Flying in a straight line over hilly area, will the drone maintain height above the ground

Will the Mini2 change its height as it moves over new hilly ground and maintain preset height above “current” ground level or will it fly straight at the preset altitude maintaining height above starting point. Let me clarify by example. If you climb to 100ft and fly into slowly rising open ground that rises to 30ft above your start point, will the drone rise to continuously maintain 100ft above it’s current position which I think desirable, or can it only continue straight and flat with reference to the start point which would mean it is now at only 70ft above the ground. If the latter, then to continue the example, if you flew it into the side of a 200ft hill the drone would, in effect, seem to be descending until it got to a height of a few feet where the collision sensors on the bottom would prevent destruction. The Mini2 has GPS of course which should sense height as well as location. That’s useless pretty much for a drone flying a few hundreds of ft above the ground so I think the height is maintained in reference to the ground level but I would like to here what more experienced drone pilots think would happen in my example question. Thanks Geoff Heap PP

This has been covered so many times; please try performing a search if you have other questions.

So this will be quick, NO DJI Drones have an altimeter. They do not know what the altitude is, be it death valley (282’ below sea level…) or from the top of Mount Whitney (14,500’ above sea level…).

**When you energize the motors on a DJI drone to take off, that point is “Ground Zero” **

When you lift off and it is even with the top of your head, it will think it is (your height high…), say 6’ high (as measured by the distance it rose about the land pad) and that does not matter where in the world it is.

If you then fly straight, it will always think it is 6’ off the ground. If you fly off a cliff, it will still think it is 6’ high or off the ground even if the cliff drops 1,000’…

If you are in a valley and fly towards a hill or mountain, you had better raise it higher yourself because it is not going to do it for you, and if you blindly fly it forward, expecting it to stay 6’ off the ground, you will be sadly mistaken when it runs into the ground.

Now, go watch lots of YouTube Videos and learn how to fly your drone vicariously, watching and listening to the folks who know their stuff. If you are in the US, have you gotten your TRUST Certificate?

And do you even know what the laws are for flying a drone in the US?

Drone Laws and Best Places to Fly in Every US State - Pilot Institute

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Thank you “Loud Thunder” for reading half of my post. If you read it again with a little more attention you’ll discover that I already knew that this was one of two possibilities. I merely needed to know which was correct, and why, which you did not address. Again, if you read it thoroughly you will see that I understand the “Flying into the mountain” thing. Thanks also for letting me know that I have to read every FAQ before posting my first ever question. I did make a good faith effort to search for this subject but did not find enough detail. I still would like to know HOW it maintains the altitude. As originally stated I know the Mini2 has GPS. Sooo now I’m thinking that I may know the answer to the “Maintain” part of my question. I forgot about this, the Mini2 will, in certain situations, rise to a safe preset altitude and fly home (start point). How can it do this? It must be that the drone is using the height supplied by the GPS which I was not sure about but now I see it makes sense. Again, please I would appreciate further comments on this interesting subject from members. Surely it doesn’t matter that it’s been talked about before does it. This IS a forum, yes? So now I think I’ll try again to find some more posts on the subject but I would still appreciate your comments here guys, thank you. So “LOUD THUNDER” (Good username choice). I did study everything I could regarding drone safety after purchasing my Mini2. I know about the certificates that I can get from the FAA and other drone flying organizations and intend to comply. Before and after my first flights I did, and continue to watch lots of videos to be safe. These drones are not cheap. Finally, yes I do know the laws regarding flying drones in the US. Just as I understand thoroughly the laws regarding where I can fly my aircraft. I hold a Private Pilot certificate and currently fly my own Plans-built 2 seater cross country CH 701 from Zenith Aircraft company of Canada. However I don’t know it all yet so I came here to find out a bit more, Not get my head bitten off. Geoff Heap PP

How on earth did you ever manage to get a Private pilot’s license if you do not understand the concept of GPS Altitude and altimeters? You don’t need to answer, I’m not really interested since you did not really read my response to your question in the first place… because if you had you would have said, “Hey, he’s right, I should have realized that in the first place…”

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Cheddar Man,

Some of what you say is right, some isn’t. The barometric pressure sensor in the Drone sets the altitude to 0 at takeoff if you have GPS or not. If you fly in the house, the Infrared sensor does most of the work as the barometric sensor is a lower priority as DJI knows any flow of air, even the prop wash changes the air pressure, a fan, forced air heater, an Air Conditioner vent all affect ambient air pressure. Study Boyle’s Law on Thermodynamics…

When you are outside with weak GPS the Infrared sensors again take priority and will restrict the max height since the sensors become less dependable as the height increases. The max height is dependent on the various models, based on location of sale, you mention the UK, it might be different in the US.

DJI references 5 meters with good Infrared and 30 meters with poor infrared reception…

Now, concerning your last paragraph… In Truth, the maximum height you can fly is no more than 400ft/120m above the surface (in the States we say "Above Ground Level (AGL)…). So, if you take off in a valley and fly up a steep hill and keep your drone in line of sight, it does not matter if you have climbed over 1,000 feet up as long as the drone is less than 400 feet above the ground.

To put it another way, if you tied a 400-foot long piece of string to the drone and the string dangles down and always touches the ground, it does not matter how high the drone has risen…

When you take off with good GPS, the barometric pressure set 0, and the GPS locks that location as the home point or until you reset (you would want to do this if you are traveling, like hiking, bicycling, boating, etc…). But no matter what you do with the Home Point, the original 0 point remains until the drone is landed and the motors reenergized.

Now a point about negative height. When you take off, the launch point is the 0 point. If you took off from the roof of your house and flew down the ground, the reading would be in the negative range, that “10 -meters” is not an altitude, it is only a reference to the difference between the drone location now and when it took off…

If you are in the Scottish Highland and you take off from Glen Shiel in Kintail and raise your drone just over your head to 2-meters and then started flying straight out to Ireland, you would quickly be thousands of feet in the air but your controller would still read 2-meters, but really in violations the Civil Aviation Authority…

Besides Boyle’s Law…

You might want to brush up on your own countries’ laws

Please disregard my comment stol, seems I was wrong!
By the way, I do know the UK laws!

So now you want to talk about GPS altitude by way of insulting me again. You never talked about it before even when I brought it up. What you said is this “THE DRONE DOES NOT KNOW WHERE IT IS…” But yes, of course it does. It knows its longitude and latitude and its height above sea level. And according to tech support it is displayed on the Map screen. Again, you say this again “They do not know what the altitude is, be it death valley (282’ below sea level…) or from the top of Mount Whitney (14,500’ above sea level…” See. You’re WRONG WRONG WRONG the drone knows its exact height ( and location ) above sea level at all times that it is receiving signals from the satellites. So this guy LOUD MOUTH, SORRY, LOUD THUNDER, insults not just me but another guy (CHEDDARMAN) from the UK who tried to be helpful. Loudmouth instructs Cheddarman on Temperature/Pressure situations like he’s a 5th grader and then tells him to read up on UK drone law. There is no limit to loudmouths ego. He should read something himself. How about the guide for online behavior which pops up when you post. The first suggested rule is, Be kind to your fellow community members. You know I read a lot of his posts and He told one guy "there is no stupid questions, there are only stupid people who don’t ask questions. Wind the clock back to my first post. I don’t think it was a stupid question. I just wanted to clarify something. He was rude from the getgo. He said Now, go watch lots of YouTube Videos and learn how to fly your drone vicariously, watching and listening to the folks who know their stuff. If you are in the US, have you gotten your TRUST Certificate?
And do you even know what the laws are for flying a drone in the US? Excuse me.This guy just assumes nobody knows anything or looked anything up. So what if they did, that’s no excuse to be rude and insulting. Geoff Heap

Somehow I managed to satisfy the FAA

You seem to have missed the entire point of all this… Yeah, the drone may know where it is, but that data means nothing to the drone, all it is x,y,z (Latitude, Longitude, and relative height). I say relative height because it does not know what altitude it is at MSL, which is why it lists 0 as it’s altitude when launched (motors energized). If you throw the drone out the window of an airplane 2,000 AGL, at that moment the drone thinks it’s at ground 0, the same as if you launched it from a mountain top. So for all intents and purposes it does not know where it is; except that’s its reference is “here”

The same as if you are blindfolded by your friends for a surprise birthday party and they take you into the woods, would you know where you are? Yes you would, you are right “here…” But where is here, well that’s another matter, just like the drone…

You wanted to know if a drone would fly up a hill based only on its own resources, it can’t! It only knows that it’s “here” and it does not know if there is a wall, a tree, a hill, or even a mountain in front of it…

You say you are a pilot, but don’t you know that when you fly, you have to often reset the altimeter based on the local barometric pressure? Perhaps I missed that chapter in the user manual on setting the barometric pressure. So how would a drone know its altitude? As I said, the barometric sensor on the drone only help to establish ground zero…

Pout, Shout, Stamp your Feet all you want at the perceived indignities you believe you’ve received, but I can see that none of it changed your attitude; which is like your drones altitude when it flies into the ground, it’s low… And you called me insulting, I never made fun of your user name…

So, my parting advice is: go out, fly your drone, but stay away from any hills as that little bird does not stand a chance with you as its pilot…

Can we please stop this. Yes, I do understand the drone will not rise to follow rising terrain. At the time of my original question, I mistakenly thought that the drone had more capable ground sensors. I now see that’s not the case. The bottom sensors are just for deceleration when landing. Thank you for that, but you just did it again. You said I say relative height because it does not know what altitude it is at MSL”. YES it most certainly does. When it is receiving signals from at least 3 of the 12 or 15 GPS satellites it knows its exact height above Mean sea level. Yes, it will show a height of zero at power up but that’s just a convenience for us human operators. You like to give examples so let me give one. If you are at a height of 100ft above sea level and power up your drone it will give you a relative height of zero. After a few seconds it will see that it is at a height above sea level of 100ft. Now, its not going to tell you that and confuse the issue because you probably don’t care. Now if you raise the drone 15 ft the readout will increase as you rise and show your height as 15ft. Great. But it knows that its sea level height is 115ft but again its not going to tell you that and confuse you the operator. However, as per Dji tech support, if are curious you can go to the map page and see the MSL height. Now. You have referenced a couple of times a barometric sensing device in the probe (Dare I say altimeter) I can’t find reference to it in the comprehensive tech specs on the Dji site, so I have a question in with them about it. Waiting for a reply from Sherry.

Bye the way one of your favorite examples is Launching the Mini 2 off a mountain and you seem to think that at power up the drone will show a height of Zero. I agree. But if that mountain top is at 13,200 feet or higher the drone will not climb. It doesn’t matter that the local height reads Zero. It also doesn’t matter that the drone knows its true height above sea level. 13,200 ft is the service ceiling for the drone. Service ceiling is defined as the max height you can reach at max power before it climbs so slowly that its struggling and a waste of time. You can get a few more feet but it’s pointless. If you launch at much above 13,200ft say goodbye to your drone. So yes, I understand that if you throw a drone out of a window of a plane at 2,000ft your controller will say that its height is zero. Nevertheless, the drone knows is at 2,000ft MSL. You can make fun of my username if you want to. And I’m not pouting or shouting or stamping my feet. I’ve come to realize that your insults are your defense against someone who knows a bit more than you do. I say I’m a FAA certified pilot and without knowing the first thing about me you attack my knowledge of flight and my piloting skills. What does that say about you. I know what I think. Geoff Heap, PS why don’t you sign your posts. LOUD THUNDER!!!. Gimme me a break.