With a range in excess of 100m and able to measure over water, the SF11/C is the most cost effective laser altimeter for drones on the market today. Compatibility with Pixhawk and derivative flight controllers and its multiple interfaces including serial, I2C, analog and USB make the SF11/C the easiest plug-and-play solution for altitude holding, terrain following and safe landing.
The SF11/C was developed to handle the unpredictable real-world conditions that sensors face when attached to a drone. Environmental factors including vibration, wind, noise, temperature fluctuations and extreme contrasts in lighting from brilliant sunshine to pitch dark are all managed by the SF11/C, and whilst all this is going on, the SF11/C measures to rapidly changing terrain, giving stable results over wet and dry surfaces without producing false readings.
Tests conducted by the Center for Research into Ecological and Environmental Modeling at the University of St Andrews in Scotland demonstrated the abilities of the SF11/C over wetlands and open water. Their requirement for consistent results under these difficult conditions were easily met by the SF11/C, contributing to important conservation work.
An important characteristic of the SF11/C is its long measuring range. This is especially useful during changes of roll or pitch angle. Data from the IMU is used to correct for geometric effects during such maneuvers, but this only works correctly when there is valid measurement data from the laser. The long measuring range of the SF11/C makes this possible as you can see from the graph below.
The green line is the roll angle, the purple line is the barometric height referenced to sea level and the red line is the uncorrected, AGL altitude from the SF11/C. During tight turns the measured distance increases significantly but the long range capability of the SF11/C keeps the ground clearly in view.
More details about the SF11/C can be downloaded from the website. The SF11/C is manufactured by LightWare Optoelectronics (Pty) Ltd based in South Africa. LightWare has been designing and manufacturing laser altimeters for the drone market for 5 years and is committed to providing high quality products to the industry. The official distributors in the USA are Parallax and Acroname.
Special thanks go to the dev team for their contributions to the driver software and Tridge for his tireless and occasionally incendiary flight testing ;).
Comments
@Jason - so would these trigger points be totally independent values or could they be entered at equal spacing? I'm just trying to imagine the setup process - it would be tedious to type in 50 values and easy to makes mistakes.
@laser Developer yeah it was bit extreme most i have done was 50trigger points to 100m. I think 50 is more than enough.
Our average is around 20 to 30 in one flight.
@Jason - Just to clarify: For 100 different trigger altitudes, are you saying that you might need to trigger every 1.0m up to a range of 100m? I was thinking in terms of entering a number of trigger heights, but entering 100 values seems a little extreme. Am I missing something?
How many trigger points do you need?
100 would be enough 50 min
What would be the typical "on time" to activate the shutter?
as soon as the height is reached. one shot maybe 1sec?
Should the trigger take a single shot when the reading is inside a predefined window and reset once the reading is outside the window?
yes
Should the reset window be wider than the trigger window?
yes
Are there any other features that would be useful?
i am thinking some sort of wifi feature to use to iphone/ipad or notebook. carrying around a laptop is heavy.
SO our main business is "balcony shots" for high rise buildings. Say our customers want photos at 3F/ 5F then at 10F. at the moment I fly up to the required height using the laser as reference then we take a picture close to that as possible. As we found out it is possible to take one picture/ or multiple pics at one preset height. I have proved this will work for 360 panoramas quite well. But it would be nice to able to preset the heights of say 5m /10m and 15m i require then take-off and when it gets point A. takes a picture then so on.
@Jason - brilliant, thank you!
Let's talk about specs for an upgrade to the SF11/C. How many trigger points do you need? What would be the typical "on time" to activate the shutter? Should the trigger take a single shot when the reading is inside a predefined window and reset once the reading is outside the window? Should the reset window be wider than the trigger window? Are there any other features that would be useful?
@laser developer Ok something to think about then please!!
I posted my findings on a few mulirotor/uav forums today hopefully it will create some interest! any maybe give you some more customers! I hope it works!
@Jason - very cool!
It is possible to include multiple trigger points. You're the first person to ask for this but if you can find a bunch of like minded people who are willing to buy a product that has this feature built-in then we can definitely add it to our dev program.
@laser delvoper thanks very much for your help.
any chance you can upgrade the software to make it set-off more than one alarm points?
That would be a real game changer for my work. Cm accurate photos are awesome!
well I got the nerve up and tested the shutter cable wired directly to the laser at the min setting which is 1m.
ITS WORKS. i tested it on my movi gimbal outside. I stood in one spot and lift it up and down to get the shutter to work. With out editing this the result almost perfect panorama.
The real test will be when i use it on my drone at higher levels and My flying skills to set it off.
From what I can read, the remote shutter control is a "pull down to ground" switch. Inside the camera, the trigger line is pulled up to 3.3V using resistors so on a multimeter it should read 3.3V when not active and 0V when the switch is closed.
I'm a bit reluctant to give advice on this because the camera is expensive, but it looks like it is possible to wire the analog/alarm output from the SF11/C directly to the shutter control line. The SF11/C and the camera must share a common negative voltage which is one of the other lines on the shutter control plug.
On the SF11/C you will need to set the Alarm Voltage range to be 0 to 3.3V and then set the Alarm Polarity to be active low when the target gets close. The alarm level will only go back high once the target surface moves further away and this resets the shutter ready for the next trigger.
To make this circuit safer, you can add a 1k resistor in series with the alarm line between the SF11/C output and the shutter trigger input. This will limit any currents that may flow if there is some unknown protection device or other difference in the circuit inside the camera.
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