[pdal] [PDAL] PGPointCloud: Updating point info

[Jean-Francois Prieur]

Hello,

Newbie to PostGIS/PGPointCLoud, used to work with MySQL many moons ago so
know just enough to be dangerous!

I am working in remote sensing research , precision forestry to be specific.

We use ALS data and tree crown segmentation on the resulting canopy height
models to segment individual trees. We then use the shapefile to extract
the points from the las files. This is done using Python, it works but it
is a slow process and we have to redo it when we want to update the info on
our points.

We are looking into doing a lot of this in PostGIS and have succesfully
imported our las files using the awesome documentation provided. So we have
a working pipeline LAS->PDAL->pgPointCloud and can perform all kinds of
queries on the data so that part works.

We can do the spatial join between the shapefiles containing all our
individual crowns (there can be thousands) and then extracting all the
points under those. What we would like to do is update all the points
selected under a crown with that crowns ID so we do not have to do these
spatial joins all the time eg. we can just query the crown number and get
the points that way. We can select all the points, we just cannot update
the points with the proper info. The spatial join is quite long with
thousands of crowns, we would like to only run it once, update the points
with the proper crown ID and then work with the data that way.

I believe part of the solution is the shema used in the pipeline process, I
think we would have to add a field in a new schema for the crownid which
could then be updated with the crown id. Just not quite sure how to get
there.

Not afraid to learn on my own and digging in, just in need of a push in the
right direction!

Thanks,
JF Prieur
PhD Candidate Remote Sensing
Université de Sherbrooke
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