RiParameter
Last updated
Last updated
RiParameter is a helpful tool for planning acquisition and can show you how PRR, Scan rate, altitude, and speed will affect your point cloud. This manual covers how to use RiParameter in Interactive mode.
Open RiParameter, select your sensor model and set Project Type to Interactive mode:
RiParameter takes in inputs such as laser pulse repetition rate (i.e. pulses per second or PRR), flight altitude and speed, and then outputs statistics, such as number of points per meter squared (PPSM), laser range utilization, and more. In general, we will use RiParameter by specifying a set of input parameters on the left half, then clicking the blue Play button and observing the result on the right half:
We will begin inputting settings into the input side of RiParameter.
Terrain variation and reflectivity can impact the results of a lidar scan. If flying at a constant altitude, terrain variation will change the lidar's range to target. Target reflectance changes the operating range of the lidar.
For a basic use case, we will assume no terrain variation and minimum reflectance of 20%:
Most natural targets have a reflectance of about 20%. If you are scanning a man-made area, a minimum reflectance of 10% should be used due to the presence of very low reflectivity targets, such as asphalt roads and asphalt shingle roofs.
At the bottom of the input page, specify your flight AGL and speed:
If you are using RiParameter to determine the ideal flight AGL, just enter an initial value that seems reasonable. We can modify this value later.
Lastly, we will specify Scanner Settings. First specify a PRR. Then, click AVG to compute the proper Scan Rate:
This is one of the most important use cases of RiParameter - based on your PRR, flight altitude, and speed, RiParameter can compute the proper scan rate (scan rate is often referred to as "mirror speed" or "line speed").
We can now click the blue play button and RiParameter will compute an output:
On the left, output statistics are shown, and on the right an example of the point distribution is shown.
Lidar density is usually lowest at the edge of the swath, and highest at nadir. Our Min., Avg., and Max., estimated point density is displayed. The point distance associated with this density (point distance being the distance between points within the same scan line) is also shown:
Note that our Line Distance is roughly equal to our average point distance:
This is because we previously computed scan rate based on laser and flight settings. If your line distance is approximately equal to your point distance, you should have a properly distributed point cloud. If you are flying faster than the appropriate scan rate your line distance will be greater than your point distance. If you are flying slower than the appropriate scan rate your point distance will be greater than your line distance.
Laser Safety and range info are computed. None of these fields should ever exceed 100%.
NOHD and ENOHD refer to eye safety standards. These are typically only concerns with bathymetric lidar sensors.
Max. Meas. Range is important for all scanners. This tells you whether the laser is capable of operating at the specified altitude. If you exceed 100% Max. Meas. Range, you will need to either fly at a lower AGL or lower the PRR (lidar scanners can range further when pulsing slower). You can observe this by lowering the PRR in the Scanner Settings menu.
Scanrate-range-prod. refers to the relationship between the mirror speed and range distance. The scan mirror inside the lidar directs the outgoing lidar pulse towards the ground in a scan line pattern. This same mirror also directs the incoming lidar return back to the receiver. With very fast mirror speeds and very long distances to targets (i.e. high altitude flights), it's possible that the mirror rotates away from the incoming lidar pulse, and thus the return is not recorded by the receiver.
