Extract LAS (3D Analyst)

Summary

Creates new LAS files from point cloud data in a LAS dataset or point cloud scene layer.

Illustration

Usage

• This tool can be used to create new LAS files from a subset of a LAS dataset or point cloud scene layer by specifying a processing extent, extraction boundary, or both. When a processing extent is provided with an extraction boundary, the intersection of both will define the coverage of the extracted LAS files. A point filter can be applied to the input point cloud data if only a subset of points are necessary in the output LAS files. The source point cloud can be filtered to specify the points based on any combination of classification codes, class flags, and return values. The point filters for the LAS dataset and point cloud scene layer can be defined by loading the layer into an active map or scene and specifying the filters on the Layer Properties dialog box. Additionally, you can create a layer with point filters for the LAS dataset using the Make LAS Dataset Layer tool.

• If the spatial reference is defined for the input point cloud, you can reproject the output LAS data created by this tool to a different horizontal and vertical coordinate system by setting the Output Coordinate System environment. The spatial reference of a .las file can be defined in either its header or an auxiliary .prj file using the well-known text (WKT) convention. The .prj file must reside in the same location as the .las file and have the same name as the .las file. When present, the .prj file will override the spatial reference information in the .las file header. You can create .prj files for .las files with missing or incorrectly defined spatial reference using the Define Projection tool for an individual .las or .zlas file or the Create LAS Dataset tool with the PRJ option enabled.

• It is not uncommon for LAS point records to be stored in the .las file in a binary sequence that does not correspond with the spatial clustering of the points. When data of such distribution is queried, it can result in less efficient access to the binary records that represent the LAS points. Rearranging the points in the resulting .las file will optimize the data for visualization and other spatial operations. Statistics will automatically be calculated when the rearrange option is enabled. If you choose not to rearrange the LAS points, you can enable or disable the calculation of statistics. Calculating statistics will optimize spatial queries and provide a summary of the class codes and return values that are present in the .las file. However, it will also add time to the processing of this tool. If the resulting .las files will not be used in ArcGIS, you can disable the calculation of statistics so that the tool can execute faster.

Parameters

Dialog

Label	Explanation	Data Type
Input Point Cloud	The LAS dataset or point cloud scene layer to process.	LAS Dataset Layer; Scene Service Layer; File
Target Folder	The existing folder to which the output .las files will be written.	Folder
Processing Extent (Optional)	The extent of the data that will be evaluated. Default—The extent will be based on the maximum extent of all participating inputs. This is the default. Union of Inputs—The extent will be based on the maximum extent of all inputs. Intersection of Inputs—The extent will be based on the minimum area common to all inputs. Current Display Extent—The extent is equal to the visible display. The option is not available when there is no active map. As Specified Below—The extent will be based on the minimum and maximum extent values specified. Browse—The extent will be based on an existing dataset.	Extent
Extraction Boundary (Optional)	A polygon boundary that defines the area of the .las files that will be clipped.	Feature Layer
Process entire LAS files that intersect extent (Optional)	Specifies how the area of interest will be used in determining how .las files will be processed. The area of interest is defined by the Processing Extent parameter value, the Processing Boundary parameter value, or a combination of both. Unchecked—Only LAS points that intersect the area of interest will be processed. This is the default. Checked—If any portion of a .las file intersects the area of interest, all the points in that .las file, including those outside the area of interest, will be processed.	Boolean
Output File Name Suffix (Optional)	The text that will be appended to the name of each output .las file. Each file will inherit its base name from its source file, followed by the suffix specified in this parameter.	String
Remove Variable Length Records (Optional)	Specifies whether variable length records (VLRs) will be removed. Each .las file may potentially contain a set of VLRs that were added by the software that produced it. The meaning of these records is typically only known by the originating software. Unless the output LAS data will be processed by an application that understands this information, retaining the VLRs may not provide any value-added functionality. Removing the VLRs can potentially save significant disk space depending on their total size and the number of files containing them. Unchecked—The variable length records in the input .las files will not be removed and will remain in the output .las files. This is the default. Checked—The variable length records in the input .las files will be removed from the output .las files.	Boolean
Rearrange points (Optional)	Specifies whether points in the .las files will be rearranged. Unchecked—The order of the points in the .las files will not be rearranged. Checked—The points in the .las files will be rearranged. This is the default.	Boolean
Compute Statistics (Optional)	Specifies whether statistics will be computed for the .las files referenced by the LAS dataset. Computing statistics provides a spatial index for each .las file, which improves analysis and display performance. Statistics also enhance the filtering and symbology experience by limiting the display of LAS attributes, such as classification codes and return information, to values that are present in the .las file. Checked—Statistics will be computed. This is the default. Unchecked—Statistics will not be computed.	Boolean
Output LAS Dataset (Optional)	The output LAS dataset referencing the newly created .las files.	LAS Dataset
Compression (Optional)	Specifies whether the output .las file will be in a compressed format or the standard LAS format. Same As Input —The compression will be the same as the input. This option is only available when the input is a LAS dataset It is the default in that case. No Compression —The output will be in the standard LAS format (*.las). This is the default when the input is a point cloud scene layer. zLAS Compression —Output .las files will be compressed in the zLAS format.	String

Derived Output

Label	Explanation	Data Type
Output Folder	The folder to which the .las files will be written.	Folder

Python

arcpy.ddd.ExtractLas(in_las_dataset, target_folder, {extent}, {boundary}, {process_entire_files}, {name_suffix}, {remove_vlr}, {rearrange_points}, {compute_stats}, {out_las_dataset}, {compression})

Name	Explanation	Data Type
in_las_dataset	The LAS dataset or point cloud scene layer to process.	LAS Dataset Layer; Scene Service Layer; File
target_folder	The existing folder to which the output .las files will be written.	Folder
extent (Optional)	The extent of the data that will be evaluated. MAXOF—The maximum extent of all inputs will be used. MINOF—The minimum area common to all inputs will be used. DISPLAY—The extent is equal to the visible display. Layer name—The extent of the specified layer will be used. Extent object—The extent of the specified object will be used. Space delimited string of coordinates—The extent of the specified string will be used. Coordinates are expressed in the order of x-min, y-min, x-max, y-max.	Extent
boundary (Optional)	A polygon boundary that defines the area of the .las files that will be clipped.	Feature Layer
process_entire_files (Optional)	Specifies how the processing extent will be applied. PROCESS_EXTENT —Only LAS points that intersect the area of interest will be processed. This is the default. PROCESS_ENTIRE_FILES —If any portion of a .las file intersects the area of interest, all the points in that .las file, including those outside the area of interest, will be processed.	Boolean
name_suffix (Optional)	The text that will be appended to the name of each output .las file. Each file will inherit its base name from its source file, followed by the suffix specified in this parameter.	String
remove_vlr (Optional)	Specifies whether variable length records (VLRs) will be removed. Each .las file may potentially contain a set of VLRs that were added by the software that produced it. The meaning of these records is typically only known by the originating software. Unless the output LAS data will be processed by an application that understands this information, retaining the VLRs may not provide any value-added functionality. Removing the VLRs can potentially save significant disk space depending on their total size and the number of files containing them. MAINTAIN_VLR —Any data stored in the processed .las file's variable length records will not be removed and will remain in the extracted .las files. This is the default. REMOVE_VLR —The additional variable length records will be removed from the .las files.	Boolean
rearrange_points (Optional)	Specifies whether points in the .las files will be rearranged. MAINTAIN_POINTS —The order of the points in the .las files will not be rearranged. REARRANGE_POINTS —The points in the .las files will be rearranged. This is the default.	Boolean
compute_stats (Optional)	Specifies whether statistics will be computed for the .las files referenced by the LAS dataset. Computing statistics provides a spatial index for each .las file, which improves analysis and display performance. Statistics also enhance the filtering and symbology experience by limiting the display of LAS attributes, such as classification codes and return information, to values that are present in the .las file. COMPUTE_STATS —Statistics will be computed. This is the default. NO_COMPUTE_STATS —Statistics will not be computed.	Boolean
out_las_dataset (Optional)	The output LAS dataset referencing the newly created .las files.	LAS Dataset
compression (Optional)	Specifies whether the output .las file will be in a compressed format or the standard LAS format. SAME_AS_INPUT —The compression will be the same as the input. This option is only available when the input is a LAS dataset It is the default in that case. NO_COMPRESSION —The output will be in the standard LAS format (*.las). This is the default when the input is a point cloud scene layer. ZLAS —Output .las files will be compressed in the zLAS format.	String

Derived Output

Name	Explanation	Data Type
out_folder	The folder to which the .las files will be written.	Folder

Code sample

ExtractLas example 1 (Python window)

The following sample demonstrates the use of this tool in the Python window.

import arcpy
from arcpy import env

env.workspace = 'C:/data'
arcpy.ddd.ExtractLas('test.lasd', 'c:/lidar/subset', boundary='study_area.shp',
                     name_suffix='subset', remove_vlr=True, 
                     rearrange_points='REARRANGE_POINTS', 
                     out_las_dataset='extracted_lidar.lasd')

ExtractLas example 2 (stand-alone script)

The following sample demonstrates the use of this tool in a stand-alone Python script.

'''****************************************************************************
Name: Split Large LAS File
Description: Divides a large LAS file whose point distribution covers the full
             XY extent of the data into smaller files to optimize performance
             when reading lidar data.
****************************************************************************'''
# Import system modules
import arcpy
import tempfile
import math

in_las_file = arcpy.GetParameterAsText(0)
tile_width = arcpy.GetParameter(1) # double in LAS file's XY linear unit
tile_height = arcpy.GetParameter(2) # double in LAS file's XY linear unit
out_folder = arcpy.GetParameterAsText(3) # folder for LAS files
out_name_suffix = arcpy.GetParameterAsText(4) # basename for output files
out_lasd = arcpy.GetParameterAsText(5) # output LAS dataset


try:
    temp_lasd = arcpy.CreateUniqueName('temp.lasd', tempfile.gettempdir())
    arcpy.management.CreateLasDataset(in_las_file, temp_lasd, 
                                      compute_stats='COMPUTE_STATS')
    desc = arcpy.Describe(temp_lasd)
    total_columns = int(math.ceil(desc.extent.width/tile_width))
    total_rows = int(math.ceil(desc.extent.height/tile_height))
    digits = int(math.log10(max(cols, rows))) + 1
    for row in range(1, total_rows+1):
        yMin = desc.extent.YMin + tile_height*(row-1)
        yMax = desc.extent.YMin + tile_height*(row)
        for col in range (1, total_columns+1):
            xMin = desc.extent.XMin + tile_width*(col-1)
            xMax = desc.extent.XMax + tile_width*(col)
            name_suffix = '_{0}_{1}x{2}'.format(out_name_suffix, 
                                                str(row).zfill(digits), 
                                                str(col).zfill(digits))
            arcpy.ddd.ExtractLas(temp_lasd, out_folder, 
                                 arcpy.Extent(xMin, yMin, xMax, yMax),
                                 name_suffix=name_suffix, 
                                 rearrange_points='REARRANGE_POINTS',
                                 compute_stats='COMPUTE_STATS')
    arcpy.env.workspace = out_folder
    arcpy.management.CreateLasDataset(arcpy.ListFiles('*{0}*.las'.format(out_name_suffix)),
                                      out_lasd, compute_stats='COMPUTE_STATS',
                                      relative_paths='RELATIVE_PATHS')
except arcpy.ExecuteError:
    print(arcpy.GetMessages())

Environments

Current Workspace, Extent, Output Coordinate System, Geographic Transformations

Licensing information

• Basic: Requires 3D Analyst
• Standard: Requires 3D Analyst
• Advanced: Requires 3D Analyst