all_separate_topics are the same

[HaroldMurcia]

Hi, I'm very interested on echo information. when I choose the "all_separate_topics" option, I get 3 separate point cloud in ROStopics messages, however when I graph them they contain the same information.

[rossctaylor]

Hi @HaroldMurcia - the three returns do not contain exactly the same information but many of the points will be the same because there were fewer than 3 returns detected. Here is the information from the User Guide:

The evaluation rules for assigning these labels are as follows:

• If no return pulses are detected, each of the three return values is 0.
• If one or more return pulses are detected:
  • Return 0: The first return value equals Maximum.
  • Return 1: The second return value equals Second Strongest. (But if there was only one return pulse, the return value equals Maximum.)
  • Return 2: The third return value equals Last, which may be equal to Second Strongest or Maximum.