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...


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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Cheers for the kind words, I did resist adding bits of ply and carbon here and there whilst building the plane for rigidity.

I was pleasantly surprised with how it flew with minimal trim adjustments. Next is to add the dummy load, and also a mini camera with OSD, so i can see how well the motor is performing. I will use the FY21AP and FY117 OSD to do this as I know it works well with this airframe with standard PID settings. I am curious to see if it cruised with less than 10amps, and id like to see what kind of length flights I can achieve with careful throttle management. 

RE: Countdown script, I will use that instead of the AP_Photos script i have been using. the AP_Photos script does have some nice additions though, like short shutter speed etc. so all you need to do is load it and run it, it sets all the params for you. Does the countdown one do that?

Wow! are you saying that I can actually have a live Photo feed (Stills) from the Canon camera to a Video TX? 

My setup:

2200mm Version Ursus

Hs81mg Servos on Ail and Elev, El Cheapo 9g Servos on Rudders

Castle Creations Pheonix 45 esc, 60 amp burst (As i happen to have one lying around)

BRC Hobbies 300w 1000v Motor 10x7 APC-E Prop - Link

5000mah 3s 11.1v Lipo for motor, 1300 mah battery for Radio and Servos

Turnigy UBEC 

Futaba 9C 35mhz & R149DP pcm rx

Sturdy Undercarriage!

First attempted flight to gain photos for some photogrammetry experimentation..... surprisingly, not a success! 

When i'm happy with the plane on manual mode i will install the APM2 to plot fixed altitude flight paths with plenty of overlap, which i am sure will give much better photos, just thought i'd try taking some pics during the test flights for fun...

The details... 

Camera: Canon Ixus 80 running the CHDK and AP_Photos Script, I'll be trying the Countdown script next as its been recommended to me.

Flight was completely manual and the altitude was probably completely wrong, I think i need to fly at 150m - 200m for optimum results according to what others have said, this was probably more like 30. 

Camera mount, with no roll or pitch stabilization, and no vibration dampening! think this needs rework! 

A nice shadow of the plane on take off...

Probably the best shot, grass isn't the most exciting thing to look at, I think the photo is still a bit blurred

The other photos were completely blurred! as shown below, I think it may have been the motor shaking the camera, as the blurriness was wobbly, not in a straight line. Not sure how i am going to dampan the camera.

I had some power system issues down to a loose prop and poor insulation on the ESC wires, causing sparks to arc across the wires, these have now been sorted, so should be able to get some better altitude on the next flight..

If anyone has any questions/thoughts on any of the above, let me know! 

Hi Blog, 

I've just come back from attempt 2 with the same camera taking more pictures, It seems it is not possible to take sharp photos without any sort of dampening or stabilization. 

Here are 2 pictures, taken 1 second apart, the first is with the motor on, the second is with the motor off... how do people normally overcome this?

Picture 1 - motor on,

Camera: Canon Powershot SD1100 is

F-Stop: f2.8

Exposure Time: 1/100 sec

ISO speed: ISO-80

Exposure Bias: 0 step

Focal Length: 6mm

Max aperture: 2.96875

Metering mode: Pattern

Picture 2 - motor off

Camera: Canon Powershot SD1100 is

Fstop: f2.8

exposure time 1/80sec

ISO Speed: ISO-80

Focal length : 6mm

Max aperture: 2.96875

If anyone has any knowledge of how to program CHDK to take sharper photos, please let me know!

hi Richard,

Exposure seems to be your problem. you must set it Always faster than 1/400. in ckhd extra photo operations check disable overrides = disable

-override shutter speed = 4

-value factor = 1/1000

- in cloudy days, ND Filter state= on

-Iso =auto

I use exactly the same camera, and don't use any fancy stabilization. In fact I just cut a hole in the wing of my flying wing to mount the camera.

I think you will pick up some vibration from the wheels and the wooden mount you made. I would make that out of foam and move it away from the wheels. The airframe is vast can't you put the camera inside?? You will will be getting a little wind buffet as well in that position, if you can't move it add something to deflect the air away from of it just a bit of card taped on should do it.

As James said you have to force the shutter speed higher. So bright days are then required.

Best of.

Hi James, Cheers for the info, that is very helpful. I have been doing some playing around with the camera taking pics out the window, but its getting dark here, so its difficult to monitor results. I have just changed those three settings as you suggested. And when i look at the meta data of the photos, it says the ISO is on ISO200, and the shutter speed is 1/250, ISO is set to Auto in the normal camera settings, but I cant seem to find an option to set the ISO to auto in the CHDK menu. 

That's plenty for me to go on, and hopefully the next set of photos will be a lot better!

Thanks for your help!

Hi Gary, cheers for the suggestions. I am definitely going to try a foam mount or at least move the camera way from the wheels. I quite like having the camera mounted on the COG as I thought if i choose to try different cameras it will save me having to move the lipo batteries around to get the right CG. 

The reason i bought this plane was the put the camera inside it, to reduce drag, but after thinking about how and where to cut the hole in the underside of the fuse, I chose just to make a mount. Having said that, If i remove the ply wheel mounts and wheels I will save about 250g weight! 

There was another reason for making the pitch roll mount, apart from stabilization. I am trying to get good enough photos to be able to create some digital elevation models, and In the guide for the photo taking recommendations, they suggest taking the pictures straight down, so thought a servo controlled mount would ensure that I can use all of the photos, as opposed to having some pics with the horizon in etc.

I think i have got the hang of the chdk enough to be able to change the settings as per James' post. Hopefully the rain will stop in the next few days, and i will be able to try it. I will connect the video link this time so i know what height i am flying at, I am going to try 150m as per dronemappers reccomendation. Have yo found an optimum height for that Camera?


Francois, just read your post, that's a nice aircraft you got there, what kind of flight times do you get? I own a Britflight h-two-o, and have done a small amount of water based flying, it is about 1m wingspan. I would like to have an aircraft capable of staying aloft with a GoPro for an hour or so. The waterproofing techniques you have listed look good, and i am definitely going to Corrosion-x the servos and make a better seal around the canopy area, flew in moderate rain today, but only used bits of duck tape to cover the servos! 

It's belting down with rain at the moment, so a Seawind may be on the cards! 

More Blurry photos:-(.

I went out again this afternoon to take some pictures, it was quite light with blue sky between the clouds. I had some mixed results. I used the following settings on the Canon CHDK Ixus 80,

CHDK Alt Menu

Disable overrides - [Disable]

Include AutoISO & Bracketi [o] (solid circle)

Override Shutter Speed - [4]

Value Factor [1/1000]

Shutterspeed enum type [Factor]

ND filter state [On] I also tried in and out, with fairly similar results

Override Subj Dist [0]

Value Factor (mm) [off]

Override ISO Value [0]

Value Factor [Off]

Clear override values@start [o] - solid circle

Enable Fast Ev Switch [  ]

Step Size (1 EV)? [ 1/3 Ev ] 

CHDK Custom Auto ISO Menu

Enable Custom Auto ISO [  ] - (No value or dot, so I guess i don't need to show those settings)

Normal Camera Settings

ISO - ISO Auto (I also Tried  ISOHigh) - they are the only 2 options

AF Frame - AiAF

Digital Zoom - Off

AF-assist Beam - On

Review - Off

Review info - Off

IS Mode - Continous

Okay - here are the pictures with Picture attributes

First picture, a bit dark, I think I had the ND Filter state On for this one

Picture 2

A bit lighter, Think the ND Filter was on Out for this one

The Mount was the same as before, therefore I guess there must be a lot of vibration coming through to the camera. I will add some foam in between the camera and the plane to give a softer mount to hopefully get rid of the burriness.

I also had more power system issue, he motor is stuttering, and running very rough, which leads me to believe there could be a problem with the Motor or ESC. Either way, I am going to replace both with some higher quality units. 

I am sure there a [plenty of nice 300w 1000kv motors that will turn a 10 x 7 nicely on 3s, as this does seem to have enough power. draw 25amps on WOT, but cruises on less.

I also bent the front nose wheel beyond repair due to a hard landing, the power stopped and the airspeed was a little low into wind, dropped like a stone! The rear aluminium struts also bent badly. 

Back to the drawing board!! - thoughts?

Good morning Richard, 

the factor 4 * 1/1000 gives you shutter speed 1/250 which is a bit low, but i didnt new your area solar radiation also i didnt gave attention to your camera model (80is), ND filter doesnt make any difference fo 80's.  

So give it a try with factor 2 (speed 1/500) or 3 (speed 1/330).

the usage its better explained here: CHDK Shutter Speed Overrides Explained 

The best way to check the camera-mount-vibration-motor combination, is to make a flight and record the highest quality video possible and then interpret the video to see what's the weakest link. ie check image quality when motor is on or off, when your are full throtle, when you glide-try to listen for air-dynamic noise etc

the CG camera is convenient but its very close to your motor.

check my first test with my 100is video: 

Hi James, 

Thanks for being so helpful! I would be a bit lost without some of the valuable information you have shared above! 

I will hopefully give it a try tonight with the above settings if the rain stops, I have also read the link above regarding the CHDK shutter-speeds, I am beginning to understand what a shutter speed and what an ISO is!

I will try a video first, and note whether the video is blurry when the motor is on. I have just fitted a new motor, the old motor was stuttering. and I think creating some torque roll and unwanted vibration. The new motor seems much smoother, I do need to repair the undercarriage as I had a bit of a hard landing yesterday, better than bent cracked foam though! 

I have had a look at your first video with the 100is. It looks very sharp indeed. I have a 120 is coming. Maybe that will be better than the 80 and give a better ground resolution if i get the vibration issues sorted. 

I have tried setting a 1/4000th shutter speed, but the camera seems to only take a maximum of 1/1500th. 

RE: ISO, I have set the ISO to auto, but have just discovered that i can set the ISO manually, is it best ot manually set the ISO? I have also set the focus to infinity. 

I have a good feeling about the next flight... fingers crossed! 

Thanks again :-)

your welcome!!

I have tried setting a 1/4000th shutter speed, but the camera seems to only take a maximum of 1/1500th. 

Men! thats near sun exposure!! I think the optimum for 80is is 1/400 and still will be darky.. so try 2 or 3 factor with 1/1000 (i think 3 its the closest to 1/400) 

from the factory camera settings set iso to auto, canons have very fast and accurate iso selection. 

And of course infinity zoom, (sorry i forgot that) 

If you find out it works, then you can enable super-fine quality from ckhd menu. 

i tested this settings without foam dampening, straight from my gimbal , in airspeeds speeds: 20kph up to  62kph @ 100m & 200m Alt.   and i had 80% usable photos, when i closed the motor, photos was 100% crystal clear! 

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

Good luck!! 

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