lasvalidate and points flagged as synthetic

Martin Isenburg

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Jan 25, 2019, 3:24:23 AM1/25/19

to The LAS room - a friendly place to discuss specifications of the LAS format, LAStools - efficient command line tools for LIDAR processing

Hello,

I've received an interesting suggestion about changing the way that lasvalidate works for synthetic points (those whose "synthetic flag" is set). As these points may not have GPS time stamps, scan angles, echo attribute, or point source IDs they could be excluded from the "fail" mechanism. Currently lasvalidate does not distinguish between regular or synthetic points and will fail any LAS / LAZ file where the synthetic points violate the LAS specification (i.e. return counts are not set).

Should lasvalidate ignore synthetic points, thus allowing points clouds that are not fully attributed to pass the check as long as those points without all attributes are marked synthetic ... ?

Regards from the Philippines,

Martin

Lewis Graham

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Jan 25, 2019, 10:14:58 AM1/25/19

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Hi Martin,

Yes, for sure. Points with the Synthetic flag should be bypassed in validity checks.

Enjoy the Philippines!

Lewis

Lewis Graham

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Madison, AL 35758 USA

256-461-8289

www.geocue.com

Software tools for LIDAR & Drone Mapping

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Evon Silvia

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Jan 25, 2019, 5:04:54 PM1/25/19

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Allowing a switch to ignore (or suppress?) validation of synthetic points makes sense to me.

Evon

Martin Isenburg

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Jan 26, 2019, 4:23:02 AM1/26/19

to The LAS room - a friendly place to discuss specifications of the LAS format, LAStools - efficient command line tools for LIDAR processing

Hello,

I would side with Lewis on that one. The default behavior should exclude *certain* checks for synthetic points that might be taken from SRTM grids or taken manually to fill voids or something similar. Which checks should be excluded? Which checks should stay? And maybe a LAS file containing only (or over 50% of) synthetic points should fail?

Ignore checking those:

* return count

* scan angle

* ...

But continue checking these:

* xyz coordinates within LAS header bounding box

* ...

Regards,

Martin @rapidlasso

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