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Flying 101 Question - Over Hill and Dale
1097 23 2017-6-7
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jsantacroce
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Wondering what the normal steps would be where I take off from what would currently be my home location. And say I climb an obstacle or hill that is 200' high. My Vertical distance is now showing 200' and I have my max height set to 400'.

So I can change my max height to 600', but if it is a large object such as a small mountainous range or hill that sloops, and I want to stay 200' above the entire slooping hill (think bell curve) which would still be within the 400' FAA limit along the way. What is the best way to do this? Or is there something basic I am not aware of yet. I don't want to stop and reset the home point along the way.

Thanks!

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Geebax
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Unless you land, shut down the aircraft and re-start it, you will not be resetting the home altitiude anyway. But I don't understand the main point of your question being 'what is the best way to do this'.
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racer888
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Not quite sure I follow what you are asking but the FAA rule is 400 feet AGL, meaning you are allowed to fly 400 feet above what ever elevation you are standing on. You can also fly 400 feet above a structure if you are within 400 feet of it. So in theory if you were inspecting a tower or building you can be 400 feet above it.The home point will be recorded from where you take off from so if you are moving while you are flying you would need to reset the home point or the AC will return to the original home point, which may be ok but if you have moved considerably you would want to reset it.
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jsantacroce
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racer888 Posted at 2017-6-7 16:59
Not quite sure I follow what you are asking but the FAA rule is 400 feet AGL, meaning you are allowed to fly 400 feet above what ever elevation you are standing on. You can also fly 400 feet above a structure if you are within 400 feet of it. So in theory if you were inspecting a tower or building you can be 400 feet above it.The home point will be recorded from where you take off from so if you are moving while you are flying you would need to reset the home point or the AC will return to the original home point, which may be ok but if you have moved considerably you would want to reset it.

Yea, don't think I explained it clearly. I don't want to reset the home point because if something happens I would still like it to RTH where I started from. But I would like to know the AGL at all times and not just from the home point is probably the best way to state it. If my drone is 1000' away and over a hill or structure, is there any way to determine the height above that hill or structure at that time without resetting the Home Point.

Thanks
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DJI-Jamie
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jsantacroce@hvc Posted at 2017-6-7 17:01
Yea, don't think I explained it clearly. I don't want to reset the home point because if something happens I would still like it to RTH where I started from. But I would like to know the AGL at all times and not just from the home point is probably the best way to state it. If my drone is 1000' away and over a hill or structure, is there any way to determine the height above that hill or structure at that time without resetting the Home Point.

Thanks

If I'm understanding you correctly, I don't believe it's going to be possible without you researching the landscape and mentally adjusting accordingly.
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racer888
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jsantacroce@hvc Posted at 2017-6-7 17:01
Yea, don't think I explained it clearly. I don't want to reset the home point because if something happens I would still like it to RTH where I started from. But I would like to know the AGL at all times and not just from the home point is probably the best way to state it. If my drone is 1000' away and over a hill or structure, is there any way to determine the height above that hill or structure at that time without resetting the Home Point.

Thanks

Ok, now I see what you are asking. I do not believe there is a way to see that as it is my understanding the altitude is always above the home point.  I say this because i was shooting a real estate video for a lot the other day and the front of the lot drops off almost 800 to 1000 feet and when I flew out past the drop off to get the view my altitude was still reading 150 feet and if it was recording actual AGL it would have been at least 1000 or 1100 feet.
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Labroides
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jsantacroce@hvc Posted at 2017-6-7 17:01
Yea, don't think I explained it clearly. I don't want to reset the home point because if something happens I would still like it to RTH where I started from. But I would like to know the AGL at all times and not just from the home point is probably the best way to state it. If my drone is 1000' away and over a hill or structure, is there any way to determine the height above that hill or structure at that time without resetting the Home Point.

Thanks

Just like the pilot of a Cessna, you have to do the thinking because your aircraft has no way to know what's below it.
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jsantacroce
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Labroides Posted at 2017-6-7 17:56
Just like the pilot of a Cessna, you have to do the thinking because your aircraft has no way to know what's below it.

And I was hoping I was actually missing something. Too bad there isn't some type of (for lack of better term) ping going out to the ground level to tell the current distance above any object you are over besides distance above the home point. I would find that helpful.

Thanks all for the input.
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Labroides
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jsantacroce@hvc Posted at 2017-6-7 18:24
And I was hoping I was actually missing something. Too bad there isn't some type of (for lack of better term) ping going out to the ground level to tell the current distance above any object you are over besides distance above the home point. I would find that helpful.

Thanks all for the input.

This is one of the smallest and cheapest radar altimeters:  
https://buy.garmin.com/en-US/US/p/166298
It weighs 3.5 pounds and costs US$6300 for the sensor alone.

That's why most light aircraft don't have that ability either.
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Cetacean
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jsantacroce@hvc Posted at 2017-6-7 18:24
And I was hoping I was actually missing something. Too bad there isn't some type of (for lack of better term) ping going out to the ground level to tell the current distance above any object you are over besides distance above the home point. I would find that helpful.

Thanks all for the input.

Aloha santa,

     There is a work-around to it all.  As Labroides noted, you have to do all the thinking.  I live in a multilevel flying environment and have to use variations in altitude to stay legal.  I am also on the 5 mile line from a military airfield next to a 2000 foot line of cliffs called Pali.  In the other direction is the ocean.

     As racer noted, you are allowed to fly 400 feet by and above a "structure".  A mountain is considered a structure.  Now comes the adaptable part.  The Phantoms are able to fly as much as 500 meters above the Home Point.  That comes out to 1640 feet, or so.  I cannot summit the mountain cliffs behind my house, but I sure can climb a large portion of it and stay legal.

    One time, before I started flying the full 1640 feet, my friend and I tried some mountain math and used the Geebax trick above of shutting down and restarting to get another 150 or so feet.  It was a lot of fun (and the video is kind of funny), but it is much easier to just change the max altitude.

     You do not have to fly the full 500 meters, but you can use the leeway to set the max altitude more than 400 feet above the Home Point if you are flying near a structure.  In your case with the 200 foot rise or hill, you can set the max altitude to 600 feet.  That way if you are flying and start to go above 600 feet the remote controller girl will tell you that you have reached the max altitude and it will display on the screen.  If you want to go the full 400 feet above the hill, you can reset the max altitude to 800 feet (the setting is in meters so you have to do the math first).

     The other day, I was making a video of the super high tides we are getting to see how far they are encroaching these days.  (Sea level rise is getting more attention in the islands with global warming.)  Because I was less than 5 miles from the Marine Corps Base Hawaii Kaneohe Air Field, I had to fly below 150 feet.  So I set my max altitude to 140 feet (because if you fly above 150 feet they can make you lose control of your aircraft).  It turned out that I never really needed even the full 140 feet.  All the interesting stuff was way down on the shoreline.

     So, there are some tools that can help but as Labroides said, you have to do the math.  Hope this helps!

Aloha and Drone On!
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jsantacroce
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Cetacean Posted at 2017-6-7 19:50
Aloha santa,

     There is a work-around to it all.  As Labroides noted, you have to do all the thinking.  I live in a multilevel flying environment and have to use variations in altitude to stay legal.  I am also on the 5 mile line from a military airfield next to a 2000 foot line of cliffs called Pali.  In the other direction is the ocean.

Thank you both for the additional information. I do get the part about having to plan ahead and resetting the home point if needed but like I said I was hoping there was something I was missing.

Cetacean - What I don't get is you say maximum height 1640. The P4P has a service ceiling (unless with the new firmware upgrade that changed and the published specs have not) of over 19k'. I have a mountain near me that is 1600' above sea level and probably about that above ground level. I would not want to be on the ground looking up and be only 40' over it. So maybe I am misunderstanding something there.

Thanks again.
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Labroides
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jsantacroce@hvc Posted at 2017-6-8 01:52
Thank you both for the additional information. I do get the part about having to plan ahead and resetting the home point if needed but like I said I was hoping there was something I was missing.

Cetacean - What I don't get is you say maximum height 1640. The P4P has a service ceiling (unless with the new firmware upgrade that changed and the published specs have not) of over 19k'. I have a mountain near me that is 1600' above sea level and probably about that above ground level. I would not want to be on the ground looking up and be only 40' over it. So maybe I am misunderstanding something there.

Your Phantom has a hard limit of 500 metres above your launch point.
You can't fly higher.
If you went to the Himalayas, and launched from a high mountain, your Phantom could physically fly at up to 6000 metres - but you still can't go higher than 500 metres above launch point.

It's unclear what you mean by "having to plan ahead and resetting the home point if needed".
In post #4 you said "is there any way to determine the height above that hill or structure at that time without resetting the Home Point".
Resetting your home point won't help you in that way.
Why would you want or need to reset your home point?
There are occasionally reasons to do so but it sounds like you aren't thinking about those.
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DroneGuyEd
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Current consumer drones have no ability to measure actual distance AGL.  They get the GPS altitude at take off, which sets the zero point, and all height data is relative that that for the flight- obtained via GPS.

If you fly over a 200' hill, the drone knows you are at at least 200' altitude but has no clue (beyond using vision at low AGL heights) where the ground is below.  At some point in the future newer drones might have this capability, but I am unaware of any that do today.

If you take off from that 200' hill, you can go up 400.  If you then fly back towards the home location (down the hill) and go down, your attitude can show negative height if you fly below your take off point.  I dont think there are any current limits on the value of the negative values.

There is an 800' hill very near my home.  I could fly up 400 from the top.  I could probably also fly out a few hundred and gradually fly down and land at the house...a full 800 feet down (I'm not going to try that) as its completely in line of sight.  However if I take off from the house...I could not fly up to the top of the hill...using the same path...as that would require more than 400 from take off point.
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Labroides
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DroneGuyEd Posted at 2017-6-8 02:50
Current consumer drones have no ability to measure actual distance AGL.  They get the GPS altitude at take off, which sets the zero point, and all height data is relative that that for the flight- obtained via GPS.

If you fly over a 200' hill, the drone knows you are at at least 200' altitude but has no clue (beyond using vision at low AGL heights) where the ground is below.  At some point in the future newer drones might have this capability, but I am unaware of any that do today.

Except that the Phantom doesn't get height from GPS (which is quite inaccurate for altitude).
Altitude data comes from the barometer.
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DroneGuyEd
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Labroides Posted at 2017-6-8 03:15
Except that the Phantom doesn't get height from GPS (which is quite inaccurate for altitude).
Altitude data comes from the barometer.

Either way...the result is the same...its relative to take off point and not true AGL.
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Antonio76
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I'm not sure if this may be of any help, but I just discovered a feature in Google Earth that might come handy when programming a flight...
If you use the Ruler tool in GE, you can draw a single line between two points or a path made of linear segments, and save it, then you can click the mouse over it and a list of actions will show up, including  "Show Elevation Profile", which will open a window where you can move the mouse and an Arrow will accordingly move over the path or line. Note that elevations are all Above Sea Level, so some math will be needed to reduce values to AGL etc...
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Spyder3534
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Yeah GPS is not accurate enough for maintaining altitude.   My advice, zoom in on Google maps terrain view and read the contour line altitudes. The difference between your take off altitude and the altitude of you final destination can be added to you 400' ceiling setting.  
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jsantacroce
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Thanks all again but the Google Maps and contour line altitudes is what I was not aware of and the closest thing to what I need. Thanks for that. I can definately make use of that for what I want to do.

So my last dumb question of the day. What if any are the limitations of TerrainFollow Intelligent Flight Mode. If I am at my home point and set it for TerrainFollow to come up hill and I have it set if I can for 400' and it's a 200' hill and I have my max height set for 600', does it work? And if so, how does TerrainFollow then know how high it is above the current terrain?

Thanks again all!
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racer888
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The terrain follow mode will only work between one meter (3.3 feet) and 10 meters (33 feet). It uses the downward sensors to maintain the height you choose and you have to keep the forward stick pushed to keep moving. It works on gradual uphill terrain and will not automatically follow down slopes. You have to lower the drone down and supposedly it will stop at the height you set.
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jsantacroce
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Good info, thanks again. Too bad those sensors were not capable of following terrain to 400'

Thank you all again. This helps alot.
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Cetacean
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jsantacroce@hvc Posted at 2017-6-8 01:52
Thank you both for the additional information. I do get the part about having to plan ahead and resetting the home point if needed but like I said I was hoping there was something I was missing.

Cetacean - What I don't get is you say maximum height 1640. The P4P has a service ceiling (unless with the new firmware upgrade that changed and the published specs have not) of over 19k'. I have a mountain near me that is 1600' above sea level and probably about that above ground level. I would not want to be on the ground looking up and be only 40' over it. So maybe I am misunderstanding something there.

Aloha santa,

     1640 feet is about 500 meters and 500 meters is the computer controlled altitude limit for the Phantoms.  This is way under the service ceiling unless you are launching from 17,360 feet.  If you launch from the beach next to the mountain near you, you would have 40 feet under the Phantom when you summit the mountain.  If you launch from 175 feet above sea level on the side of the mountain like I do, you would have 215 feet under the Phantom when you summit and you would still be legal.

     You can set the MAX Altitude between 120 and 500 meters.  You can also set the MAX Altitude lower than 120 meters like I did to stay under the Marine Base Air Field altitude limit for sUAVs.  These are tools you have to help you use the numbers you figure out to allow you to stay legal.  

     On a related note, be sure you understand the various Return to Home altitudes and the effects of your actions on the flight home.  If you fly behind a solid object for more than 3 seconds your Phantom will disconnect and you may have a problem returning home unless you have the right settings.

     Hope this helps!

Aloha and Drone On!
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Cetacean
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DroneGuyEd Posted at 2017-6-8 02:50
Current consumer drones have no ability to measure actual distance AGL.  They get the GPS altitude at take off, which sets the zero point, and all height data is relative that that for the flight- obtained via GPS.

If you fly over a 200' hill, the drone knows you are at at least 200' altitude but has no clue (beyond using vision at low AGL heights) where the ground is below.  At some point in the future newer drones might have this capability, but I am unaware of any that do today.

Aloha Ed,

     You should be able to fly back up your 800 foot hill near your home as long as you stay within 400 feet of the hill (and as you note, line of sight).  Your Phantom is not limited to 400 feet from take off point or 400 feet above Home Point.  However, you are computer limited to 1640 feet (500 meters) above the Home Point unless you move the Home Point up the mountain by landing, shutting down and taking off again.

     The regulations, however do limit you to 400 feet of a structure and a hill is considered a structure.  If you fly up the hill and stay within 400 feet of the hill, you can fly up to 1640 feet above the Home Point while still within 400 feet of the hill (more like a mountain at that height!).  

     At least that is the way I understand your point in Post #13.

     Hope this helps!

Aloha and Drone On!
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DroneGuyEd
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Cetacean Posted at 2017-6-8 20:29
Aloha Ed,

     You should be able to fly back up your 800 foot hill near your home as long as you stay within 400 feet of the hill (and as you note, line of sight).  Your Phantom is not limited to 400 feet from take off point or 400 feet above Home Point.  However, you are computer limited to 1640 feet (500 meters) above the Home Point unless you move the Home Point up the mountain by landing, shutting down and taking off again.

Yes, I do understand that well.  If you do mod the 400' limit value, you can fly higher.  I prefer not to change that to avoid later issues if I forgot to set it back.

In my case there are way too many houses and trees on the path up (or down), so its not a flight I ever expect to try.
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Cetacean
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DroneGuyEd Posted at 2017-6-9 05:16
Yes, I do understand that well.  If you do mod the 400' limit value, you can fly higher.  I prefer not to change that to avoid later issues if I forgot to set it back.

In my case there are way too many houses and trees on the path up (or down), so its not a flight I ever expect to try.

Aloha Ed,

     Believe me, you are not alone, especially at our age!

Aloha and Drone On!
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