How
Does LiDAR Work - Scanner Systems
Once the data has been collected,
the computer must do some calculations to figure
out the distance that the laser traveled. These
calculations aren't incredibly difficult but they
must be done correctly to ensure that the proper
elevation is received. The first calculation is as
follows:
Distance Above
Ground = [(Time of Travel) x (Speed of Light)] / 2
The reason for the division by two
is because the laser must travel the initial pulse
and then the return distance, which is two lengths
of the distance we are trying to calculate. (4)
Another thing that the scanner
systems are going to calculate is the elevation of
the ground beneath the plane and in order to do
this, the positioning systems must be used to find
the plane's altitude. The calculation then
becomes:
Ground Elevation
= Altitude - Distance Above Ground
Although, this equation is
simplified because the calculation of the altitude
uses the data from the positioning systems to
calculate the pulse angle. The pulse angle is
relevant since the laser isn't going to be coming
out of the plane every time at ninety degrees, the
sweeping motion is changing the angle. This is
actually referred to as NADIR (directly below) and
Off-NADIR. The positioning systems will be talked
about on the next page.
