I've got two cameras, a Canon SX260HS and a Sony Nex N.
I would like to use one of them in my next multirotor and I'm looking for a gimbal.
I want to use the multirotor for GIS purposes, so the gimbal must be able to be pointed straight to the ground (orthographic pictures).
I don't mind to be able to move the gimbal during my flight, I just want the camera to be stabilized without any vibration.
Do you have any idea which gimbal could be the best one regarding my needs ?
By the way, could someone explain me the differences between :
* Brushless Gimbals
* 2 axis gimbal
* 3 axis gimbal
Brushless Gimbals - Uses brushless motors to keep the sensor (camera) level and on target with the subject. Brushless require less maintenance then brush motors and last longer.
2 axis gimbal - The sensor will rotate around two axis. If you where to use this on a aerial platform (ie multirotor), the gimbal would keep a camera level by compensating the aerial platform's roll and pitch.
3 axis gimbal - Just like a two axis it would compensate for the roll and pitch, but also for the yaw.
Thank you for the explanations about the gimbal.
I understand now the differences between them.
Do you know a good gimbal for a Nex5 or SX260hs that could be oriented to the ground ?
Im new to this too and I dont have any experience with them. As of now Im using a fixed wing (bixler 2) and 3dr Y6 without a gimbal and get pretty good results. I also dont have to worry about the extra weight and I get longer flight times. I am using foam in between the camera and platform to damping the vibrations.
If your not using it for video, you may want to consider a servo driven gimbal. It doesnt have the resolution of a brushless gimbal but it would work well for capturing images. [I would like to hear anyone's opinion on this]
Pointing straight down is called the nadir view. I use cameras on multi rotors too but until now never bothered to stabilise the pictures. The obliqueness in theory impacts the precision, but there are many other factors to consider that also impact precision. Similar to distortion, obliqueness can be compensated in the final images and professional post-processing softwares derive the camera attitude through a set of algorithms.
The biggest concern for having a gimbal is when you have a shaky platform, for example a foamie with slow servos in strong winds. Then the gimbal would help significantly to counter the camera movement, which allows you to reduce overlap. So the direct concern for using gimbals is to increase efficiency (less overlap) and to reduce the probability of useless images.
Personally... I'd give it a shot with a directly mounted camera and see what the results are before investing in a gimbal. If you have a lot of vibration, then you can always add a couple of dampeners with a secondary mounting plate beneath the actual one. Vibrations are going to affect you in low-light conditions, so those need to be controlled.
A reference document for GIS mapping, not sure if it's still available on the site:
Thanks for the information and the explanation about the nadir.
You are right, I will try first without a gimbal and see how it works !
You mentioned that you have some multi rotors as well for taking aerial pictures.
Do you use one almost RTF like the ones from 3DR or did you built your own ?
The book you told me about is still available and can be downloaded here :
@Flying Buddha, why did you say "If your not using it for video, you may want to consider a servo driven gimbal" ? Why servo driven are not good for this ?
Thanks guys for your help !
I start to understand a bit better.
I built my own which can stay in the air for >30 minutes.
The advantage of brushless over servos is the very low lag in the response time (servos take more time to move), higher resolution so no jittering like servos sometimes do and not subject (afaik) to voltage ripples. Also, no gears and less momentum.
It does force you to hang the device in the center of all axises to minimize any constant force you may have, because the brushless gimbal has low torque.
For servos that isn't a prerequisite, but servos will not be able to move as fast as brushless gimbals do.
@Arnaud A brushless gimbal will give higher resolution in movement which is why a video with a brushless gimbal will look smooth as moves to compensate for the aerial platform's movement. If your taking still photos, it seems as if one could get by with using servos (cheaper in price). You dont need the "smooth" movement, it just needs to be nadir.
Ive read that book and the authors mention there thoughts on the use of a gimbal for the camera and I think they had alluded that it wasnt effective as they thought it would be. As Gerard_Toonstra ponted out there is software for correcting the obliquiness. Weight plays a big part in these things, so anything you can do to remove unneeded weight helps
From my experience in the last 6 months, I have not used an autopilot (ie APM) and its pretty easy to keep a plane on track and level. My worst (off nadir) images are when Im in a turn, I bank the plane really steep to maintain my next run. I use rudder to make small corrections. I have flown a "wing" design and find those images a more susceptible (very minor compared to my bixler) to photos being rotated do to yaw.
I just started experimenting with a Y6 with APM and hopfully I will have good data soon.
Thank you both for this interesting discussion !
I will do a few tests without a gimbal to see how it works.
Have a good day.
I am using the Canon 260 on a 2 axis gimbal and am getting very good results.
The main drawback on the camera is the retractable lens.
In my early tests, I lost a Canon A2500 to grit that was blown into the lens retract mechanism. 2 flights was enough to kill the camera.
To combat the problem I am using a 2 fold approach. the first is a 5' x 5' carpet to use as my takeoff/landing pad. The second is lens protection using a 52mm UV Filter attached to a sponge with a hole cut for the lens.I have had many successful flights with no camera damage. While developing the lens protection, my first prototype protected a test camera for a 5 minute hover, 3 feet over a sandy gravel road.
Thank you, what gimbal are you using? or where did you get it?
Currently I am using a 2-axis homemade servo based gimbal. I am in the process of building a HEX for aerial photography and intend on using a 3 axis gimbal along these lines http://www.uavobjects.com/product/asp-3-axis-nex-gh5-gimbal-alexmos.... For my purposes, a 2 Axis is all that is needed, but the third axis gives me a bit more flexability.
In the 8 years I have been doing this, the biggest issue is bluring of your photos. This comes from many directions, the 2 major ones are unwanted vibrations and motion of the aircraft. The vibration issue can be mitigated with balancing of the motors and propellers, which is a cake walk when compared with getting a 600 size helicopter balanced. Also the "rubber ball" vibration dampers are fantastic for mitigation of vibration. Bluring of the photos is much more difficult to mitigate, here are my steps.
1. set the "film speed" of the camera to 800 or above. This will give you faster shutter speeds.
2. use fast motors in the gimbals, In my servo gimbal, I am using using high speed futaba servos from one of my old helicopters.
3. Fly your photo mission at least 2 times. I currently fly 3 missions with the first 2 being the same and the third being perpendicular to the first mission. Be willing to review each photo to remove the bad ones.
4. Set up your mission to do any turning outside of your photo area.
5. Altitude/Flight speed. Adjust the speed of the flight with the altitude you fly at. Lower altitude = Lower Flight speed
6. Be reasonable in your expectations for the area you want to survey, you need to plan for non mission flight time (take off/landing) plus reserve time.
I fly both an Airplane and Quad for aerial photography, what I use depends on the size of the area I want to photograph..
First and foremost LEARN HOW TO FLY YOUR EQUIPMENT WITH OUT HELP FROM THE APM. Stabilize mode for a 'copter, No APM for an airplane.
I'm also trying to select a gimbal but I'm using mine for research so my camera needs to face straight down in the nadir view you mentioned. Can I purchase a 2 axis brushless gimbal and then just modify mounting so that it points down or do I need to get the 3 axis gimbal?