[pdal] Way to cast dimension data type?

[Howard Butler]

I pushed the tag to trigger the pdal/pdal:latest docker image rebuild if you want to verify using that mechanism. Otherwise, you will have to build master yourself to confirm.

Thanks for the report Piero!

Howard

> On May 8, 2017, at 8:59 AM, Andrew Bell <andrew.bell.ia at gmail.com> wrote:
> 
> I opened this ticket:
> 
> https://github.com/PDAL/PDAL/issues/1584
> 
> It should be fixed shortly.
> 
> On Sat, May 6, 2017 at 5:36 PM, Piero Toffanin <pt at masseranolabs.com> wrote:
> Hello,
> 
> First let me say that PDAL rocks. I love it.
> I was wondering if there's a way to specify (cast) the data type of the X,Y,Z dimensions while reading a PLY file (so in effect override the type specified in the PLY header) in the PDAL pipeline.
> 
> I have an input PLY file (untransformed.ply) that has the header:
> 
> ply
> format ascii 1.0
> [ .... ]
> property float x
> property float y
> property float z
> [ .... ]
> 
> And coordinate points with ~5 digits of precision.
> 
> 1.13759 12.1322 162.786 
> [ .... ]
> When I try to apply the following transform (add a east/north offset):
> {
>   "pipeline": [
>     "untransformed.ply",
>     {
>       "matrix": "1 0 0 576705 0 1 0 5188170 0 0 1 0 0 0 0 1",
>       "type": "filters.transformation"
>     },
>     {
>       "a_srs": "EPSG:32615",
>       "filename": "transformed.las",
>       "offset_x": "576705",
>       "offset_y": "5188170",
>       "offset_z": "0"
>     }
>   ]
> }
> There's a loss of precision (I get a "grid-like" output, see https://cloud.githubusercontent.com/assets/1951843/25507885/9cd01d12-2b7c-11e7-9c54-0e219dae4f05.png). I think it's because the matrix transformation code here https://github.com/PDAL/PDAL/blob/dd97a033c5d487000e200304a7619e9978de6ae2/filters/TransformationFilter.cpp#L106 correctly treats points as floats.
> Changing the PLY header to:
> 
> ply
> format ascii 1.0
> [ .... ]
> property double x
> property double y
> property double z
> [ .... ]
> 
> Produces the expected output (no grid-like output).
> I was wondering if I could force the dimensions to be treated as a double directly from PDAL? Or perhaps is there interest in adding a flag (cast to dimension) in PDAL's PLY reader (I'd be happy to contribute to it)?
> More information about the background of this issue is also available here: https://github.com/OpenDroneMap/OpenDroneMap/issues/522
> 
> Thank you for any information you might have!
> 
> -Piero
> 
> 
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> 
> 
> -- 
> Andrew Bell
> andrew.bell.ia at gmail.com
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