Over the past year I have undertake more large UAV surveys. These vary considerably and include farms, piplines, greenfield sites and ongoing developments. By their very nature and scale these projects can take some planning and I have found a good workflow really helps. By way of background I fly DJI Inspire V2, use ArcMap, ArcGIS Online, ArcExplorer and Drone Deploy. I have tried Arc to Map but haven't adopted it, two reasons, functionality and price.

When a large job is proposed the first task is to check that it can be carried out and therefore not close to airfields, prisions or other restricted areas. Ancillary to that consideration needs to be given to flying near/within congested areas and in particular noting the proximity of major trnasport corridors. This will be part and parcel of the workflow of all licenced operators.

The next part is planning the flights needed to capture the data and this is where ArcGIS comes in. Firstly ArcGIS is used to identify the actual site to be flown and the congested areas etc can all be identifed. When you are dealing with a large site, say 100 acres plus the site will need to broken down into a number of flights. For example the property I flew yesterday was split into 10 and covered over 250 acres. The criteria I use is twofold (1) an area such that it is all with 500m and (2) within a suitable flight duration.

For general flight planning I generally use about 450m as a maximum distance to allow a bit of leeway and aim for maximum flight times of 11 minutes. Whilst an Inspire with a TB48 battery in light airs will fly for upto 15 minutes (and a little more if battery levels allowed to drop a bit more), 11 minutes allows a safety factor. You have to take into account a minute maybe more for the UAV to climb to the required height and to get to the the first waypoint and not forgetting that at the end of the flight it could have 450m to fly back to the starting point and land. If wind speeds are higher than expected this will bite into flight times. Depending on your clients requirements and the outputs you also need to take into account the height you intend to fly at and overlap for imagery capture. These can have a significant bearing on flight times.

With these parameters in mind the flights are planned using ArcGIS. I create polygons for each flight and in parallel set these out in Drone Deploy. By doing this I can then check flight times for the given flight height and overlap. I prefer this method that doing the design fully in ArcMap and them using then importing the shapefile into Drone Deploy as it saves time. An additional factor in planning the flights is that I can also determine the best location for Ground Control Points where they are required. I am able to place them in ArcGIS so that they are visible from more than one flight which helps improve map accuracy.

Once I have flight planned I also add take off/landing points. This may seem overkill but there is a benefit. If you have deisgned flights that are close to the 500m maximum flight distance the margin for error in using a take off point is small. Move to 510m then Drone Deploy will not initiate. 

Having planned the flights, the take off locations and GCP's (if required) I then tranfser this data to ArcGIS Online. From here I create a Web Map. This is the important part of the workflow as this allows me to have the full details of the flights accesible on my iPhone using ArcExplorer. This part of the workflopw saves significant time in the field. When I arrive on site I already have access to where the GCP's need to be placed and I simpe use Arc Explorer to take me to that location. The same applies to the take off points. This allows flights to be conducted efficiently and saves times over the course of the survey.

I have also found a further benefit and that is when you collect up your GCP's. Again ArcExplorer can take you back to the exact point. It is remarkable how hard it is to see a GCP in a grass field!

If you look closely at the picture you will see a GCP (white cross) to the right side. This was only 10m metres away. I should add that were possible I do use line marker for GCP's. On two recent jobs for various reasosn I was unable to use line marker. Where you can do so as it does save a lot of time.

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