Power line interference and other questions

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I recently purchased a Phantom 4 mostly just to fly around on
Some property I own. There is a high power transmission line that runs across the property. Are there any issues to be concerned about other than collision? I would like to fly over the lines to reach the far side and f my property, but am a bit concerned with getting a lost signal.
Also the property is quite steep. Will the obstacle avoidance sense the hillside and avoid colliding with it?
Altitude: Is the altitude readout from the ground under the done, or from sea level?
 
Altitude: Is the altitude readout from the ground under the done, or from sea level?
H is the height above the level of the launch point
VPS is the height above ground (but it only works as far as 10 metres)

i-tWD8pRk-M.jpg
 
As I understand it H is height above ground using GPS referenced to home or launch point, and VPS is height above ground using VPS cameras referenced to ground or any object within 10 meters beneath drone.
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As I understand it H is height above ground using GPS referenced to home or launch point
H is not height above the ground at all.
It's elevation above launch point.
It comes from the barometric sensor in the IMU.
GPS is not involved at all in altitude for flight purposes.
 
H is not height above the ground at all.
It's elevation above launch point.
It comes from the barometric sensor in the IMU.
GPS is not involved at all in altitude for flight purposes.

Dumb question but does H go to a negative number if you launch from a high point and go down?
 
H is not height above the ground at all.
It's elevation above launch point.
It comes from the barometric sensor in the IMU.
GPS is not involved at all in altitude for flight purposes.

Ok, so I understand that GPS is not involved in altitude for flight as it is the barometer Barometric Pressure Sensor Keeps Drones Stable | Sensors Magazine but I get confused on the “height above ground and elevation above launch point.” What is the difference between the two, and is the height derived from the barometer AGL or MSL?
 
I recently purchased a Phantom 4 mostly just to fly around on
Some property I own. There is a high power transmission line that runs across the property. Are there any issues to be concerned about other than collision? I would like to fly over the lines to reach the far side and f my property, but am a bit concerned with getting a lost signal.
Also the property is quite steep. Will the obstacle avoidance sense the hillside and avoid colliding with it?
Altitude: Is the altitude readout from the ground under the done, or from sea level?

I don’t know this from experience but I have read that power transmission lines can interfere with signals from the controller.
 
I have not experienced any lost signals flying to the other side of high power transmission lines but I fly well above them when I cross. Obstacle avoidance will sense the hillside but speed plays a factor in stopping in time to avoid a collision. Maybe someone with experience flying toward a gradual slope will pitch in with an answer.

You know about MSL (Mean Sea Level) and AGL (Above Ground Level). Think of it like this. Assume you are private pilot flying out of an airport that sits at 1000' MSL. Normally your altimeter will say 1000' when you use the airport's current barometric pressure to set it but this time you decide to ignore the barometric pressure. You simply set our altimeter to zero and take-off. You climb until your altimeter reads 3000' then set a course for an airport near the ocean. It sits at 100' MSL As you fly toward your destination you have no clue what our MSL is because you did not set your altimeter with the barometric pressure. It gave you AGL ONLY When flying over the top of your departure airport. The AGL value constantly changes as the ground below you raises and lowers. This is the way it is with drones. They just set their altimeters to ZERO (0) and take off.
 
Ok, so I understand that GPS is not involved in altitude for flight as it is the barometer Barometric Pressure Sensor Keeps Drones Stable | Sensors Magazine but I get confused on the “height above ground and elevation above launch point.” What is the difference between the two, and is the height derived from the barometer AGL or MSL?
Look at the screenshot again:
i-tWD8pRk-L.jpg

The drone was launched from close to the drone flyer on the rocks.
It is 5.5 metres higher than the point it was launched from. H=5.5m
But the rocks drop away toward the sea and are 9.4m below the drone.
The sea is a few metres lower than that.

Your barometer doesn't bother with AGL or MSL.
It doesn't know what sea level is or how far the ground is below the drone.
Wherever you start the drone is zero, whether it's on the edge of the sea or on top of the Rockies.
 
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There is a high power transmission line that runs across the property. Are there any issues to be concerned about other than collision? I would like to fly over the lines to reach the far side and f my property, but am a bit concerned with getting a lost signal.
Loss of signal won't be an issue.
The cables have a magnetic field that varies in strength with the current the wires are carrying.
The magnetic field could affect your compass if your drone gets close enough.
How close is too close? It's not easy to say.
Low voltage lines have a small magnetic field and aren't much problem.
Bigger cables = bigger field.
At this distance with this cable, there is no detectable effect:
i-fCm7SWD-L.png

Somewhere closer, there would be, but I didn't go closer to find out where.
Also the property is quite steep. Will the obstacle avoidance sense the hillside and avoid colliding with it?
Obstacle avoidance is good but it isn't magic.
It has a number of limitations and can bee fooled by things like poor lighting or small twigs.
The manual has a list of conditions that the OA system can have trouble with.
 
Where I fly, I follow transmission lines just like in the picture above (double towers with many lines). I follow them at 50' higher than the tower top, and have never experienced an issue with telemetry interference.
 
Look at the screenshot again:
i-tWD8pRk-L.jpg

The drone was launched from close to the drone flyer on the rocks.
It is 5.5 metres higher than the point it was launched from. H=5.5m
But the rocks drop away toward the sea and are 9.4m below the drone.
The sea is a few metres lower than that.

Your barometer doesn't bother with AGL or MSL.
It doesn't know what sea level is or how far the ground is below the drone.
Wherever you start the drone is zero, whether it's on the edge of the sea or on top of the Rockies.

That makes sense, thanks for the explanation.
 
I have flown P4A and P3A over and under high lines. Big transmission lines. Don’t dilly dally, get on through them.
I did notice that preflight gave me some compass errors and I had to move away about 20’ further. I was flying a fire scene on the highline ROW. Didn’t have any interference in flight and flew approx 1/8 mi past them.

Recommend you find a safe spot to launch without interference. Hover for a few minutes above head height then above highline height. Watch for interference. If flying under, set RTH accordingly.
 
There is a 14,400 volt line just north of my property. I first elevated to 400 feet to fly over it the first with no problems. Later I was on a Litchi waypoint Mission across these lines and towers when my old Phantom 4 lost video link so I I started RTH. I didn’t realize I had the altitude set to 30 meters and the drone flew right towards the high voltage lines! When I watched the video I saw that it just cleared the lines. I didn’t notice any interference from th power lines.

Thanks
Jim
WA5TEF
 
I have a 138kv line crossing the rear of my property. I've flown about 10' above the highest wire which is the ground wire using my P4P. No problem at all. I also followed the power line about one mile to my buddies house and he does the same with his P3S. We stay over the right of way so were not over any houses or vehicles. That being said I do avoid cellular towers or microwave towers.
 
I have a small wireless internet business I run from my 110 foot ham radio tower. It has 3 sector antennas on 2.4 Ghz and one dish antenna on 5.8 Ghz. I frequently fly my Phantom 4 Pro V 2.0 and previously my Phantom 4 up to inspect the antennas and tower. I have flown right in front of the directional antennas with no problems at all. DJI's frequency hopping system seems to be immune to this type of interference. Great system, if only they had a decent customer service department!

Thanks,
Jim
WA5TEF
 

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