Few questions after first mission

[zzmike76]

Hello all

Today I went out in the Mountains for my first "real" mission and written down some questions which hopefully you can help to clarify :

- as soon as I turned on the AC and RC, a message appeared claiming there were magnetic interferences and I needed to re-calibrate the compass. As far as I understood, if you move in a zone which is more than 100 km far from your previous GPS location, you need to anyway re-calibrate the compass. However I am not sure whether in this case there were "really" interferences (I was surrounded by rocks and ice/glaciers) or just the distance > 100 km applied. any idea?
- despite having checked multiple times I could fly in the area, when I took off I had to manually confirm a warning stating I was flying in a protected area (did not record the message but was claiming something about airports, which of course were faaaar away from the glacier)
- I kept having a look at the receiving signal which was almost always between 4 and 5, but it happened twice that all in a sudden I lost the connection (and some years of life ? ) and the AC forced a RTH with 20/30 seconds of "silence". Is the radio signal similar to the mobile gsm one (which can go away in seconds in the mountains) ? Would in this case a mod (e.g FCC) have helped (just for my understanding) ?
- I was flying over the glacier basin (water), but I did not get any warning about the altitude above water , and since I was a bit below the RTH altitude (hence negative values) I am wondering whether the AC would have just splashed in the water or not ?
- related to the previous question , if I send the drone below the RTH altitude (e.g in a valley), will the drone just apply the RTH altitude (and possibly crashing) or consider also the delta value when coming back?
- is there any way to see at which time the battery was changed in the metadata ? I was very quick in changing them so now have some issues in identifying the right times.

Many thanks to all and have a nice flying weekend from Switzerland
Michele

 

[DanMan32]

Displayed altitude is relative to takeoff and is determined at least mostly if not completely based on barometer readings. I have noticed altitude drifting a lot from true value, but not more than 10ft. VPS altitude is accurate on land close to the ground, within 30ft if memory serves. VPS will give mixed results over water.

If RTH is triggered, AC will fly up to set RTH height unless you're flying above it. Rules change within 20m distance from home point. Obstacle Avoidance can handle obstacle issues during RTH, but it's not 100% so don't rely on it completely.
You may want to read through the user manual available on DJI's website.

Flight logs will include battery serial number used during flight. Instructions can be found on PhantomHelp website. Posting a link to the results can help us answer some of your other questions.

 

[zzmike76]

If RTH is triggered, AC will fly up to set RTH height unless you're flying above it. Rules change within 20m distance from home point.

So for my understanding, if I takeoff at 2300 meters (and with 100 meters of RTH height), fly down to 2250 , when pressing the RTH button the AC will go to 2350 or 2400 when coming back ?

 

[MAvic_South_Oz]

2400m

 

[DanMan32]

2300M MSL (Mean Sea Level) would start out as 0 ATL (Above Takeoff Level) from the AC's perspective. If you descend 100m down a cliff, ATL would show as -100m, actual 2200m MSL.

Do consider the AC altimeter does drift, sometimes as much as 10M though I don't think mine has gotten off by more than 10ft. Usually in the negative, meaning just as I land it may show -10' when it should show 0.