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!

Tags: APM2, Canon, FY21AP, GIS, Gimbal, Photogrammetry, Ursus, chdk

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Suggestions for Waterproofing the plane/groundstation from rain. I'm looking for any advice on waterproofing this. As the weather in the UK has been shocking for 2 weeks! And i want to maiden this thing!!

I've done a fair amount of APM flying in the the rain here in Oregon, and the solution for me was to purchase a NEMA rated enclosure from Digikey (about $18), and mount the xBee, video receiver, USB video capture, and a USB hub inside it. I cut a hole in the side of the enclosure and added a panel mount USB-B jack, and connected an 1800mAh lipo battery and 5V step down voltage regulator to the HUB. I drilled two holes on the top of the box for the xBee RPSMA and a 5 inch SMA extension to attach to the video receiver. With this setup I simply run a 10 foot USB cable to my laptop, out of the rain. The USB jack isn't weatherized, but I haven't had any problems in light rain- yet. I looked into some sort of weatherized 4 pin connector, and most were about $40. If you wanted better waterproofing you could drill a large enough hole in the enclosure to run a USB cable into it and seal the hole with some Sugru or silicone.

Hi Seth, this is exactly the kind of information i was after, I have read through the various ways you have waterproofed, and it makes perfect sense. I am looking at getting one of those cases as well. I t has rained here everyday for over 2 weeks! 

I see you are using an easystar type airframe, have you done any waterproofing to the components, servos, battery, servo leads?

Rich

Yes, liberal use of 3M tape around the forward hatch and partial covering of the top part of the engine cooling inlet. It's worked really well- I've inadvertently flown through some heavy rain and strong winds!

We currently have much of the Same weather in the UK! and its forecast rain for the next 7 days! Best get down to the 3M tape shop! 

That looks so awesome. I'm new to this and I'm not sure of the exact term of 'weatherized,' or if the USB-B plug is actually exposed ( I doubt you did that), but my first impressions are that it is. I get plugs like these for almost all my electronics as I try to avoid corrosion/dust, so hopefully if your USB-B plug is exposed this would be helpful. USB-B Cap

In terms of your ground station case, do you find heat build-up to be an issue?

Waterproofing the plane: This is probably overkill for your needs, but my ArduPlane is based on a Seawind EP and I fly off water. After my first swamping I went to extremes to waterproof the electronics. The Spektrum receivers, APM boards, GPS and telemetry radio are housed inside the hermetically sealed canopy that came with the model. To retain barometric altimeter functionality, the case is vented to the outside atmosphere via a tap in the static line that feeds the pressure differential sensor.  
 
I use Plastidip on all small parts that are outside this container. The ESC, servos and pressure differential chip are all protected this way. I do not waterproof the battery or servo connectors, but I do keep them above the floor of the fuselage in case of water infiltration. As you can see from the beat up paint on the plane, I also use tape around seams, but water can still get in, typically because of a lousy landing or in choppy water. Brushless motor bearings only need the occasional oiling to keep them healthy.
 
Here are a couple videos of different techniques I incorporated for the servos:

Servo waterproofing1

Servo waterproofing2

Since your are mostly dealing with high humidity, you can probably get away with just using CorrosionX, Corrosion Block or some other conformal coating for your electronics. NB I would avoid getting that stuff inside the pressure sensor on the APM. 

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! 

Thanks Richard. The Seawind EP has its quirks, but it flies well.
 
One note: I haven't used CorrosionX (couldn't find any) but I have read that you should only use it on the circuit board of your servos. Apparently it can foul the servo motor. Also, it isn't foam safe, so treated components should be dried prior to reinstalling in a foam plane.
 
To answer your question, with the stock Rimfire 400 motor, endurance is reasonable considering how heavy I fly the model. Last season, with all the APM gear and a big 2200mAh battery, gross weight topped out at 32oz/908g. Typical Air Time with aggressive flying is 15 minutes. The longest Air Time was 21 minutes of mixed flying, including circuits and multiple take offs and landings while calibrating the airspeed sensor and testing PIDs. Recharge was 1966mAh, or about 100mAh per minute of Air Time. The battery was plugged in for a total of 40 minutes on that flight, which is typical because of those quirks I mentioned.  

Specifically, the canopy that houses the majority of the electronics acts like a greenhouse. Combined with my APM v1.4 y-gyro being thermally unstable, the result is that large rapid temperature changes cause the AHRS to tumble. It took me 6 months to get my hands on a set of telemetry radios before I could pin down the exact cause of why the plane would "depart controlled flight" when switching out of manual into any of the auto modes. All part of the learning curve. As a workaround I leave the powered model sitting in the sun for 5 or 10 minutes to make sure the DCM has a stable earth plane solution prior to flight. It eats into the Air Time endurance, but the alternative isn't pretty.
 
I'm working on modifications to increase the endurance and reduce wing loading. Like you I plan on doing aerial photography which means carrying camera gear, and the stock motor and wing are not up to the job. The picture in my previous post is of the plane while I was doing the rough installation of more powerful CR28M contra rotating twin engines. I am also building a bigger wing with flaps to slow the beast down. I plan on testing this configuration on the Victoria Day long weekend at the end of May. I'm aiming for 30 minutes of Air Time.

IMU Stabilized gimbal for Vertical photos for GIS and Photogrammetry 

As part of the project I will need to take pictures as vertically as possible. So i have made a plywood camera gimbal, There is a video of it in operation here. I will be using the FY21AP stabilization unit for Pitch Roll stabilization of the gimbal.

I am aware that APM2 does have this facility, but I have tried to download GIT, Arduino, CYGWIN etc. but don't understand the instructions. When it is built into the Arduplane code. I will remove the FY unit, and use the APM2 instead.

On another note, does anyone know if it would be okay to mount the APM2 30cm forward to the COG?

Hi Richard, 

I told you the code isnt ready yet for planes, its a pitty to use a nice stand alone device just for stabilizing. great job though with the gimbal!! 

Some advices that you will find handy: 

-becarefull with the gimbal clearance, in a "hot" touchdown your camera will take the impact

- Dont overload it with mah.. its just adding weight, You will have more flight times with 2 independent 3s 5000 flights than 1 flight with 2 3s 5000 bateries in parallel.

- we have about the same aircraft, 2.7kg its the upper edge for suffiecient wing loading, if you add APM, telemetry, covering and Canon you will pass 2.9kg, i would suggest below 2,3-2,4 kg for maiden flight.

-check out the countdown intervalometer, i dont know why, but it takes less batt and you can define the number of shots, as for the settings, go to extra photo parametres- I used shutter speed overrides : factor = 4 multiplier= 1/1000. the pictures were perfect with no stabilization and cruise speed 45 kph 

-Again becarefull with the weight, dont let FPV setups up to 4kg foul you, having a camera under the belly with a lots of drag and high wing loading will result in a speedy- stalling aircraft.

keep up, we are waiting for more photos!! 

Hi James, Thanks for the advice, Regarding the APM Camera code, I thought it was available for APM 2.0 but needed a tweak to the code by checking it out from GIT, and Using Cygwin and Arduino to get the AP_Camera Branch and load it onto the board. I was trying to follow these instructions

The Gimbal that is on the Aircraft is not the Gimbal i will be using, that is one I made to sling under the high wing on a skywalker, It has more motion than i need, I am making a slimline one which only has about 20 degrees pitch and 20 degrees roll. I stuck it under the Ursus with duck tape just to test the pitch and roll stabilization out on the FY21AP. It seems to work pretty good :-)

I never thought about doing two flights each with 5000mah, as opposed to a single long one. I guess it makes sense to do that, I am a fan of keeping things light (not that you'd think it by the amount of wood ive used on this thing!)

I have weighed everything, And with the 2 large batts, camera etc, it comes in at 2.5x KG, excl Undercarriage. I'll take your advice and ensure to maiden under ~2.3kg

I have been playing with different interval scripts. I am trying to get the screen to not show a preview of the image to save battery, but i haven't found a setting for this, All i have found is how to reduce the preview time down to 10 seconds, I haven't tried the countdown one, Is this the one you are referring to?

I will ensure to get plenty of airspeed before rotating on the maiden, I normally maiden aircraft by hand launching them, but this one will be rolling! Exciting stuff

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