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
Thank you...that will be my way..awaiting next batch...
@Emin - no problem, ask away ;)
Serial port connections are much less sensitive to noise than analog connections.
It is possible to use both serial ports at the same time for different peripheral devices. The Pixhawk treats serial 4 as a different device from serial 5 so you can connect the GPS onto serial 5 at the same time as the SF11/C on serial 4 (or the other way around).
So,connecting to serial i wilI have no problem with electrical noise? I know its not your task to answer this,but is it possible to connect SF11 in Serial 4/5 port together with second gps?according to specification of Pixhawk
SERIAL 4/5 port – due to space constraints two ports are on one connector.
@Emin - we've had a small challenge confirming operation in all modes with all the latest versions of the code. It looks like there is an issue with I2C in the latest release of AC but both serial and analog work fine.
The only limitation with the analog interface is that when using the SF11/C for high altitude measurements you need to take into account that electrical noise in the aircraft can show up on the analog signal, especially if there is ground loop interference. High altitude settings mean that the analog resolution is very high so even a small amount of noise can be seen on the distance reading.
In contrast, when the settings are restricted to a lower altitude, the noise shows up as a smaller distance error so it is less of a problem. As a rule of thumb, the best way to use the analog interface is to set the scale to the lowest altitude that you can get away with.
Hello...i still didn't get what is the best way to connect SF11....serial(serial4/5(no second GPS or telemetry2 port(no OSD)?)....i2c(dont like this sharing with Compass..)...my favorite would be analog (ADC 3.3V),is there some problems with Analog?
@Pmarche - Great question :). The laser doesn't penetrate the water more than a few inches so you are unlikely to get any false altitude readings from the surface. Instead, the most common limitation is that the signal gets absorbed or reflected away resulting in a "lost signal" condition. To overcome this you need to have a strong outgoing laser signal and a very sensitive detector to improve the number of valid returns. Then in addition, you need special software that can make decisions based on a sparse data set in order to provide reliable altitude results.
@Guy - In the USA: parallax.com and acroname.com Global: lightware.co.za
Looks great, where can i get one?
Question to laser Developer, when you mention limitations on water, related to transparency and other conditions, you mean that if flown on top of water, distance measure would not be precise?; or do you mean that you could be able to measure distance below water-surface level?. Thanks.
@Emin +1
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