[pdal] Target Aliged Pixels (tap) for the GDAL driver

[James Klassen]

You can calculate and pass in your own "--writers.gdal.bounds" and get
aligned pixels.

(By doing this, I am able to round trip a DEM into a point cloud in PDAL
and back into a DEM losslessly.)



On Thu, May 7, 2020, 16:16 Håkon Åmdal <hakon at aamdal.com> wrote:

> Hi there,
>
> I'm currently working on a LIDAR data project where we classify "high
> vegetation" and buildings using PDAL. We convert them to rasters before we
> send them downstream.
>
> Now, we are looking to combine the rasters generated with
> satellite imagery. For this project, we believe it's important to have an
> 1:1 mapping between the pixels in the different sources.
>
> To align our satellite images with the underling projection, we use the
> "-tap" option in gdalwarp. However, no such feature exists for the
> GDAL-writer in PDAL. Which means the pixels are offset by up to half a
> meter (for UTM and 1.0 scale).
>
> I think we can overcome the above issue by using PDAL to generate a much
> higher resolution TIF file (say 0.1) and then resample with gdalwarp and
> the "-tap" option. Or even just keep the resolution, just use gdalwarp to
> resample.
>
> I was wondering if a similar "-tap" option belongs in PDAL, and how that
> would look like? I initially thought it was argument passed to the driver,
> but AFAIK the pixel alignment happens before it is passed to the driver. If
> I understand it correctly, it would then be an extra option to be passed to
> the "writers.gdal" component.
>
> I'd love to contribute, but I'm no C++ developer.
>
> Håkon
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