Field Notes: Turning Drone Images Into a Map

1. Why I went out

I used a local sporting field to practise a full drone mapping workflow: planning the job, flying the site,

processing the images, and seeing whether I could turn the result into something presentable. The field

was a venue for both cricket and soccer and had some interesting ground features – a synthetic cricket

pitch, worn patches due to use at common points.

2. The plan

The main focus for this mission was simply to get used to the process, in fact, to create a process, fine-

tune it, see where there were gaps and what didn’t work.

The plan was to capture clean top-down imagery for an orthophoto, then add a few oblique images and

video clips to give the site more context. I would do a manual run, flying a grid pattern and taking

photos at regular intervals. I would also use the DJI waypoint software to automatically gather data on

a grid pattern. I would also use the waypoint software for the oblique images and the video.

I wanted to use free software to process the images and chose WebODM to do this. I would create an

orthophoto, perhaps a 3D model, and a 5 – 8 page report similar to something a client might want from

such a project.

3. What actually happened

Initially I expected to use the waypoint function included with the DJI software on the Mini 5. The

software is not intended to be used for a grid capture like the one necessary for a photogrammetry

project. I did set it up and take the time to create the waypoints for a grid maneuver over the field, but it

was quite awkward. Manual capture, that is flying a grid myself and taking photos at regular intervals

through a grid pattern, worked very well and was ultimately the data I used for the final orthophoto

output.

The oblique capture that I did was run using DJI’s waypoint software. Unfortunately the settings I used

for this had the camera pointed downwards and did not produce useful photos.

There was an interaction I had with a member of the public. He believed the operation of a drone was

not permitted. I stayed calm, went with it, and ultimately said that I’d bring it in. No drama from me

and in the end it was a good experience to have and provided a valuable lesson.

4. What came out of it

The manual nadir images processed well in WebODM. The first result looked low-resolution, so I

reprocessed at higher orthophoto resolution and got a much better output.

The sporting field showing soccer goal posts and cricket pitch.

Processed orthophoto, resized from the original 354 MB output. This was generated from manually captured nadir images and resized for web publication from the original high-resolution WebODM output.

5. What I learned

Clearly the DJI Mini 5 is not intended for professional mapping use and the included software is not

appropriate for flying grid patterns automatically. Having said that, the data capture manually was more

than acceptable. The data I got was of a high quality for my intended purposes and until those purposes

change the aircraft is good enough.

One clear issue that arose was the necessity for being able to check the validity, quality, and totality of

the captured data on site. I walked away hoping the captured data was good and complete. For a first

mission it wasn’t a big issue as all the actions that surrounded the data collection was more important at

this stage. But as time goes on being able to look at the data closely is essential.

The process of capturing the data was enjoyable and did require considerable effort at first. Having

created a process and documented what works and what doesn’t, this process will get progressively

more routine as I conduct more missions. Provided the captured data is of high quality the real value,

and therefore skill, will increasingly come from the processing and interpretation stages. This is where

depth of skill and real value to potential clients exists.

6. What I’d change next time

For my next project I want to move from having done my due diligence with the JSA and set up to

capturing the data as quickly as possible. There are legitimate concerns, safety or otherwise, that need

to be addressed before setting out to fly, however this should not slow down the process. Speed of

execution is important. Establish a safe and informed mission plan, then fly the mission. Get the data

and get to the processing stage.

Having the tech to review the data on site is a priority. Taking the time to run through each image and

video will save re-flights in the future. Having a laptop ready on site is how I will proceed with future

projects.

After the interaction with the bystander I decided that having a clear script that I could use with

members of the public would be a good idea. Something memorised that I could say in similar

situations, perhaps a number or website I could direct them to if they still had doubts or questions.

7. Where this goes next

The next step is to apply the same workflow to a rural paddock, where the output can move beyond a

basic sports-field map and start becoming a simple land-condition report.

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