Customizable metadata when writing COPC files

[wonder-sk]

Some pieces of metadata are not kept when a LAS/LAZ file is processed with untwine:

• global encoding - the bit on GPS time shift is not preserved
• creation time - hardcoded to day 1 of year 1
• X/Y/Z offset - untwine picks the offset itself (in the center of the data) rather than reusing the original one

[abellgithub]

Is this request just in the case of a single input file?

[hobu]

Is this request just in the case of a single input file?

Yeah. I was thinking of providing options to allow people to explicitly set the metadata rather than trying to mimic PDAL's forward behavior, which would be fraught.

[uclaros]

Is this request just in the case of a single input file?

For the cases of a single input file, which is always the case in QGIS, I think it makes sense to default to the following:

• preserving the gps time bit, as it allows proper interpretation of gps times for the file
• Creation year/day for a single file should be updated, as the las spec states: Day, expressed as an unsigned short, on which this file was created. This file applies to the copc output file.
• Since the scaling is preserved, it makes sense to also preserve the offsets.

I consider options to explicitly set the metadata as a quite advanced feature that the majority of users shouldn't need to deal with, as long as sane defaults are used.