UAV for photogrammetry / surveys

Hi Everyone

Im putting together a UAV for aerial surveying using stereo photogrammetry.

Id like to get some input for the experts before going ahead.

My plan is to buy a high wing trainer coupled with an APM2.

Electric powered with a gyro camera mount.

The software Im using is photomodeler scanner. It can do DSM.

Im quite a n00b when it comes to fixed wing, but I have got a fair amount of expericence on multi-rotors.

Im doing this on a fairly tight budget and need to know a good camera to use.

Any advice would be greatly appreciated and will gladly buy any1 a beer if you're ever in South Africa :)

Thanks!

G:)

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Replies

  • For mapping you need a small quad and something like the Samsung NX1000 with a 16mm lens. No need for a gimbal! Since you are in South Africa, consider steadidrone.com equipped with APM2 or Pixhawk. This platform has a wide user base (for support) and is easy to repair and maintain. This advice is from practical experience.

    Another very good camera is the Sony Alpha 6000. See http://diydrones.com/profiles/blog/list?user=2amo6urztvqt6 for a robust quality test. We use Agisoft's Photoscan Professional.

    Make sure you have lots of well surveyed ground control - consider purchasing dual frequency GPS receivers such as the V-Map systems for this purpose - cheap and extremely easy to use. Can also be carried on the UAV (weight is 130g) to fix camera stations.  

    If I ever do swing by, make mine a Windhoek Lager - I don't drink Bud, Miller or any of the SAB varieties. 

    Walter Volkmann (ex Namibian Land Surveyor  - now in the US)

  • Has anybody using sony alpha 5000 or 5100 for aerial photogrammetry survey? Very interested hearing your experience on those camera. Sony5100 has 24.3 mp, 4mp higher than alpha 5000, but will it have significant difference?

    • Arga I have been using an a 5000 for about 6 months now, it is a good camera, Im using a 24mm sony lens. The camera we still use the most and you will be very surprised to hear this is an eos m,  we do stockpile volumes for corporate clients, the products we survey are black in colour to almost white. For our purposes we have found absolutely no advantage in trying to squeeze out extra mega pixels, we have run tests with cheaper 12mp cameras with good focal properties and results are pretty much the same as with higher mp cameras, BUT

      The thing to look for is a camera with good low light performance especially when you are doing stock surveys because the weather is not always ideal come month end, the a 5000 has pretty good low light performance even when using high shutter speeds, unfortunately we find the Sony very susceptible to dust, somehow it gets into the camera very easily. To answer your question, for survey purposes there will be no advantage especially if your survey areas are large, 

      • What we found was a step improvement in quality of model reconstruction when moved from using the NEX5 with a 24mm equivalent to the A7 with a carl zeis prime 35mm lens. Also the very old EOS 350D performed good too.

        • Hello Duffy, I have heard similar before, what sort of surveys are you doing size etc and altitude. I have considered going 35mm but would have to fly too high. What processing suit are you using and calibration software. 

          • Wayne,

             Most of the applications we tried the A7-35mm lens combo where for environmental surveys. So we have done coastal erosion work (volumetric and mapping analysis of sand dunes) and similar habitats, as well as analysis for forestry. Especially for the forestry the 24mm lens was no good at all. with the 35mm flying at 100-120m AGL it is perfect.

             Surveys are run with 70% overlap, using our RaptorE1 we have plenty of battery and speed (normally fly at 20m/s) to cover large areas.  

            Although have tested other software packages, Agisoft is winner. I know it is not as fancy looking as other packages but it does the best job in reconstruction as far as I am concerned.

             The next camera we will try in the A7r, not because we think it will improve quality of model but rather because we need thee higher ground resolution for some other projects. The A7s is ideal because of it's large size pixels which means you can shoot fast no matter what the light conditions.

             Regards

            • Hi Duffy

              I did a few tests with a rented A7R on my Skywalker last November.
              Zeiss 2.8/35mm, 90m AGL, 15m/s.

              Great pictures but I had to go for 1/4000s or higher. Not scientific
              work but for this resolution a cam with only 1/4000s may not be enough.
              Did someone make similar experiences?

              regards
              Wolfgang R.

              • Hi Wolfgang,

                 Why did you have to shoot at 1/4000?

                 I wonder if the problem was with vibrations and set of the aircraft rather than required shutter speed at that altitude/speed and lens

                 Thanks

                • Hi Duffy

                  I couldn't succeed with my first test flights. Then I stepped back to the ground.

                  Here I could do larger series of setup combinations. From within my car I tested with similar speed and distance. Lower shutter speed did not make perfect pictures on the pixel level. In the air this setup gave me series of more than 100 pictures without a single fail.

                  I started with 1/2000s. But this didn't hold for me.

                  As the car and plane tests behave similar I vote for the shutter speed.

                  But may be someone can convince me that it can't be true.

                  For the next time I don't have an A7R to test in more detail.

                  regards

                  Wolfgang R.

                  edited:

                  just found my original calculation I started with

                  ...

                  AGL: 90m =>  ground: 61.7m x 92.6m
                  pixel: 61.7m/4912pix => 1.26cm
                  1/2 pix size: 1.26cm/2 => 0.63cm
                  15m/s:   0.63cm/15m/s => 1/2381 sec

            • With 35mm focal length, 120m agl and 20m/s speed, would it be 1 frame per second or even lower? Are you using ir or usb trigger?

              Have you tried the zoom lens set at 35mm instead of prime lens?

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