Difference of x, y coordinates of dual return mode #88

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2020-09-11T14:49:31+02:00

mbcel commented

2020-09-11 14:49:31 +02:00

(Migrated from github.com)

I am currently investigating the Dual Return mode for the Horizon Lidar and found that in the SDK the data field for such point (LivoxDualExtendRawPoint) does contain 2 x and 2 y values. In my understanding this information could be reduced to only 1 x,y and 2 z values, because both z values are returned from the exact same direction (e.g. by scaling x2 = (x1 / z1) * z2). Is this a valid or is this wrong and there is indeed a possible different direction also for the x,y values?

Furthermore, what are the returned dual values: first and last return, or strongest and last return or something like this?

I am currently investigating the Dual Return mode for the Horizon Lidar and found that in the SDK the data field for such point (LivoxDualExtendRawPoint) does contain 2 x and 2 y values. In my understanding this information could be reduced to only 1 x,y and 2 z values, because both z values are returned from the exact same direction (e.g. by scaling x2 = (x1 / z1) * z2). Is this a valid or is this wrong and there is indeed a possible different direction also for the x,y values? Furthermore, what are the returned dual values: first and last return, or strongest and last return or something like this?

Livox-SDK commented

2021-07-09 16:01:10 +02:00

(Migrated from github.com)

Hi mbcel，

For dual return mode, two points will be written at the exact same direction.
First return mode: the closest point will be counted
Strongest return mode: the most "powerful" point along the path will be counted (e.g. If a high reflection object placed a bit further, it may be counted rather than a closer low reflation rate object)
Dual return mode: since the laser beam is not exactly a point, is an area, so there will be a situation that a beam detect 2 things at the same time, if dual return modes on, both points will be counted

Hi mbcel， For dual return mode, two points will be written at the exact same direction. First return mode: the closest point will be counted Strongest return mode: the most "powerful" point along the path will be counted (e.g. If a high reflection object placed a bit further, it may be counted rather than a closer low reflation rate object) Dual return mode: since the laser beam is not exactly a point, is an area, so there will be a situation that a beam detect 2 things at the same time, if dual return modes on, both points will be counted

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Reference: mmr/Livox-SDK#88