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[Zebra48]

I am new to drone flying and am still getting my head around the various restrictions and recommendations. (I have registered as an operator and a flyer with the CAA and completed their online test.) As I understand the regulations, I am permitted to fly a drone up to an altitude of 120m from the ground on which I am controlling the drone/ where it takes off. One of the areas (moorland) from which I hope to fly my drone (take-off location) is at an altitude of 110m approx. So technically I could fly the drone upwards for a further120m, resulting in it being at an altitude of 230m above sea level, although only 120m above the take-off location. Am I correct? Have I understood the regulations correctly?

In the above scenario, is the RTH figure (e.g. 60m ) the height above ground or above sea level? I've had conflicting answers to this question. If the height for RTH is above sea level, then I would need to set the RTE height at 140m approx. Hopefully the experienced members of this group can give a little clarification. As you will understand, I just want to get it right.

 

[Starz]

Any RTH number will be measured from your takeoff point. If you set RTH at 70 meters, it will RTH at 70 meters above your home point.

 

[Starz]

So technically I could fly the drone upwards for a further120m, resulting in it being at an altitude of 230m above sea level, although only 120m above the take-off location.

Correct.

 

[SkyeHigh]

The aircraft and controller do not use Mean height above Sea-level (MSL) and only use height above the take-off point. It’s one reason the word Altitude is rarely used as that would normally be a relative measure to sea-level.

The height above take-off is calculated by the change in air pressure by a barometric pressure sensor in the aircraft. It takes a reading prior to take-off as its reference and as the aircraft climbs atmospheric air pressure reduces in a known way allowing the aircraft to calculate its approximate height (within a few metres) from the take-off point. From 30-metres and below the aircraft uses an infrared sensor to bounce light off the ground and measure how long it takes to reach the aircraft. This is more accurate than using the pressure sensor but can be affected by very bright, dark surfaces, water (especially moving water), wet or highly reflective vegetation and vegetation being blown around by wind. Trees being just one example.

 

[old man mavic]

@Zebra48 firstly welcome to the forum,
the max permitted height is 120m above ground level where the drone is flying ,the height that is displayed on the device screen, is from the home point where you first took off from
the RTH height that you set before flying is determined by you doing a pre flight check, of your surroundings to see what obstacles there are in the area where you intend to fly
this will determine what height the RTH needs to be set at
if there is very little tree cover and no tall structures such as electricity pylons where you are then you can set your RTH height accordingly, where i mostly fly then a good starting point is 40m as that will clear any of the pylons and tall trees around ,as you will be aware the wind speed tends to be higher as the drone goes higher so you only want your RTH height to reflect this ,always check your surroundings before flying and follow the drone code

 

[Laborous]

Welcome to the forum from the beautiful woods of Maine!

 

[Ron Anderson]

I am new to drone flying and am still getting my head around the various restrictions and recommendations. (I have registered as an operator and a flyer with the CAA and completed their online test.) As I understand the regulations, I am permitted to fly a drone up to an altitude of 120m from the ground on which I am controlling the drone/ where it takes off. One of the areas (moorland) from which I hope to fly my drone (take-off location) is at an altitude of 110m approx. So technically I could fly the drone upwards for a further120m, resulting in it being at an altitude of 230m above sea level, although only 120m above the take-off location. Am I correct? Have I understood the regulations correctly?

In the above scenario, is the RTH figure (e.g. 60m ) the height above ground or above sea level? I've had conflicting answers to this question. If the height for RTH is above sea level, then I would need to set the RTE height at 140m approx. Hopefully the experienced members of this group can give a little clarification. As you will understand, I just want to get it right.

The RTH is relevant to the take off position so... If you take off at 150m above sea level with a RTH set at 50m (relative to Take Off) then your drone will rise to 200m above sea level but at 50m relative to TO, will still be within the limit of 120m above the take off position. If you are on the moors and happen to fly over a hill which is 200m away from you and is 75m high then your RTH would have to be set at around 90m so that the drone would fly over the 75m hill. Hope that makes sense ?

 

[WJbdB]

It´s quite clear, maximum flight level is 120m above the ground level where the drone is flying at any moment. Take off level has nothing to do with. Flying uphill means you can go higher with the terrain and when downhill you have to lower you altitude. So flying above terrain is flying within the 120m directly over the drone´s ground projection.

 

[Starz]

It´s quite clear

Post number one(the original poster)was asking for clarification. What is clear to some, may not be to all.

 

[Zebra48]

Thanks to everyone who responded and for the welcome to the forum. The answers were very helpful and have clarified my understanding.