New Flyer - Active Track Altitude Concern

[Mavic Johnson]

Hello! I'm a new Mavic owner and very much enjoying the learning process, both in the air and on the forum. I've been staying close to home, taking baby steps to try and gain some confidence. Last weekend I tried out some of the intelligent flight modes with mostly expected results, however, on one trip I started the Active Track with the AC at roughly 70 feet, plenty of clearance to all possible obstacles, as the target began to move and i watched the screen I failed to pay attention to the altitude readout but noticed some approaching trees and noticed the AC had decended to about 35 feet with no input from the RC, I took manual corrective action and other than an elevated heart rate, no harm. I've attached the entire log that shows the many times I was in Active Track, but beginning at 903000 mS as soon as the Mavic accelerates it begins to lose altitude. I've read and watched many tutorials on Active Track before and since and I always took away that altitude remained constant (unless in Terrain Follow). Any thoughts would be appreciated.

 

[Vegasrobbi]

Unfortunately the Mavic does not use dynamic altitude in AT, this means the on board barometer tries to maintain a constant altitude. Problem is if the terrain rises the Mavic will lose altitude relative to the ground. If equipped with dynamic altitude Mavic would rise with the controller/device if it were supported but GO 4 does not.

What Mavic will do is use VPS when it gets close to the ground and correct "up"(1/2 terrain follow) so it does not hit the ground; however, VPS altitude will not correct "down" so if your going down a hill Mavic will continue to gain altitude vs the subject. VPS range is about 10 meters, above that it is useless and uses the barometer. My observation is the faster you go the more altitude you will lose and at the higher speeds VPS altitude is not reliable do not depend on it.

Same holds true in GPS follow, Mavic has poor altitude control. Apps like Litchi boast dynamic altitude but I have not been able to get it to work properly.

 

[Mavic Johnson]

Thanks for sharing your knowledge Vegasrobbie! Your explanation describes exactly what I saw.

 

[colinfowler]

my 1st active track video taught me to keep control of altitude myself and it works well.
as with all the mavic aids they have there limitations.
as said once you set off the altitude will stay constant with your start altitude. any rise or fall of the ground level will not be compensated for (as well explained by vegasrobbie)
i also found that disabling revers it active track will stop the active track backing you into anything (no rear sensors)
see the first run in my video as the horse gets close to the corner of the field the ground has risen and the sensors kicked in and it avoided hitting the ground, but continued to follow it then regains its track and continued as i controlled the altitude.
hope this makes sense.

 

[Mossiback]

Active Track is cool but also a major cause of crashes. The Mavic will cut corners and end up not pointed in the direction of travel, which negates the forward anti-collision sensors. Make sure there are no trees/wires/etc around and you are not going uphill.