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Math?

Discussion in 'Pro/Adv Discussion' started by Sammynels, Jun 13, 2015.

  1. Sammynels

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    Ok so I am proposing to the use of UAV's to my Fire Department. I need help with math... When the P3 (for demo purposes, not the intended UAV for fire ops) is up 400 ft, what is the approx viewable area on a clear delay in optimal conditions on a stock machine? I know it may be hard to answer but I need to go in with some numbers along with photos and video... Thanks ahead of time, I love u guys
     
  2. Mal_PV2_Ireland

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    Go up 400ft above a road maybe, take a snap and then drive the length of the road in view?
     
  3. loganintx

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    You can see the moon on a clear night and the sun on a clear day. Both of those things are VERY far away. Your question is kind of dumb but it depends on the size of the object you're looking at. The camera doesn't have a maximum length of view. It records the light that falls on the sensor after that light reflects off of objects or is generated by them.
     
  4. loganintx

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    Are you pointing the camera straight down? Just use a field of view calculator
     
  5. Foosy

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    I am going to assume that you meant going up 400ft and aiming the camera down. The FOV of the camera is 94 degrees so you have a cone of 47 degrees around the axis centered in the drone facing down. You get 400x tan47=429 ft radius of coverage. Now assuming you are in a 4x3 view mode, you would have a diagonal of 858ft, and with the 3x4x5 rule, it means that your area of coverage is 686ft x 514ft

    Hope this helps
     
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  6. DrChris

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    This is from about 400 feet. It should give you a good idea...

    DJI_0315.JPG

    BTW, my daughter's high school is resurfacing the football field this summer and I agreed to take some shots of the progress a few times though the summer.

    Chris
     
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  7. jlo

    jlo

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  8. Sammynels

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    Ok. That's was I was looking for. Thanks Logan, it seems you compensate your lack of mathematical skills with your intellect. Right on!
     
  9. Buckaye

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    well - the curvature of the earth has something to do with it too...
     
  10. ianwood

    ianwood Taco Wrangler
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    Props to Foosy for actually knowing the math.

    One day, da interwebs gonna break and nobody gonna know how to do nuthin!
     
  11. taroh

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    From FPV, I think 4:3 mode seems to be cropped 16:9, and FOV 94 deg is based on 16:9. When radius 429 ft, 16:9 covers 748 x 420 ft area, then 4:3 covers 560 x 420 ft. Small correction. ;)
     
  12. Foosy

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    Actually you are wrong. The native sensor is 4x3 with max image resolution at 4000x3000. It is the 16x9 mode that crops the top and bottom.
     
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  13. ctp

    ctp

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    Yep! 4:3 photos come out 4000x3000, 16:9 are 4000x2250. Take two photos from the same spot and it's obvious 16:9 just crops 375 rows from the top and bottom.
     
  14. taroh

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    Oh really? Sorry :p
    However, which side is cropped is another problem than which proportion DJI measures the FOV. I have other 20mm lens but felt 4:3 is narrower... later I'll measure it.
     
  15. Foosy

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    The FOV is a specification of the lens, not the sensor. The FOV represents the cone of the image projected. The sensor lays within the projected circle. In this case they used a 4x3 sensor. Some companies use a 16x9 sensor and yet others use a sensor in between so that they crop horizontally to achieve 16x9 and vertically to achieve 4x3. In cameras with image stabilization a larger sensor is used and image shifts are corrected.
    Bottom line is each camera does something different with the sensor.
     
  16. taroh

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    ??? FOV is defined by both lens and sensor. Using the same lens, different sensor (film) has different FOV. Usually FOV (diagonal FOV) is defined by angle from the center at focal length to the top-left & bottom-right corner of the sensor (film).
    https://en.wikipedia.org/wiki/Angle_of_view#Measuring_a_camera.27s_field_of_view
    I have some 120 (6x6) lenses but using adapter it can be attached to 135 camera. The same focal length, but FOV (shoot angle) narrows.
    However, I also think 4:3 FOV 94 degree may be right... DJI proud of wide lens, and narrower FOV (if cropped 16:9 FOV is narrower than 94 deg) is not suitable for ad, by commercial principle. :)
     
  17. taroh

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    Sorry thread owner, hope this rigorous discussion won't let the fire dept. miss the house at the very edge of the picture burning...:)
     
    #17 taroh, Jun 17, 2015
    Last edited: Jun 17, 2015
  18. bobmyers

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  19. ctp

    ctp

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    On topic - Here are some examples of view at 200'

    Off topic - Rather than speculate, do some research. Park the P3 at one spot and take two photos, one at 16:9, one at 4:3

    DJI_0113.JPG DJI_0114.JPG
     
  20. happydays

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    Which one's which?
     
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