Hi,

We did an inspection of a bridge with a DJI P1 camera (35mm) mounted with the upward gimbal on the top of our DJI M300 RTK.

The weather was good: not to much wind and a clear sky. We took photos underneath every 2s, concentrating to follow straight lines to have the best ones with overlaping. We put the best settings for the ISO, Aperture and shutter. And flying at around 11 feet away from the surface of the span (underneath).

When we analysed the pictures, it was impossible to see/find any crack correctly (like blurry).

So we did another flight taking pictures manually doing the focus manually: moving the drone to 1 foot by one foot, and adjusting the focus manually before taking the picture. Which is not the best with the size of the spans to cover.   

Any advice please?


Thank you

Hi,
In my opinion, P1 isn't the right tool for that kind of job. It might be better to use a H20. Even a M2 or M3 could be better. Its a question of sensor size. P1 is good for making large aerial survey.
Other way, which could sounds strange, i already noticed that cracks on concrete are easier to detect by night with a powerful lamp mounted on the drone. The shadows make them appearing while the drone is moving.

I've never used our P1 for cracks, or 11 feet away from the subject, but it has phenomenal resolution

Blurry implies to me either a focus problem or a low shutter speed.

I have had significant problems with focus in the past when flying mapping missions, so that would be my first guess

For mapping missions, there is a focus taken at the first point, and if it's off (as in over water), then the focus for every image in that flight will be off, and the mission wasted. To avoid that problem, we define the mission so that the first image point is over land.  Since we fly islands, if the satellite image used to define the mission is old and beach has moved, it's a wasted flight.

It's a silly problem for such a sophisticated system.

You don't mention whether you were flying a pre-defined mapping mission when the images were blurry or whether the manual focus pictures were clear.

I haven't tried lately, but they might now allow either manual focus for mapping missions or more than one focus point.

You might also run through the focus calibration sequence to see if that helps.

Hi, there. Thank you for your inquiry.
We recommend that you fly as close as possible under the condition of focusing to ensure that the photos can be well analyzed. Please note that the premise is to ensure the safety of the flight.
If there is anything else that we can help with, please let us know.
Thank you.

DJI Natalia Posted at 11-13 00:34
Hi, there. Thank you for your inquiry.
We recommend that you fly as close as possible under the condition of focusing to ensure that the photos can be well analyzed. Please note that the premise is to ensure the safety of the flight.
If there is anything else that we can help with, please let us know.

In other word, fly a smaller sensor to be able to fly closer to the object, and be able to capture default in concrete

Thank you for your answers!
FYI, the last flights were manually, taking pictures 1 foot by 1 foot , it was at 7 feet away from the surface of the span (underneath). And the results were much better.
Is it possible to take the pictures automatically every 1 or 3 seconds with automatic autofocus?
Thank you