Hello all, I've been toying around with the MikroKopter Hexakopter as a tool for aerial mapping and photogrammetry. After a few weeks of learning the ins and outs of the system, I finally had some time on the weekend to test the system for mapping.
In short, we placed Ground Control Points (GCPs) around a man-made ponding area at roughly ten meter intervals (~40 x 30 m in total area). The GCPs were shot in with a deferentially-corrected GPS (~0.1 m horizontal and ~0.2m vertical resolution) and with a Total Data Station (>0.03m vertical and horizontal resolution). We then flew the Hexakopter at 40m above the ground surface in an east-west grid pattern with a photograph being taken straight down every 10 m or so. The camera used was an off the self Canon A540.
The photographs were processed to remove most distortion and dropped into a photogrammetry program. A 0.05 m resolution DEM and 0.02 m photomosaic was created from 22 images. It took about two hours to collect the photographs, and shoot in the GCPs with both the DGPS and TDS. Processing of the imagery was nearly flawless and took about two hours as well. This time can probably be reduced to an hour or less.
Compared to doing this same process with a kite or blimp, I am very impressed with the Mikrokopter (and multi-copters in general) as a platform for high resolution, low altitude mapping. Let me know what you think.
Over the next few weeks, I'll be testing the same process in at a couple of archaeological sites in the southwestern US. I'll share some of those results when they are complete.
Can't wait to play with the truly opensource Ardupilot!
-Mark
Comments
http://70.114.149.18/~mwillis/Hexakopter_3D_Mapping.kmz (~13.2 Mb)
I'll be flying at a large archaeological site that is 1.1 by .4 km in size later this summer. That should really test the boundaries of the machine and technique. This should give the best evaluation of the process using the hexakopter. I've also got a Hawkeye setup with ArduPilot. Hoping to see how it does also.
Using the hexakopter there really aren't any bottlenecks (other than the learning curve of LPS which is very steep) in the post-flying workflow. The largest bottle neck is the flight time (about 18 minutes) and self-imposed limitations of the Hexakopter (maximum flight radius is 254 m).
If you compare the time (and cost) it would take to collect the same sort of data with LIDAR, from a manned aircraft, or via traditional ground survey, it's very and fast.
The post processing workflow is fairly simple:
Download images from camera.
Undistort the images in MatLab.
Download telemetry data from UAV
Enter telemetry data associated with each photograph in Leica Photogrammetry Suite (LPS).
Download DGPS coordinates for Ground Control Points (GPCs) and enter into LPS. (This is mainly to check for accuracies)
In LPS, associate the GCPs coordinates with the actual targets in the photos.
Tell LPS to generate a DEM and photomosaic
Voila! Nice DEM and Imagery.
Those are the basic steps and there can be pitfalls that cause problems along the workflow. That's essentially it tho.
By the way, the resolution of the DEM and imagery in the animation could have been much higher. I just opted for that resolution to speed up my rendering software.
Here is a Google Earth KMZ file with the full resolution data:
http://70.114.149.18/~mwillis/Hexakopter_3D_Mapping.kmz (~13.2 Mb)
My bandwidth is limited and the server is a little slow so please be patient.
-Mark
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