A laser rangefinder, also called an LRF or LIDAR, is an electronic device that uses the light emitted from a laser to measure distance. In its most common form, it is incorporated into hand-held devices for DIY enthusiasts to measure the size of a room in a house. But this application is just the tip of a very big iceberg for LRF technology, and LightWare focusses on more sophisticated, and more profitable, markets.

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Beam divergence is an angular measure of the increase in laser beam diameter over distance from the point where the laser beam exits the optics.

Most LightWare rangefinders have a beam divergence of less than 0.2°. This may vary slightly across products.

Simply put the beam pattern starts out as a square shape about the size of the lens and then slowly expands in all directions, becoming approximately circular in shape.

Beam divergence may be different on different axes.

The actual shape of the beam depends on many environmental factors, as well as energy dissipation around the edges of the beam, so a precise pattern cannot be predicted.

The linked graph gives an estimate of the nominal beam diameter at the half power points :: click here :: 

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S02 setup instructions are offered by ArduPilot and Pixhawk.

SF10 setup instructions are offered by ArduPilot.

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The SF10 family has been tested for radio frequency interference in accordance with MIL-STD-451C. The results are well within the required limits so that neither direct radiation nor secondary radiation from wiring should cause interference to on-board systems such as GPS and optical flow. See the SF10 manual for Electromagnetic interference (EMI) graphs.

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This method to adjust noise levels in SF30 models before software revision 7.0

In bright lighting conditions it is possible for readings to become slightly erratic or false results are displayed when there is no signal. This can be corrected as follows:

  •  Connect the SF30 to a PC or laptop using the USB cable only
  •  Press the <SPACE> key to stop readings from being taken and to show the main menu
  •  Press the capital <U> key to unlock the factory settings
  •  Press the capital <Y> key to confirm the unlocking command
  •  Press the arrow right key twice until the menu titled ** APD Settings ** is visible
  •  Write down the voltage value shown in the selection 1: APD breakdown xxx.xV
  •  Calculate a new breakdown voltage by subtracting 2 volts from the current value
  •  Enter the new breakdown voltage by pressing the <1> key then typing in the number followed by the <ENTER> key
  •  Check that the new value is entered correctly and has a value that is 2 V below the original value
  •  Press the <ESC> key to return to normal measuring
  •  Check that the readings are now stable and that there are no false results
  •  If there is still some noise repeat the steps above and reduce the APD breakdown by another 2 volts

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The solution below may be of use in the event that the LightWare Terminal program cannot connect to the laser rangefinder due to a com port error.

Windows allocates a com port to every device connected, but does not ever clear these allocations. This means that Windows will run out of available com ports once 255 ports have been allocated, requiring a clearing of the allocated com ports.

The below steps will show you how to easily clear the com ports using the LightWare Termminal program.

  1. Unplug all USB devices, excluding the mouse and keyboard.
  2. Run the LightWare Terminal program as an Administrator.
  3. Click on the "Laser" button on the top menu for the "Settings" menu to open.LightWare Terminal
  4. Under "COM Port Management" click on "Remove". Caution: There is no message once "Remove" has been clicked. Do not click again, but please wait for the program to complete the clearing process.LightWare Terminal
  5. A message will pop up that the “Ports were removed successfully.” Click okay and close the "Settings" menu.LightWare Terminal
  6. It may be necessary to restart your computer before the changes take effect.

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Reading altitude off a water surface is quite challenging, especially during bright sunshine. The laser signal can be lost within the water and sunshine reflecting off the water surface causes noise and false readings.

LightWare suggests changing the rangefinder’s settings before flying over water. This can be done either through the user manual or in flight, using the extensive command sets available for serial and I2C communication.

  1. Connect the rangefinder to the LightWare Terminal Program. The rangefinder will automatically display output data.
  2. Press the <SPACE> to stop the readings and display the menu.
    LightWare Terminal
  3. Press the <A> button to open the system menu. The recommended measuring mode for altitude over water is long range. This means the rangefinder spends more time searching for a return signal than in quick response mode.
    LightWare Terminal
  4. Press <M> to enter the filter menu.
  5. "p" indicates the amount of seconds the rangefinder will wait before returning a lost signal output.
    1 second = 20 readings and is sufficient for altitudes below 50 meters.
    For altitudes higher than 50 meters we recommend using 2 seconds as the return signal is lost more often over the longer range.  
    Press <P> and enter <2> and press <ENTER> again for the new setting to be accepted.
    LightWare Terminal
    LightWare Terminal
  6. Press <Q> to switch on the median filter.
    This median filter returns the most frequent result in a number of readings and is recommended for use over water due to the sunshine reflecting from the water surface as well as the lost signal conditions.LightWare Terminal

  7. Press <R> to set the filter size, or number of readings the rangefinder will use to determine the median output. Enter "20" and press <ENTER>LightWare Terminal
    The median filter will now use 20 readings and output the most frequent reading, which should discard false readings and temporary loss of signal.
    The maximum median filter size is 32 readings.
    LightWare Terminal

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