Question

Writing point clouds including coordinate system information

  • 16 October 2018
  • 4 replies
  • 10 views
geojanmov

Hi FME community,

The behaviour of point cloud writers is a bit unclear. I want to set the srs for the point cloud exports (as "EPSG:28992+5709" or "EPSG:28992"). This works for LAS/LAZ exports with versions below 1.4. However, exports with version 1.4 do not carry the srs metadata.The method to determine the srs is the PDAL command: "pdal info .\\{filename} --metadata". This returns the following: ***plaatje*** I've tried writing the point cloud as: - LAZ 1.4 legacy: srs not set

 

- LAS 1.4 legacy: srs not set

 

- LAZ 1.4: srs not set

 

- LAS 1.4: srs not set

 

- LAZ 1.3: srs OK

 

- LAS 1.3: srs OK Is this behaviour normal?

4 replies

nathanatsafe
Rank
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Hi @geojan, thanks for your question.

 

I do notice the same behaviour as you for datasets output by FME, when inspecting with PDAL. Do you have other source point cloud datasets for v1.4, not created in FME, in which PDAL can read the metadata? Would you be able to share some samples here for further investigation? From the LAS documentation it appears that the SRS storage format may have changed between versions. It may in fact be a limitation in PDAL that some of this info is not read. By comparison, using LASTools, I have been able to read all coordinate system information output by FME, even when PDAL fails to.

 

 

Thanks,

 

Nathan
geojanmov

Hi @geojan, thanks for your question.

 

I do notice the same behaviour as you for datasets output by FME, when inspecting with PDAL. Do you have other source point cloud datasets for v1.4, not created in FME, in which PDAL can read the metadata? Would you be able to share some samples here for further investigation? From the LAS documentation it appears that the SRS storage format may have changed between versions. It may in fact be a limitation in PDAL that some of this info is not read. By comparison, using LASTools, I have been able to read all coordinate system information output by FME, even when PDAL fails to.

 

 

Thanks,

 

Nathan
Hi, @NathanAtSafe, Yes, we do (e.g. ftp://rockyftp.cr.usgs.gov/vdelivery/Datasets/Staged/Elevation/LPC/Projects/USGS_LPC_SD_MORiver_Woolpert_B1_2016_LAS_2018/laz/USGS_LPC_SD_MORiver_Woolpert_B1_2016_14TNP120300_LAS_2018.laz) and we can read out the coordinate system data of it with PDAL (see attachment). So, the strange behaviour of generating the LAZ v1.4 file in FME without SRS is not explained yet.

 

 

pdal-las-v14-with-srs.png

 

 

nathanatsafe
Rank
Badge +7
Hi, @NathanAtSafe, Yes, we do (e.g. ftp://rockyftp.cr.usgs.gov/vdelivery/Datasets/Staged/Elevation/LPC/Projects/USGS_LPC_SD_MORiver_Woolpert_B1_2016_LAS_2018/laz/USGS_LPC_SD_MORiver_Woolpert_B1_2016_14TNP120300_LAS_2018.laz) and we can read out the coordinate system data of it with PDAL (see attachment). So, the strange behaviour of generating the LAZ v1.4 file in FME without SRS is not explained yet.

 

 

pdal-las-v14-with-srs.png

 

 

Hi @geojan

 

Thanks for the data. I ran your v1.4 LAZ through FME and wrote it back out to v1.4 LAZ. From this FME output I can read the SRS in PDAL. Are you getting different results? I am beginning to wonder if the behaviour you're seeing occurs only when converting an older version to v1.4.

 

Best,

 

Nathan
geojanmov
Hi @geojan

 

Thanks for the data. I ran your v1.4 LAZ through FME and wrote it back out to v1.4 LAZ. From this FME output I can read the SRS in PDAL. Are you getting different results? I am beginning to wonder if the behaviour you're seeing occurs only when converting an older version to v1.4.

 

Best,

 

Nathan
Hi @NathanAtSafe

 

Thanks for your response. This indeed seems to be the case. Is this then something you can resolve in the LAZ (v1.4) writer or is this not possible due to the LAS schema?

 

Jan

 

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