

 

[butterflyslicer]

The only problem with “maximizing your altitude” is that the higher you go, the more wind there is. That is a consideration for those of us with MM. Probably not quite as important for MA2 pilots.

True (also a mini pilot) but then you lower your altitude and fly like a butterfly.

 

[NLOL]

Dbez1 - Let's assume your example (no trees/building) and the RTH max altitude is set at 700' - do I understand correctly that I nevertheless, still have a controlled/piloted outbound flight restriction of 400' AGL, and the same controlled/piloted return to launch point restriction of 400' AGL? However, if the return to launch point is either system or pilot initiated RTH flight, that 700' AGL is allowed? In other words, the aircraft would, upon RTH initiation, rise to 700', fly to point above launch site then descend to launch point - all perfectly with regulations?

 

[butterflyslicer]

 

[dawgpilot]

Dbez1 - Let's assume your example (no trees/building) and the RTH max altitude is set at 700' - do I understand correctly that I nevertheless, still have a controlled/piloted outbound flight restriction of 400' AGL, and the same controlled/piloted return to launch point restriction of 400' AGL? However, if the return to launch point is either system or pilot initiated RTH flight, that 700' AGL is allowed? In other words, the aircraft would, upon RTH initiation, rise to 700', fly to point above launch site then descend to launch point - all perfectly with regulations?

No, the 400 foot AGL limit is a hard legal limit. There is no loophole that allows you to go above 400 AGL simply because your drone initiated some kind of RTH mode. You need to set your RTH heights to be appropriate for the terrain you will be flying over so that you don't exceed 400 feet AGL.