Replies to This Discussion

Permalink Reply by Chris McNair on June 3, 2010 at 7:22am

Depends on height, speed and FPS of camera system. Seems 75m at 60kph is good for 30FPS.

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ModeratorPermalink Reply by Gary Mortimer on June 3, 2010 at 8:25am

Ground speed has two speeds don't forget, into wind and downwind.

If your after overlapping shots for stitches you will need to think about that as well. Twenty seconds at 60kmh with a 40 kmh following wind you will have covered a fair bit of ground in that time.

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Permalink Reply by Rory Paul on June 3, 2010 at 8:28am

Unfortunately if you fly legally at 400 ft the interval between images can be very short if you allow for overlap. For best results this can be as much as 50%. So your camera / memory needs to be fast. Take into account that it needs time to focus and this is effected by the amount of light and the speed / movement of the aircraft.

There is nothing worse than running a flight and finding that you are missing images.

Good luck

R.

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Permalink Reply by Krzysztof Bosak on June 3, 2010 at 10:03am

@Condor "the amount of light and the speed"
...on the other hand the speed of light doesn't matters much.

For me, a photo every 1s is performing at 122m=400ft, every 3.5s is only moderately good at 200m.
Another solution is to fly each leg twice, exactly against and with the wind, just to counter that 'missing
overlap problem'. i would focus on cameras that can give indefinitely 1.5s shoting interval.
Yes this will limit the choice a bit and rules out RAW image mode.
IMO burst action is not useful as you need a burst of 100+ photos in order to cover reasonnable area.
Also note that on pocket cameras, the trigger interval is often shorter when using mechanical trigger, than when using electronic means (not a rule).

Yet another solution is to focus on slower-flying UAVs, like in the range 40-50kmh. This will reduce max operational windspeed to less comfortable 20km/h, but increase stitching success rate ;-)

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Permalink Reply by Bart on June 4, 2010 at 8:22am

Thx everybody!
@Krzysztof : what camera are you suggesting/using?

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Permalink Reply by Krzysztof Bosak on June 4, 2010 at 10:04am

canon have nice CHDK interface.
on the other hand they are heavy.

May I suggest fixed zoom, possibility of full manual mode, possibility to disable auto power switch-off, bright (large) lenses capable of accomodating polarising and UV filter, continuous shooting rate below 2s (preferably 1s or less).

Lenses shoudl be physically sturdy, not retracting, if possible (landing damage, never able to verify if it is already off or on)

Anything you find would be good, I was thinking for Canon G9-G12 but those are heavy ones (only UAV with 4-5kg AUW).
Maybe some Leicas?

Anyway all depends on your motivation. semi-pro results with simplest pocket canon triggered by a servo at 9mpix are reality.

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Permalink Reply by Brian Wolfe on June 4, 2010 at 9:42am

Some cameras also have the option of locking the focus. I lock my focus to inf. and it reduced my cycle time form approx 3 seconds to 1 second.

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