Replies

  • Darius Jack November 9, 2015 at 4:40pm

    Lidar is an old technology, not fit for your purpose.

    Since fluctuations in altitude measured  (soft tissue at different altitude) result in error generated, can force your drone to collapse finally.

    You don't need old lidar since 3D video/ camera can replace lidar in your case.

    GPS is all what you need to keep altitude fixed if land is flat and even.

    High resolution camera gives better results (lens and angle) if you fly higher.

    Flying at low altitude makes you to fly many times longer since camera lens angle has its own limits.

    Just calculate sought resolution on the ground and selecte lens, camera resolution

    and altitude to match.

    Forget lidar.

    Lidar was used to scan the ground, landscape in 3D, replaced today by video processed into 3D imaging to extract Z-dimension.

    Procedure is fully computer based (off-line mode)

    darius

    manta103g@gmail.com

    • Cala > Darius Jack November 9, 2015 at 4:50pm

      Thank's Darius, land is not flat where I fly,  Video is not affected by plants?

      You speak to something like this?  http://www.hobbyking.com/hobbyking/store/__66308__HK_Pilot32_Optica...

    • Muhammad Al-Rawi > Cala November 9, 2015 at 8:37pm

      I don't quite agree with Darius regarding the use of 3D cameras over lidar. There isn't a need to complicate a relatively simple task. Lidar is becoming cheaper and better every day. Nothing outdated about it.

      The two simple, off-the-shelf options are sonar and lidar. 

      Sonar works well on hard surfaces parallel or near-parallel to the sensor. In terms of reliability and versatility, you generally get what you pay for. They can work over vegetation and rough surfaces, but only to an extent. Indeed they are unable to operate reliably over soft surfaces (which may include your vegetation). 

      Lidar works on most surfaces. I think it is the more robust of the two methods for your application.

      Here's an example of a similar sensor on a quadcopter. Keep in mind that this video is over 2 years old and things have improved since then: https://www.youtube.com/watch?v=3I06AOwIQVY I'm sure there are better videos out there, but this one immediately came to mind. 

      EDIT: Here's a more recent video of Lidar Lite in use (First 30 seconds): https://www.youtube.com/watch?v=FUT-ZsKGtxI

      The optical flow sensor linked above has a built in sonar for altitude. As far as I know, it primarily uses the camera for x/y positioning.

      I should add that I don't have experience using either sensor on a quadcopter. I have primarily used them in ground-based robotics projects.

    • Cala > Cala November 9, 2015 at 5:36pm

      Sorry, english isn't my language and I understand that you where speaking about optical sensor, I read again and now understand what you refer GLUP!! . The idea is that using a high res camera and low altitude try to detect damaged plants by insects, i don't need (in this case) to make mosaics, only to take photo samples with as higher resolution as possible (less walking, less time to monitor insects). Now I'm doing helped by FPV but is a risk to fly very low altitude. 

  • Cala November 9, 2015 at 2:55pm

    http://www.hobbyking.com/hobbyking/store/__87786__Ultrasonic_Module...

    What do you thimk about this one for this task? It says that not detect soft things, like plants?  "although acoustically soft materials like cloth can be difficult to detect"  and looks really cheap :O

  • Benny Shimon November 9, 2015 at 9:08am

    Hi Cala, that looks very interesting.

    can you pinpoint me for more information regarding the sensor?

    thanks 

    Benny

  • Alf Pettersson November 9, 2015 at 8:40am

    Hi Cala,

    I have flown using LidarLite and I think that it is functioning best when I fly below 15 m above the ground. I have not seen it been affected of vibration, possible it will be affected by changes in angel? If I fly higher than 15 m it seems that it has problems on some ground to get the altitude, but when lower normally no problems.
    Hopefully it will be implemented in more flightmodes, think it is just althold that uses it now?

    • Cala > Alf Pettersson November 9, 2015 at 8:54am

      I think that I read in any part that support Loiter too that only not support auto yet but that is only time. Did you fly over crops? 

    • Alf Pettersson > Cala November 9, 2015 at 11:37am

      Only over feilds with grass not like yours crops?

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