Apollo: question about apollo map module

[freeclouds]

code version: apollo 3.0
Dear apollo developer,
when i trace planning module code,i find in navigation mode, apollo use relative map,
so planning module receive the map information from relative map, i don't understand the lane and the path what both of means, and segment ,
is there some document to describe lane 、path and segment information? such as lane-id and path-id,what is means?

[xinwf]

According to my understanding, those three concepts in map may can be shown as following:
This is a path from A to B

     ----------------------------------------------------------------------------------------
                        lane 0
     ----------------------------------------------------------------------------------------
A                       lane 1                                                                   B
     ----------------------------------------------------------------------------------------
        |       seg0     |       seg1       |       seg2       |
     ----------------------------------------------------------------------------------------

The path in our life, is something like xxxx Road, and the the lane is how many cars can run side by side at the same time, segment is the smaller unit defined by apollo team, I think maybe it is easier for the car to change lane or overtake.

---

update:
another reason that why the lane need to be segmented

[freeclouds]

@xinwf thanks，so when we use command :
python navigator.py path_demo_2.0.bag.txt.smoothed
and open relative map module ,planning module will receive one lane and one segment.
if use command:
python navigator.py path_demo_2.0.bag.txt.smoothed path_demo_2.0.bag.txt.smoothed
planning module will receive two lane: lane 0 and lane 1,and one segment.

[xinwf]

@freeclouds , no, in our relative map, there is no segment, just one lane, I think the segment concept is meaningful in HdMap, we haven't tried add two lanes by this way, I don't know whether it will success or not.