JT128 lidar

[marcofili80]

Hello,
I am working with JT128 lidar. In section “B.3 Start time of each block” of the user manual, the start time of each block t(m) is calculated as t0 -1888usec. In the SDK code, the 1888 value does not appear; only OTHER_BLOCK_NS_OFFSET2 (=111) is mentioned:

HesaiLidar_SDK_2.0/libhesai/UdpParser/src/udp1_4_parser.cc

Line 381 in 3346e74

block_ns_offset = PandarN::OTHER_BLOCK_NS_OFFSET2 * int((frame.block_num - blockid - 1) / (frame.return_mode < RETURN_MODE_MULTI ? 1 : 2));

Is this correct?

In section “3.1.4 Point cloud data analysis method” of the user manual, the horizontal angle is calculated as the azimuth of the current block plus the azimuth offset of the current firing channel. In the SDK code, the firetime corrections multiplied by the motor speed are taken into account for the calculation of the final azimuth angle in a similar way to the OT128 lidar:

HesaiLidar_SDK_2.0/libhesai/UdpParser/src/udp1_4_parser.cc

Line 415 in 3346e74

doubleToInt(GetFiretimesCorrection(channel_index, pTail->GetMotorSpeed() * (this->lidar_type_ != STR_OTHER ? 1.0 : 0.1),

Is this correct?

Thanks.

[changxingshuo]

Question 1: You are correct; this is our error, and we shall rectify the matter.
Question 2: The formula you have cited is the firetimes correction. Please refer to line 418 and the subsequent section on angle compensation calculations for the part you described.

[marcofili80]

Thank you for your reply.

Question 2:
Below, I have attached the horizontal angle computation of OT128...

and JT128 from the user manual:

Line 418 and the subsequent section correspond to of the OT128 section and of the JT128 section.

Line 413 and the subsequent section correspond to of the OT128 section. This section is not present in the JT128 user manual, but in the SDK it is also executed for this lidar.

[dinosshan]

Any updates on Question 2?