First APM2 Build for Aerial Photography to create DEM,DSM for GIS purposes - Ursus Airframe

Hi Forum, 

Some pictures to start... 

Thought some of you may be interested in this build as I intend to build an aircraft capable of 1 hour flights to map large areas in order to Create some Digital Elevation models for GIS mapping purposes. Initially i will be doing this for experimental purposes. I know there are a lot of rules and regulations in around commercial photography etc. 

I will be focusing on the following

  • Best Airframe for the job, including some brief build information
  • Suitable Cameras for the project. (Canon Point and Shoot cameras using CHDK)
  • Camera Stabilization - already made a basic pan/tilt gimbal for my Skywalker using the FY21AP
  • Ardupilot APM2 Learning with Trial and Error
  • Software to create the Digital Elevation models.

I know this is a highly specialized area, but i do have some of the above from asking various people on here (initially posted about this in my blog area, but that was wrong place, so posting here...)

Right where to start...

Airframe

I have selected the Ursus Airframe for this build as it seems to have a large wing and space for enough batteries to give slow, stable flight for up to an hour or more in some cases. It has been talked about on here before

Some Stats...

Wingspan: 2200mm

Material: EPP and wood

I'll try and post more pictures than words.. .as they are more interesting to look at... 

Day 1

Airframe arrived, fuselage part assembled,

Day 2

Wooden spas glued into wings, Glass rods glued into tail booms

Day 3

Fuselage glued together, with, wooden wing joiners glued into place

Day 4

Wings joined, APM arrived, sticker stuck to horizontal stab.

Day 14

After a few weeks of tinkering, my APM2 has arrived, And with much help from Chris and Michael I have managed to get HIL mode running pretty well in Xplane 10. I have been familiarising myself with the MissionPlanner as much as possible. Learning how the PID settings work.

Servos implemented, Undercarriage on.

I have also been playing with the Canon CHDK (Canon Hack Development Kit) on an ixus 80 and Intervalometer. Which is how i will be taking the photos from the plane, I wanted to see how long it can take pics for before the battery dies, I took pictures every 120seconds, and it took 81. Review was selected though after each picture, And i will be taking pics quicker than that. I created a time lapse from the window. Not that interesting, but its all part of the learning curve.

Day 23

I have upgraded the nose wheel undercarriage to a more robust strut with steering as well. This should give plenty of ground clearance for the Camera Gimbal

Testing the placement of the electronics, need to decide where to put the APM2, R149DP Futaba RX and the Camera IMU. Plenty of room in here for 2 x 5000 3s lipos! AUW is currently 2.7kg!

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I think oblique shots will shortly become the shots of choice, you get more elevation data out of them.

@James, Cheers for the info, I have had a play around with those settings, and on 1/400 the camera still seems to blur, maybe im being a bit voilent with the camera whilst taking test shots. I had planned to go out tonight and give the plane a fly with the camera on those settings, but it was a tad windy (37mph!).... I flew the plane anyway, but didnt bother with the camera! The flight is quite interesting! 

Fingers crossed for the weekend! I did however try some 1/1500 shots on 400ISO with fairly good results, i'll be taking a video with the camera to eliminate the motion blur/vibration issues next.. :-)

Better Aerial Photo results & Photosynth

Update - Tried the recommended settings on the is80 camera.

  • 1/500 shutter speed
  • Auto ISO Auto
  • ND Filter to out
  • count down script

It was a fairly sunny afternoon so i think that helped... the low altitude photos came out fairly blurred, but as the altitude increased, and turned off the motor, the photos came out quite clear, I still need to sort out the mount, as there is definitely too much vibration causing blurry photos, regardless of altitude.

I uploaded the non-blurry pictures to microsoft photosynth, it did a fairly good job (91% synthy!) of stitching them together.. Its quite interesting, and can be found here

The better pictures... the camera selected ISO-80 for this one

Next Steps:-

  • Make an internal roll/pitch Dampened servo controlled mount to ensure vertical photos every time
  • Making the plane semi-water-proof, just in case it lands in water - as i fly close to water most of the time.
  • Add the APM2 to this airframe and tune the PIDS

Thanks to everyone who has helped me get this far! 

Hi James, I have posted my latest results below.... they are much better :-).

Plz, i have questions too, did you find any way to engage ckhd from bootable card? its a b...h unmounting and mounting the camera everytime

I have not found a way to do this with the Ixus 80. however there is a way to do it with the newer cameras so it automatically loads CHDK on boot. I have an IXUS 120is in the post that i picked up cheap from ebay, I think that camera has the capability to boot CHDK every time. I will let yo uknow if i get it to work, 

R

Wow!!you are Very very good pilot!! Airfframe also conpenshated the wind, while kept nice penatration-beside the huge dihedral.
Iam glad you finally set up your cam, very good photos& synth. Everything now points motor vibes..

Iwould suggest. Make a hole for the lense & a good dampened case for the cam inside. Until the camera code release, you will have less drag, weight, vibe and setup issues. Yesterday i removed my inside gimbal because it costed me 110gr and mounting delay for no reason

Cheers James, I think I need a more powerful motor (maybe ~600W!) if I am going to fly the plane in more than 40mph wind, as it was flying backwards!

As i didn't have much time tonight, and the conditions look favorable for tomorrow, I have quickly removed the camera plywood enclosure from its previous location, and added two 4mm strips of foam tape, and velcro to the mount, which should hopefully dampen the motor vibration,

I will be trying again tomorrow evening, if this works, I will then do what you suggested, and move the camera inside the airframe, I would like to build a lightweight easily accessible internal gimbal. 

I may get a CAD program and design the pitch/roll internal gimbal. Normally i get straight in and just start cutting wood, but for something fairly technical like this, i would like to draw it out first.

I'll post tomorrow results if they are any good!

I am going to try to record the altitude and flight tomorrow, so i can see what height I am taking the photos at, do you know if I can simply power up the APM2 (not connected ot any surfaces yet) and will it record the flight onto the card for me to view later on Google earth?

Hi Forum - 

I am a step further tonight - I have stitched together 180 aerial photos with microsoft ICE - to create this Aerial map .. the original image is extremely high resolution. I have considerably downsized it in order to upload it to the internet...

The foam tape on the mount worked okay, but still blurred 20% of the images.

Also, for some reason, some of the images have been stitched a bit strange, eg. the road at the top of the picture, i guess i need to orthrecitfy, or at least shoot straight down to ensure this doesnt happen......thoughts?

The weather has been so nice, I havent had time to make any improvements to the camera mount, or fix the undercarriage, which is totally bent after a few helicopter landings on the cliff tops, I stand by my theory though, the undercarriage breaks, stopping the plane from breaking! 

I have ordered a nice rear undercarriage set made of Carbon fiber, and the nose wheel should be easily fixable...

So instead I went to my local cliff tops and took around 500 aerial photos - of which circa 250 were usable, I let ICE do the stitching, the ortho errors are still there, as is the blurriness in some pictures. Will be working on the Roll pitch gimbal as soon as we get some bad weather and its not flyable! 

I am quite happy with the results, a bit more interesting than green fields!

Well done Richard! really ffw progress,

Microsoft ICE, has a mind of its own  i think,  try using different camera motion settings for stitching, also play with the orientation, some give better results and less oblique (hope i say that correct).  I dont exactly understand how it works, so for my job, i georeference every image separately ! and then i make the mosaic.

As for the undercarriage: 

Your airframes belly is 0,07Sq M,  If you wrap it with 2 layers extra strong 270gr/sqm carbon fibre sheet and  675gr/sqm industrial resin, your belly will be almost bullet proof, for just 85,05gr!!  if you find lighter and more robust and less drag solution, then keep the undercarriages. My A/C is still mirror like  after 50 belly landings in various terrains.

You can even wrap the belly with packing tape and then make the carbon belly, so it wouldn't be permanent. 

What do you thing?

Oh, i forgot to give you my canons roll base plans , its just for roll, but its tailored for a canon and a 10cm payload width and a hitec 422hb servo with the hitec-lynxmotion timing pulley adapter. Print them in actual size from pdf to standard A4 size paper and tick-choose paper size from source. 

Attachments:

Hi James, cheers 

I have tried using planar 1, planar 2, planar 3, rotation, in ICE, planar 1 seems to give the best results, and Automatic seems to select rotational, which doesn't work at all!  

Cheers for sending the drawings, I think I may try and build something similar, I was going to use straight forward push rods though, as opposed to a belt, I am finding it difficult to source a belt, but the Hitec cogs seem quite easy to find. 

MAy i ask, what do you mean by the following?

'georeference every image separately' 

I dont have a GPS on the camera, I do have an iphone though so I may be able ot make some GCPs?

Cheers

" I have tried using planar 1, planar 2, planar 3, rotation, in ICE, planar 1 seems to give the best results, and Automatic seems to select rotational, which doesn't work at all! "

Same for me, for auto. 

You can find the hole set of belts, servos here

To your question:

I give to every single shot (i like) spatial information, from ground control points i gathered on field, or on known points from a basemap (google earth, cadastral wms etc), like trees, building corners, roads and so on. So i know the exact location, rotation and size of my  photos overlayed on the globe.  Once i georeference-rectify the best off them, i stich them using my GIS software, providing to the algorithm the elevation model of the area, in order to "orthorectify" the hole area.

You dont need on cam GPS, you can attach X,Y cords into exif data, using Mission Planner, i really hope i explained it right.

You could download and try the demo version of Autopano. It seems to auto stitch pics together quite nicely.

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