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Inspire 1 - Lightbridge and Optical Flow performance

Dec 8, 2014
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I pre-ordered my Inspire 1 almost a month ago, can't wait to get it like most of you.

This will be my first FPV-enabled quad. I've obviously always flown with line of sight. I'm not worried about getting disoriented with the Inspire 1, but I'm wondering what performance I should expect from DJI's Lightbridge, especially when I lose LOS. Will I be able to fly reliably over hills and small mountains? Will the video link be maintained in these conditions? Also, does anyone know if Optical Flow will be used to establish ground level when the Inspire is measuring/maintaining its altitude? For instance, if I were to send it to the other side of a small tree-covered mountain of let's say 300ft high, and then lost my signal to the unit at that point, would it return maintaining an altitude of 75 feet (as I specified in the PilotApp settings) relative to the mountain's surface or tree tops, avoiding to collide with them on its return flight?

Thanks all.
Ref page 59 of the draft manual, the Optical Flow system works only within 2 meters of the ground, so no.

Failsafe and return to home modes do not use the Optical Flow sensor anyway, only barometric altimeter. If you operate in a country where it is legal to fly beyond line of site, your best option would be to set your failsafe/return to home altitude to 375' to clear an obstacle that rises 300' above your launch altitude.
2.4GHz doesn't "bend" much. Performance through trees is weak, performance through mountains is nonexistant. 2.4GHz is better than 5GHz outdoors, but you are still restricted mostly to line of sight (though the RPV may be a very tiny speck at maximum range). Lower frequencies perform much better "around" obstacles (that's why LTE is mostly being implemented in the 700MHz range).
I'm surprised that Optical Flow only works within 2m of the ground. I would interpret that as saying that the Inspire will rely on Optical Flow in that range to automatically deploy the landing gear, automate takeoff and landing. But I understood its function to also be to substitue for GPS in indoors environments, and to do that it has to operate beyond 2m above the ground. How would it be useful when I fly in an indoors soccer field or ice rink? Additionally, the sensors underneath Inspire look like ultrasound emitters/receivers which could/should have greater range than 2m.
It has optical and ultrasonic yes. I understand that you need much bulkier equipment to drive optical sensors capable of greater distances. Ultrasonic on the other hand does not need much. The question again... what will be left for the Inspire 2 if they spoil us with everything from the start?
Actually, it is the other way around. Building an ultrasonic sonar system powerful enough to work much beyond 2 meters would both be prohibitively heavy and would torture animals for a much larger radius.
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