Building a UAV for photo mapping - The Goal

Hi

My name is Paul Gregory and I read about this site in the Economist article. As I now live on a small wine and olive farm in Italy, the idea of building a UAV to produce high resolution aerial photographs of the surrounding area seems not just great fun but also very useful. I have been researching and reading a lot over the last month and as I am now ready to start my project, it seems time to share my ideas and progress. Hopefully your comments will help me avoid too many mistakes before I make them.

I have always found that a very clear goal is vital to the success of any project. My goal is:-

“To design, build and fly a UAV to produce a composite orthographic photo-map of a 2km square area at a resolution of 12cm per pixel or better”



The area where I live is very hilly with a mixed terrain of forest, arable
land, vineyards, olive trees and scattered farmhouses. To give you some idea of scale, the ridge on the horizon is about 2.5km away. The valley floor drops down by about 100m before rising up again to the ridge. There is really no flat ground around so runway takeoff is out.



There is a patch of rough ground behind the house, but this is perpendicular
to the prevailing wind direction. Given the topology, I think that a hand launched sailplane with some form of air break to given a semi-stall landing is the best option. Electric trainer aircraft with wheels are out. I also think that, within reason, the bigger the better as a larger airframe should be inherently more stable than a smaller one. Since I am learning to fly using a Multiplex EasyStar, it seemed a logical step to use the Multiplex Cularis at the basis for my UAV.



Building a UAV for phot mapping - Previous Posts

  1. The Goal
  2. Camera Selection
  3. Packing it all in

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3D Robotics
Comment by Chris Anderson on December 20, 2007 at 10:06am
Paul,

Great project, with a really well-defined goal. I think the Cularis is indeed a good choice for aerial photography (the Pict'Earth guys are using one) and I've pinged them to see if it's a good choice for an autopilot, too. One of the issues with planes with the equipment compartment in the nose, as is the case with sailplanes like the Cularis, is that you're limited in how much weight you can add without throwing off the CG (or having to add lead to the tail). But given your landing terrain, I can definitely see the argument for a belly-land foamie, and if you use a light off-the-shelf autopilot like the PicoPilot and can live with a small point-and-shoot camera like a Canon SD1000, you should be ok.
Comment by Paul Gregory on December 20, 2007 at 11:11am
Chris

Thanks for the comments. I have already started thinking about total weight and COG and how to modify the foam airframe to fit the camera and autopilot. I will cover this in a later post.
Comment by david riallant on December 20, 2007 at 2:28pm
Paul
you have set up a clear goal which is the best way to get started.
My advices considering the image processing part as you plan to create orthos are :
- fly as high as possible (and allowed) in order to get as little images as possible to process => this means having a good camera (10Mp for example)
with a canon IXUS 900 for example flying at 500 meters elevation will give you the 12 cm you want.
At 500 m elevation, you will have about 16 ha per image with a swath of about 460 m. Depending on the shape of the area and overlap (rows and lines) you can evaluate the number of images necessary.
Of course the number of MegaPix is not the only issue for quality.
As Chris says Cularis is a good choice but you may have some issues to put the gear inside properly.
I am sure that you will get the best advices on DIY Drones to set up you system.
Comment by Paul Gregory on December 21, 2007 at 9:53am
David

If I do not watch out all the work will be done for me! I have posed another entry about the camera and the elevation issues you cover here. I am not sure yet how to best organise my posts or how to make reference to comments in my other posts.

Regards

Paul

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