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  • Culver Epps

Droning (On & On)

Things have progressed over the Christmas/New Year period and I have been working on a workflow from pre-flight planning to Archicad point cloud data and beyond using a drone (UAV). This workflow uses the following software/apps;


DJI Go 4 (iOS) - Drone flight application

Litchi (iOS/Website) - Automated drone flight application

Google Earth Pro (Desktop)

Airdata UAV (Website) - Website dedicated to drone flight data analysis

Agisoft Metashape Standard (Desktop) - Photogrammetry software


I am very lucky to have friend who owns a farm very close by to where I live in the Vale of Belvoir so I can fly whenever I want (within reason of course) and get in the practice that I need before I do the PfCO (Permission for Commercial Operation) from the CAA. Flying a drone is nerve racking; 1. It is an expensive piece of kit and even though it's insured I don't really want to crash it and 2. Even though I enjoy using technology I don't quite trust it unless I can see it and with my eyesight that is not far! The fundamental of drone flying is complete trust in the technology, which is growing slowly but surely.


Pre-planning


The main reason I decided to use a DJI drone over anything else were the apps where automated flight is possible. One such app is Litchi where waypoint design and POI (points of interest) can be pre-planned, saved and reloaded when the flight is about to take place. Checking of the flight path can take place in Google Earth to check for known collision possibility!



The iOS (or Android) app takes complete control of the drone from the point of take off, flies the mission and then lands it back where it started. The image below was taken from the flight at about waypoint 5. I changed the altitude to 15m after it was clear that the wind at 30m was too rough and the drone was struggling to remain stable.


Flight


This is where I made my first mistake. The mission was to take a photo at every waypoint as this would define EXIF data required later in the process. However, in lowering the altitude it removed the stop for 5 seconds and take a photo criteria I had defined and took video instead. Now, this is OK for the test I was making but it would be no good if I wanted to locate the final point cloud in Archicad as the GPS location data is not evident in the captured frames from the video.


Building a model


The next stage, in this instance, was to capture all photos from the video to allow import into Agisoft Metashape. This model used approximately 120 images in JPG format. The software is very intuitive and has some excellent online tutorials.


According to Wikipedia photogrammetry is;


Photogrammetry is the art, science and technology of obtaining reliable information about physical objects and the environment through the process of recording, measuring and interpreting photographic images and patterns of electromagnetic radiant imagery and other phenomena


(First stage cloud and defining image locations)

(Second stage dense cloud)

(Another view of the dense cloud)


Next steps


All in all it was a successful first attempt. The next stage is get the EXIF data and import the cloud into Archicad.

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