In this review I am concentrating on general use and operation of the drone and its use for surveying. The first thing to note, as with all the Mavic 3 range of drones is their size and weight. They are compact and given the on board technology light at c950g. Whilst drones generally are extremely reliable there is the additional comfort that these drones have a lower mass than alternatives. That to me does have general safety advantages and mitigates risks when in use.
The drone was delivered on a Friday and I had the usual few "test" flights at home to familiar myself with its operation. That actually didn't that take that long as the drone is very similar to the Pro version. I do tweek some of the settings (pitch/roll/yaw) to make it slightly softer on the sticks and we all have are personal preferences.
Within 48 hours of unboxing the drone I undertook my first test survey using the Pilot 2 App. I found that easy to set up and intuitive although on this occasion I couldn't get the RTK unit functioning. That was soon resolved on the Monday morning with a call to Ben at Drone Pilot Academy, put simply it was a couple of minor changes to the settings.
Another 48 hours on I had a quarry survey to undertake in South Wales. It is a quarry I have had some involvement with in my previous job so knew the site. It is a hard rock quarry on the side of a hill with significant elevation changes from the top to bottom of the site. I took both the eBee and M3M and had set up missions for both of them. Flying it with the eBee would have been straightforward but I did want to put the M3M to the test.
The whole survey was uneventful and I carried out a cross grid smart oblique (I will cover this in another blog) survey which took about 1.5 batteries to complete. In addition I used the Terrain Follow function which allowed the drone to maintain a constant height above the ground. In setting up the drone I had been advised the keep the camera in auto mode, something I would have never have done with a Phantom, everything was manually set. The proof of using Auto is in the imagery captured and what a surprise. The quality of the imagery was excellent in particular bearing in mind that it is December. For photogrammetry there are various opinions on carrying out survey work when we have low winter sun. A minimum sun elevation is sometimes stated as 22 degrees whereas in December in the UK at best it is 17 degrees. An overcast day certainly does help as long shadows can cause issues with processing the data.
The result of the above of that with the lower light levels if a Phantom was used the shutter speed would get as low as 120th assuming you kept the ISO at 100. The slow shutter speed is clearly going to reduce image sharpness. When you then see the M3M flying at twice the speed of a Phantom you have to think that image quality will be compromised. That was the surprise, the image quality was excellent for the prevailing conditions. The auto mode handled it very well with the ISO increased to get a faster shutter speed. It is evident that the sensor on the M3M captures more light than the Phantom or M2P.
Following the first week of use I have undertkaen quite a few more surveys using both the RGB lens and the multispectral functions and all of those have gone well. Once set up the RTK function is working well, I am using a mobile phone to connect to the Trimble VRS network.
In conclusion I am very impressed with the M3M and am enjoying using it. I will follow this with a blog on comparing results at varying heights using the RGB lens and my first multispectral job.
