How to get the specific angle and distance information of an obstacle from ros topic?

[ccs-ros]

I have another question,what‘s the data in the message "ping"? Is the echo intensity value? If i want to get the specific angle and distance information of an obstacle，what shoud i do?

[jinkunw]

Check the definition of ping msg.

Basically, the image filed encodes the intensity of echo return at a specific range (row) and bearing (column). So pixel at the ith row and jth column in the image refers to intensity at bearings[j] and range_resolution x (i + 1).