[pdal] Is PDAL capable of producing Lidar grid metrics?

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[pdal] Is PDAL capable of producing Lidar grid metrics?

Aaron Poznanovic
Greetings,

This is a follow-up to a question posted over at GIS Stack Exchange (http://gis.stackexchange.com/questions/175454/are-pdal-or-pcl-capable-of-producing-lidar-grid-metrics). I'm curious what functionality or approach one would take with PDAL to calculate Lidar grid metrics? 

FUSION is currently the best available set of tools that I know of for calculating Lidar grid metrics, which are useful for describing forest structure (http://forsys.cfr.washington.edu/fusion/fusionlatest.html). From the FUSION documentation (page 70 from the documentation http://forsys.cfr.washington.edu/fusion/FUSION_manual.pdf):

GridMetrics computes a series of descriptive statistics for a LIDAR data set. Output is a raster (grid) represented in database form with each record corresponding to a single grid cell.

Essentially, I'm interested in producing a raster dataset where each cell represents summarized descriptive statistics for the Lidar point cloud such as cover, skewness, 75th percentile, etc (all of the grid metrics I'm after are available on the FUSION documentation. Is this currently possible, or recommended, with PDAL, or would this require other libraries? Many thanks in advance.

Best Regards,

-Aaron

Currently


Aaron J. Poznanovic, GISP
Principal Consultant
Red Fox GIS & Remote Sensing
(218) 387-4050



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Re: [pdal] Is PDAL capable of producing Lidar grid metrics?

Rémi Cura
Hey,
I do something similar with pgpointcloud.
I grou points by patch that are cells in a grid,
then I compute statistics about each patch.
Cheers,
Rémi-C

2016-09-01 15:22 GMT+02:00 Aaron Poznanovic <[hidden email]>:
Greetings,

This is a follow-up to a question posted over at GIS Stack Exchange (http://gis.stackexchange.com/questions/175454/are-pdal-or-pcl-capable-of-producing-lidar-grid-metrics). I'm curious what functionality or approach one would take with PDAL to calculate Lidar grid metrics? 

FUSION is currently the best available set of tools that I know of for calculating Lidar grid metrics, which are useful for describing forest structure (http://forsys.cfr.washington.edu/fusion/fusionlatest.html). From the FUSION documentation (page 70 from the documentation http://forsys.cfr.washington.edu/fusion/FUSION_manual.pdf):

GridMetrics computes a series of descriptive statistics for a LIDAR data set. Output is a raster (grid) represented in database form with each record corresponding to a single grid cell.

Essentially, I'm interested in producing a raster dataset where each cell represents summarized descriptive statistics for the Lidar point cloud such as cover, skewness, 75th percentile, etc (all of the grid metrics I'm after are available on the FUSION documentation. Is this currently possible, or recommended, with PDAL, or would this require other libraries? Many thanks in advance.

Best Regards,

-Aaron

Currently


Aaron J. Poznanovic, GISP
Principal Consultant
Red Fox GIS & Remote Sensing
(218) 387-4050



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Re: [pdal] Is PDAL capable of producing Lidar grid metrics?

Bradley Chambers
In reply to this post by Aaron Poznanovic
Aaron,

This is absolutely possible; it just doesn't exist out of the box today. We do something similar in our DerivativeWriter today (https://github.com/PDAL/PDAL/blob/master/io/derivative/DerivativeWriter.cpp). That may be a good place to look for inspiration. I think in the end you are looking for a GridMetricsWriter though. Are you needing a full replacement of the FUSION function? Or just a few select metrics?

Brad

On Thu, Sep 1, 2016 at 9:22 AM Aaron Poznanovic <[hidden email]> wrote:
Greetings,

This is a follow-up to a question posted over at GIS Stack Exchange (http://gis.stackexchange.com/questions/175454/are-pdal-or-pcl-capable-of-producing-lidar-grid-metrics). I'm curious what functionality or approach one would take with PDAL to calculate Lidar grid metrics? 

FUSION is currently the best available set of tools that I know of for calculating Lidar grid metrics, which are useful for describing forest structure (http://forsys.cfr.washington.edu/fusion/fusionlatest.html). From the FUSION documentation (page 70 from the documentation http://forsys.cfr.washington.edu/fusion/FUSION_manual.pdf):

GridMetrics computes a series of descriptive statistics for a LIDAR data set. Output is a raster (grid) represented in database form with each record corresponding to a single grid cell.

Essentially, I'm interested in producing a raster dataset where each cell represents summarized descriptive statistics for the Lidar point cloud such as cover, skewness, 75th percentile, etc (all of the grid metrics I'm after are available on the FUSION documentation. Is this currently possible, or recommended, with PDAL, or would this require other libraries? Many thanks in advance.

Best Regards,

-Aaron

Currently


Aaron J. Poznanovic, GISP
Principal Consultant
Red Fox GIS & Remote Sensing
(218) 387-4050


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Re: [pdal] Is PDAL capable of producing Lidar grid metrics?

Howard Butler-3
As I mentioned in the Stack Exchange thread, and Brad mentioned below, this isn't currently possible out of the box with PDAL. I would ask what you are hoping to get by having this capability in PDAL rather than building a tool chain that includes FUSION + PDAL + other tools. Maybe it would be helpful to take a step back and describe how PDAL statistics computation would fit within a larger context.

Most of PDAL's current "characterization" filters are about generating primitive computations for algorithms such as slope, ground, etc. There's things like coplanarity, projection, regression, sampling, and normal computation [1]. These are "per-point" type statistics rather than summaries, however, and are focused on the positional geometry of the point in relation(s) to its neighbors. Brad described the derivative writer, which does some typical surface summaries, and it would be a good place to start on an implementation if you were sufficiently motivated.

PDAL's statistics filter [2] was recently updated to add kurtosis, skewness, variance, etc (no percentiles). You *might* be able to use that in combination with some sort moving window bounding geometry along with the crop filter [3], but this would be quite laborious and probably quite slow. Rémi's pgpointcloud approach seems viable and might be useful for other reasons, depending on what you want to do.

So, plenty of options but nothing that just does it.

Howard

[1] http://www.pdal.io/stages/filters.html
[2] http://www.pdal.io/stages/filters.stats.html
[3] http://www.pdal.io/stages/filters.crop.html

> On Sep 1, 2016, at 8:37 AM, Bradley Chambers <[hidden email]> wrote:
>
> Aaron,
>
> This is absolutely possible; it just doesn't exist out of the box today. We do something similar in our DerivativeWriter today (https://github.com/PDAL/PDAL/blob/master/io/derivative/DerivativeWriter.cpp). That may be a good place to look for inspiration. I think in the end you are looking for a GridMetricsWriter though. Are you needing a full replacement of the FUSION function? Or just a few select metrics?
>
> Brad
>
> On Thu, Sep 1, 2016 at 9:22 AM Aaron Poznanovic <[hidden email]> wrote:
> Greetings,
>
> This is a follow-up to a question posted over at GIS Stack Exchange (http://gis.stackexchange.com/questions/175454/are-pdal-or-pcl-capable-of-producing-lidar-grid-metrics). I'm curious what functionality or approach one would take with PDAL to calculate Lidar grid metrics?
>
> FUSION is currently the best available set of tools that I know of for calculating Lidar grid metrics, which are useful for describing forest structure (http://forsys.cfr.washington.edu/fusion/fusionlatest.html). From the FUSION documentation (page 70 from the documentation http://forsys.cfr.washington.edu/fusion/FUSION_manual.pdf):
>
> GridMetrics computes a series of descriptive statistics for a LIDAR data set. Output is a raster (grid) represented in database form with each record corresponding to a single grid cell.
>
> Essentially, I'm interested in producing a raster dataset where each cell represents summarized descriptive statistics for the Lidar point cloud such as cover, skewness, 75th percentile, etc (all of the grid metrics I'm after are available on the FUSION documentation. Is this currently possible, or recommended, with PDAL, or would this require other libraries? Many thanks in advance.
>
> Best Regards,
>
> -Aaron
>
> Currently
>
>
> Aaron J. Poznanovic, GISP
> Principal Consultant
> Red Fox GIS & Remote Sensing
> (218) 387-4050
> www.redfoxgis.com
>
>
> _______________________________________________
> pdal mailing list
> [hidden email]
> http://lists.osgeo.org/mailman/listinfo/pdal
> _______________________________________________
> pdal mailing list
> [hidden email]
> http://lists.osgeo.org/mailman/listinfo/pdal

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Re: [pdal] Is PDAL capable of producing Lidar grid metrics?

wenzeslaus
In reply to this post by Aaron Poznanovic
Hi Aaron,

On Thu, Sep 1, 2016 at 9:22 AM, Aaron Poznanovic <[hidden email]> wrote:

GridMetrics computes a series of descriptive statistics for a LIDAR data set. Output is a raster (grid) represented in database form with each record corresponding to a single grid cell.

Essentially, I'm interested in producing a raster dataset where each cell represents summarized descriptive statistics for the Lidar point cloud such as cover, skewness, 75th percentile, etc (all of the grid metrics I'm after are available on the FUSION documentation. Is this currently possible, or recommended, with PDAL, or would this require other libraries? Many thanks in advance.

this is what r.in.lidar in GRASS GIS is doing:

https://grass.osgeo.org/grass72/manuals/r.in.lidar.html
method: n, min, max, range, sum, mean, stddev, variance, coeff_var, median, percentile, skewness, trimmean
(available also through QGIS processing since Jun 2)

Currently, r.in.lidar is using libLAS. I would like to rewrite it (or would like somebody else to rewrite it) to use PDAL instead of libLAS.

The idea here is that at the end you have your data in GRASS GIS where you can do the subsequent raster analysis (although you can of course import or link the raster created elsewhere) but PDAL (or currently only libLAS) is used for all point cloud processing in the background. This is something like a tool chain which Howard mentions but hidden from the user.

(If somebody is interested in working towards that, please let me know anytime.)

Vaclav

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Re: [pdal] Is PDAL capable of producing Lidar grid metrics?

jfprieur
In reply to this post by Howard Butler-3
Believe he is trying to move entirely to Linux and is looking for a FUSION metrics replacement since it does not run in Linux. SPDLib looks interesting. If you have access to LAStools the LAScanopy tool does these metrics, although I am unsure if the free version has full functionality.

On Thu, Sep 1, 2016 at 9:42 AM Howard Butler <[hidden email]> wrote:
As I mentioned in the Stack Exchange thread, and Brad mentioned below, this isn't currently possible out of the box with PDAL. I would ask what you are hoping to get by having this capability in PDAL rather than building a tool chain that includes FUSION + PDAL + other tools. Maybe it would be helpful to take a step back and describe how PDAL statistics computation would fit within a larger context.

Most of PDAL's current "characterization" filters are about generating primitive computations for algorithms such as slope, ground, etc. There's things like coplanarity, projection, regression, sampling, and normal computation [1]. These are "per-point" type statistics rather than summaries, however, and are focused on the positional geometry of the point in relation(s) to its neighbors. Brad described the derivative writer, which does some typical surface summaries, and it would be a good place to start on an implementation if you were sufficiently motivated.

PDAL's statistics filter [2] was recently updated to add kurtosis, skewness, variance, etc (no percentiles). You *might* be able to use that in combination with some sort moving window bounding geometry along with the crop filter [3], but this would be quite laborious and probably quite slow. Rémi's pgpointcloud approach seems viable and might be useful for other reasons, depending on what you want to do.

So, plenty of options but nothing that just does it.

Howard

[1] http://www.pdal.io/stages/filters.html
[2] http://www.pdal.io/stages/filters.stats.html
[3] http://www.pdal.io/stages/filters.crop.html

> On Sep 1, 2016, at 8:37 AM, Bradley Chambers <[hidden email]> wrote:
>
> Aaron,
>
> This is absolutely possible; it just doesn't exist out of the box today. We do something similar in our DerivativeWriter today (https://github.com/PDAL/PDAL/blob/master/io/derivative/DerivativeWriter.cpp). That may be a good place to look for inspiration. I think in the end you are looking for a GridMetricsWriter though. Are you needing a full replacement of the FUSION function? Or just a few select metrics?
>
> Brad
>
> On Thu, Sep 1, 2016 at 9:22 AM Aaron Poznanovic <[hidden email]> wrote:
> Greetings,
>
> This is a follow-up to a question posted over at GIS Stack Exchange (http://gis.stackexchange.com/questions/175454/are-pdal-or-pcl-capable-of-producing-lidar-grid-metrics). I'm curious what functionality or approach one would take with PDAL to calculate Lidar grid metrics?
>
> FUSION is currently the best available set of tools that I know of for calculating Lidar grid metrics, which are useful for describing forest structure (http://forsys.cfr.washington.edu/fusion/fusionlatest.html). From the FUSION documentation (page 70 from the documentation http://forsys.cfr.washington.edu/fusion/FUSION_manual.pdf):
>
> GridMetrics computes a series of descriptive statistics for a LIDAR data set. Output is a raster (grid) represented in database form with each record corresponding to a single grid cell.
>
> Essentially, I'm interested in producing a raster dataset where each cell represents summarized descriptive statistics for the Lidar point cloud such as cover, skewness, 75th percentile, etc (all of the grid metrics I'm after are available on the FUSION documentation. Is this currently possible, or recommended, with PDAL, or would this require other libraries? Many thanks in advance.
>
> Best Regards,
>
> -Aaron
>
> Currently
>
>
> Aaron J. Poznanovic, GISP
> Principal Consultant
> Red Fox GIS & Remote Sensing
> (218) 387-4050
> www.redfoxgis.com
>
>
> _______________________________________________
> pdal mailing list
> [hidden email]
> http://lists.osgeo.org/mailman/listinfo/pdal
> _______________________________________________
> pdal mailing list
> [hidden email]
> http://lists.osgeo.org/mailman/listinfo/pdal

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Re: [pdal] Is PDAL capable of producing Lidar grid metrics?

Newcomb, Doug
In reply to this post by Aaron Poznanovic
Aaron,
You can do most of this in GRASS GIS 7.2svn using r.in.lidar to create individual rasters for each metric. 
https://grass.osgeo.org/grass72/manuals/r.in.lidar.html .  It corrects the z values to height above ground when you designate a base raster DEM and you can give it a text list of las/laz files to process as a single unit.  I'm using it to process county-wide QL2 density in North Carolina for canopy metrics and have processed data in 10billion point blacks at a time.

I find canopy cover to be a somewhat subjective metric , based on bare earth points, which varies depending on the method used to extract bare earth points.

Doug

Doug 


On Thu, Sep 1, 2016 at 9:22 AM, Aaron Poznanovic <[hidden email]> wrote:
Greetings,

This is a follow-up to a question posted over at GIS Stack Exchange (http://gis.stackexchange.com/questions/175454/are-pdal-or-pcl-capable-of-producing-lidar-grid-metrics). I'm curious what functionality or approach one would take with PDAL to calculate Lidar grid metrics? 

FUSION is currently the best available set of tools that I know of for calculating Lidar grid metrics, which are useful for describing forest structure (http://forsys.cfr.washington.edu/fusion/fusionlatest.html). From the FUSION documentation (page 70 from the documentation http://forsys.cfr.washington.edu/fusion/FUSION_manual.pdf):

GridMetrics computes a series of descriptive statistics for a LIDAR data set. Output is a raster (grid) represented in database form with each record corresponding to a single grid cell.

Essentially, I'm interested in producing a raster dataset where each cell represents summarized descriptive statistics for the Lidar point cloud such as cover, skewness, 75th percentile, etc (all of the grid metrics I'm after are available on the FUSION documentation. Is this currently possible, or recommended, with PDAL, or would this require other libraries? Many thanks in advance.

Best Regards,

-Aaron

Currently


Aaron J. Poznanovic, GISP
Principal Consultant
Red Fox GIS & Remote Sensing
(218) 387-4050



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---------------------------------------------------------------------------------------------------------
The opinions I express are my own and are not representative of the official policy of the U.S.Fish and Wildlife Service or Dept. of the Interior.   Life is too short for undocumented, proprietary data formats. As a federal employee, my email may be subject to FOIA request.

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Re: [pdal] Is PDAL capable of producing Lidar grid metrics?

Howard Butler-3
In reply to this post by jfprieur

> On Sep 1, 2016, at 9:11 AM, Jean-Francois Prieur <[hidden email]> wrote:
>
> Believe he is trying to move entirely to Linux and is looking for a FUSION metrics replacement since it does not run in Linux.

Is it not possible to run FUSION in Wine (which is the way most end up running LAStools in Linux too)?


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Re: [pdal] Is PDAL capable of producing Lidar grid metrics?

jfprieur
Forgot about Wine (haven`t had to use it in ages), of course it should run that way. Apologies.

On Thu, Sep 1, 2016 at 10:21 AM Howard Butler <[hidden email]> wrote:

> On Sep 1, 2016, at 9:11 AM, Jean-Francois Prieur <[hidden email]> wrote:
>
> Believe he is trying to move entirely to Linux and is looking for a FUSION metrics replacement since it does not run in Linux.

Is it not possible to run FUSION in Wine (which is the way most end up running LAStools in Linux too)?


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