Aerial Mapping with multicopter

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

Hi Nathan, here is what I do. I place the camera in aperture override mode, set the focus to infinity, the ISO to 100 and the aperture to somewhere between 3 and 5.6. Take a few shots from the ground. If the shots are two bright or dark, you’ll need to adjust the ISO or the aperture. Also, keep an eye on the shutter speed as you take the test shots. You want a shutter speed above 200^th /sec most of the time. If you’re shutter speed is to slow the images will have motion blur. It’s all a balancing act. One set of settings may be great in the morning and bad in the afternoon.

My UAVs are typically moving when the photos are taken. If you have a fixed wing and can kill the motor during the image taking, that helps with quality too.

Hope that helps,

Mark

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mark sett November 4, 2013 at 5:17pm

I mark. Im a 3D architectural artist and I'm planning to do even photogrammetry for my clients. This is my parts list tell me something.:
Hexa copter cf 80cm and 20mm diameter booms
Apm 2.6 plus telemetry sonar gps
Tarot 4114 320kv and 15x5 props
Esc 40c and 2x6000 lipo
Gimbal I have no idea (2axis)
Camera d90 and tokina 12 24

I'm searching for an open source app to generate dtm. Some advice about it?
Thanks for share your experience
jeffrey miller August 2, 2013 at 11:13am

Thanks Mark. I came across this gimbal unit here: http://www.hobby-wing.com/arris-cm2000-gopro-brushless-gimbal.html. I wasn't necessarily looking for something with a gyro, just something to stabilize a downward facing camera.

I am in fact looking for the best accuracy possible. I'm a photogrammetrist with a growing interest in budget UAS that can create professional quality maps and orthophotos.
Mark Willis August 2, 2013 at 4:05am

Hi Jeffrey,

In that video I was using a Hexakopter with a gimble the was stabilized by the onboard controller. If you're looking for a servo with gyro built into it, I would get the GS-1 from here http://www.dunehaven.com/consulting.htm

I went a little overboard on the GCPs and used a TDS and DGPS for measurements. You probably don't need that level of accuracy though.

I'm doing larger areas now: https://www.youtube.com/watch?v=_kvv0092Qmg&feature=c4-overview&...

Hope the helps,

Mark
jeffrey miller August 1, 2013 at 9:03pm

Hi Mark,

Couple of questions for you:

What kind of mount did you use for your camera? Was it gyro stabilized? How did the mount you used account for times when your quadcopter was not level.

What did you use to measure the GCPs? something off the shelf?

I'm interested in doing something similar to this for my graduate thesis. Thanks for any feedback.
Mark Willis April 30, 2013 at 5:03am

Hi Nathan, here is what I do. I place the camera in aperture override mode, set the focus to infinity, the ISO to 100 and the aperture to somewhere between 3 and 5.6. Take a few shots from the ground. If the shots are two bright or dark, you’ll need to adjust the ISO or the aperture. Also, keep an eye on the shutter speed as you take the test shots. You want a shutter speed above 200^th /sec most of the time. If you’re shutter speed is to slow the images will have motion blur. It’s all a balancing act. One set of settings may be great in the morning and bad in the afternoon.

My UAVs are typically moving when the photos are taken. If you have a fixed wing and can kill the motor during the image taking, that helps with quality too.

Hope that helps,

Mark
Nathan Smith April 24, 2013 at 1:48pm

Hi Mark,

I've been trying to do something very similar with a hex that I have available, but I've been having terrible luck with our cameras. I've tried a PowerShot A3400IS and PowerShot SX200IS, but both have struggled to take images from the air (overexposed, underexposed, motion blur, lack of focus, you name it, the images have got it). What mode do you shoot images in? Also, is the platform loitering (i.e. hovering stationary) when you shoot the images, or is it in motion?

Thanks!

Nathan
Gareth Rens May 23, 2012 at 2:20pm

@Mark, Thanks buddy :) Im new to the whole photogrammetry thing. Question, im using photomodeler scanner. Are GCP neccesary and what exactly are they? Are they virtual or are they like physical calibration sheets that you put on the ground?

Also what is the best altitude to take photos from?

Thanks!
Mark Willis May 23, 2012 at 11:21am

Gareth, A Nikon CoolPix should work fine for photogrammetry. Most of my cameras have lower resolution than that.

-Mark
Gareth Rens May 23, 2012 at 9:59am

Will a 16mp Nikon coolpix be sufficient for photogrammetry? Im going to be doing volume measurements of compost stacks.
Mark Willis June 27, 2010 at 6:01am

As a part of the NASA Space Archaeology Program I'll be discussing how to produce 3D models from Multicopter Aerial Photograph (MAP), Kite Aerial Photography (KAP) and Blimp Aerial Photography (BAP) as well as discussing Structure from Motion (SfM) applications that can assist in low altitude remote sensing. The workshop is this week (June 29 to July 2, 2010) and is on the UC Berkeley campus. The workshop is already full but if anyone in the Bay Area and would like to get together for a coffee and yak about this stuff, drop me a note.

-Mark

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