3689528575?profile=originalThis is a screenshot from Ecosynth's brand new 500 by 500 meter photo acquisition method, taken at Patapsco State Park!

3689528394?profile=originalThis is Wolfgang: our newest octocopter. It flew the 500 by 500 meter mission. Wolfgang is our biggest and heaviest copter, it can carry four lipo batteries plus its payload. It can stay aloft for 30 minutes of safe flying time. The camera is the new Ecosynth standard, the Canon Powershot ELPH 520. The camera is mounted in a card case for protection and ease of attachment to the copter; it points straight down to collect photos for aerial mapping.

Wolfgang uses the frame, legs, motors, and propellers of a Mikrokopter Miko XL.  However the brain is an APM 2.5, and the ESC's are jDrones 30 amp (those Mikrokopter ESC boards are too finicky and fragile.)  The electronics are covered by a tupperware container (not the most glamorous, but it is sturdy and gets the job done.)  It carries four Venom 5000mAh 4-cell lipos.  Control is the Spektrum seven channel.  One Garmin Astro dog tracker is attached for locating the copter in an emergency situation.

3689528588?profile=originalWolfgang's planned route in Mission Planner (created by Michael Oborne). The flight path is actually 550 by 550 meters, so that the 500 by 500 meter collection area is surrounded by 25 meters of buffer area on all sides. The tracks are 50 meters apart. The copter flies at 120 meters above the ground, so that pictures taken along adjacent tracks will overlap by 50 percent at the edges. This overlap is important to provide a seamless point cloud product.  550 by 550 is an unprecedented collection size for Ecosynth.  Layed end to end, the flight is 7.8 km long, more than twice as long as out previous flight standard: 275 by 275 meters.

3689528524?profile=originalThis screenshot from Google Earth displays the actual path followed by Wolfgang while it was gathering pictures. It managed to follow its router with great precision. I estimate it deviated no more than two meters from its planned track at any given time. In addition, according to the telemetry it very rarely dipped below 119.5 meters or 120.5 meters, so the altitude was very consistent. The groundspeed reported that it flew between 7 and 9 m/s along the tracks, which is well within desirable parameters. The photo collection took 20 minutes to fly over all 12 tracks, and the entire flight took 25 minutes including takeoff and landing.

3689528660?profile=originalAn example photo from the set. Wolfgang recorded 2250 pictures in the collection area, all of which were sharp and detailed like this one. The sun was bright and unclouded, so the lighting was consistent throughout the entire flight. These favorable conditions and outstanding copter performance resulted in a very consistent and detailed point cloud. The pictures were run through Photoscan to produce this point cloud:

(View in HD and use fullscreen to gain the full effect. At least, the fullest effect that can be gained without manipulating the cloud yourself.)

Blog post cross posted from the Ecosynth blog.

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  • T3

    *with tracks spaced apart by 113 meters, not 113 tracks.

  • T3

    Thanks!  Those are actually the reasons my lab is focused on copter work: we often fly areas that have very limited space for takeoff.  Some of our collection areas are actually in deep forest where the takeoff and landing must go through a clearing in the tree canopy.  Also, form what I've gathered from the GES people in the lab, 500 by 500 plots seem to be their bread and butter.

    This summer we are evaluating a matrix of different flight variables, including reducing the side-lap to lower percentage, to help reevaluate our standard flight practices.

    Our lab's phd student will be taking this copter to Panama next week to fly 1km by 500 meter missions, with 113 spaced apart tracks flying at 200 meters up over a deeply forested island.  He's filed flight plans and everything.  I'd be glad to share the results with you guys once we have the photos.

  • Well, there are locations where it's complicated to land or take off, for example jungle area next to a road. A 500x500m area can be already sufficient for a simple evaluation, especially when you think towards construction work. The new "Arena Pernambuco" here in Brazil sits on a slab of ground around that big. I reckon that if you don't include the 3D model and decrease overlap to 20%, you may be able to cover a much larger area up to 700 perhaps.

    Do you have any numbers on those?

    I've seen a lot of areas around here that are hilly, have lots of houses and construction, telephone poles, fences, trees or only sandy/rocky areas to land on. Planning a flight there without leaving the road for a setup is pretty complicated. For such areas, if it's not too large, this solution is great and much simpler.

  • T3

    @eduardo I agree!  However, the lab I work for is only interested in using copters.

    @Magnus Thank you!  I used the on board compass, but I used spacers to elevate the APM about two inches above the power distribution board, so as to avoid electrical interference with the compass.  GPS is the LEA-6.

  • Did you use the onboard compass or external?

    What GPS?

    Really nice picture you got!

  • Stephen, 2 year ago i do the sme thing using mikrokopter.

    I think rotorcraft is not the big deal for aerial mapping.

    Today i use some flywings(2.60m wingspam) and i do 120km per flight.

    For more bigger areas i use an 3m plane that can fly 500km and i making a 2.6m gasser flywing.

    I not discourage you, but rotorcraft are only usable to very small areas.

  • Moderator
    I also have the elph520 and its giving good results & its tiny. I have single servo connected direct to the Rx channel for the rudder, (. Not used on flying wing) press left to turn on the camera , hold to the right for continuos pictures, move left to close for landing
  • Developer

    Agisoft did a really nice job here considering that repetitive trees are the weak point for these kind work. 

  • T3

    No, we have our own script for geotagging the pictures.  Yes, all 2250 pictures went in, there were about 1000 more photos taken during takeoff, landing, and the trips to and from the launch site which we discarded.  It took about 30 hours on our very high end computer.

  • Developer

    Did you used the geotag function from APM? And did you used all the 2250 pics in agisoft? How long it took to generate the point cloud?


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