Anderjon
lvl.3
Flight distance : 666893 ft
United Kingdom
Offline
|
400 feet = 121.95 meters (400 / 3.28). If you're flying up to 140m AGL, you're flying at 459.2 feet. Personally I like to lock in 120 meters as my upper limit to be confident I'm legal (same rules here in UK :-)
On a general note, altitude means your vertical distance above mean sea level (MSL) and its calculated either by reference to the regional barometric pressure setting (which changes constantly) or, if you're a full sized aircraft flying high enough, a standard barometric pressure setting of 1013.25mb. In both cases you need to have the ability to manually adjust the barometric reference on your altimeter (plus a live source of barometric data).
Height on the other hand is your vertical distance measured in reference to a point on the ground. This can be done either by using a barometric reference, VPI or GPS.
Since there's no way to periodically adjust the barometric reference point in a Phantom, we can't use altitude (and it probably wouldn't be very useful to in the vast majority of cases anyway), so instead the drone automatically references the pressure at our take off point (once) and it uses height instead. Lots of factors affect the starting barometric reading the phantom takes and after 20 minutes of flying, minor changes in the barometric pressure where you are located plus heat from the aircraft and its battery mean the height difference between take off and landing can be larger than you'd expect.
Happy flying all! |
|