Question 1:
Im in the process of designing an airframe for aerial mapping to create orthomosaics, point clouds etc etc..(When I say designing, I mean researching and putting a list of parts together for prices/weight etc.)
Im considering using a techpod with a sony nex 5 in the fuselage, but am just wondering what options there are for pitch and roll stabilisation? Will APM2.5 or pixhawke do a good job of controlling the stabilisation, or will I need to use a separate controller?
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Question 2:
Also, I need some help on calculating the height of the aircraft
The formulas im using are as attached in the spreadsheet. What I need help with is understanding the difference between focal length (f) and Focal length in 35mm equivalent (f35).
The formula I have been given to calculate f is (f35*Sh)/34.6, where Sh is sensor height. I guess im just looking for a reference to this formula, where the 34.6 comes from and what the correct figure is for f35 for a Sony nex5.
Currently for f35 I am using a multiplication factor of 1.5 which I got from here (LINK) by dividing the "Eq. focal length" by the "focal length" as shown in the lenses table. So for Nex 5 f35 with a 16mm pancake lens f35=1.5*16=24mm
With my calculator (attached) the height of the aircraft for a Nex5 using a 16mm pancake lens to obtain a GSD of 5cm, I need to be at 113m AGL. Does that sound right?
Thanks,
Nicholas.
Replies
Was wondering how you shortlisted the Nex5 and not the Nex7 here ?
I am looking to build a similar airplane and torn between choosing one of the above cameras !
Ooooh, keep us posted! I've got an NEX6+20mm lens that I'm trying to find the right fixed wing platform for, and the Techpod is one of my top choices. I'd love to see if you come up with/track down any roll stabilization mechanisms for this combo.
Though I wonder if stabilization is even necessary? With such a huge wingspan I'd think the Techpod would be fairly stable in the air. Shoot at a high enough shutter speed and motion blur from little wing flutters shouldn't be an issue either.
As for your calculations, you should download Mission Planner. It's got a great orthophoto calculator built in. Input the sensor size, resolution, focal length, and desired GSD and it'll tell you your target altitude.
Question 1:
Yes - gimbal control is standard and works very well on Ardupilot. You might find you only need a single axis (roll) gimbal. Pitch angle may be relatively minor when you are at your cruise altitude, this may save you some space and weight in your airframe.