30
Byte 11
represents the second echo strength, and the value range is 0-255. (Echo
strength can reflect the energy reflection characteristics of the measured object in the
actual measurement environment. Therefore, the echo strength can be used to
distinguish objects with different reflection characteristics.)
Byte 12, Byte 13 and Byte 14
represent the distance value of the third echo, the most
significant byte of which is stored at the smallest memory address and the least
significant byte at the largest. The two high-order bytes are the integer part, whose unit
is “cm”; and the last byte is the decimal part, whose unit is 1/256 cm. To analyze the
distance value, for example: the distance value in the obtained data packet is
represented by the hexadecimal number 0x02, 0x18, 0x32, and the first two bytes are
composed of 16-bit unsigned data, that is: 0x0218, which is converted to decimal
distance value: 536 cm. The last byte is the decimal part, 0x32 equals 50 in decimal,
that is, 50*1/256 cm = 0.1953125 cm. Then the two parts add up to 536. 1953125 cm.
Byte 15
represents the third echo strength, and the value range is 0-255. (Echo strength
can reflect the energy reflection characteristics of the measured object in the actual
measurement environment. Therefore, the echo strength can be used to distinguish
objects with different reflection characteristics.)
7.3 Cartesian Coordinate Representation
To obtain the vertical angle, horizontal angle and distance parameters of the Lidar, the
angle and distance information in polar coordinates can be converted to the x, y, z
coordinates in the right-hand Cartesian coordinate system. The conversion relationship
is shown in the following formula:
{
𝑥 = 𝑟 cos 𝛼 cos 𝜃;
𝑦 = 𝑟 cos 𝛼 sin 𝜃;
𝑧 = 𝑟 sin 𝛼
In the above formula, r is the distance, α is the vertical angle, θ is the horizontal rotation
angle (the horizontal correction angle needs to be considered when calculating). And x,
y, and z are the coordinates of the polar coordinates projected onto the x, y, and z axes.
Figure 7.1 Coordinate Mapping
