Set LAS Class Codes Using Features (3D Analyst)

Summary

Classifies data points in LAS files referenced by a LAS dataset using point, line, and polygon features.

Usage

• LAS points can be classified into a number of categories that describe the material encountered by the lidar return, such as ground, building, or water. The American Society for Photogrammetry and Remote Sensing (ASPRS) defined the following class codes for LAS file versions 1.1, 1.2, and 1.3:

  Classification Value	Classification Type
  0	Never Classified
  1	Unassigned
  2	Ground
  3	Low Vegetation
  4	Medium Vegetation
  5	High Vegetation
  6	Building
  7	Noise
  8	Model Key
  9	Water
  10	Reserved for ASPRS Definition
  11	Reserved for ASPRS Definition
  12	Overlap
  13–31	Reserved for ASPRS Definition

  Note:

  While the LAS 1.0 specifications provide class codes ranging from 0 to 255, it does not have a standardized classification scheme. Any class codes used in 1.0 files would typically be defined by the data vendor and provided through auxiliary information.

• The LAS dataset layer can be used to filter LAS points by class code or return values. The layer can be created by using the Make LAS Dataset Layer tool, or by loading the LAS dataset in ArcMap or ArcScene and specifying the desired class codes and return values through the layer properties dialog box.

• LAS data points that fall within the 2-dimensional area of the buffer specified for the input features will be classified.

• Consider using the points obtained from Locate Outliers to classify LAS points as Noise.

Syntax

SetLasClassCodesUsingFeatures_3d (in_las_dataset, feature_class, {compute_stats})

Parameter	Explanation	Data Type
in_las_dataset	The input LAS dataset.	LAS Dataset Layer
feature_class [[features, buffer_distance, new_class, synthetic, key_point, withheld],...]	Specify one or more feature classes that will be used to define class code values for the lidar files referenced by a LAS dataset. Each feature will have the following options that can be specified: features—The feature layer or full path to the input feature class. buffer_distance—The selection tolerance used in determining which lidar points will be modified by the input features. new_class—The class code to be assigned to the lidar files that intersect with the features and the associated buffer distance. synthetic—Specifies whether to flag or remove a Synthetic designation, which implies that the point was not created with lidar, but an alternate technique (for example, digitized from photogrammetric stereo model). key_point—Specifies whether to flag or remove a Key Point designation for the data point. A model key point is typically treated as an anchor point that does not get removed by any thinning algorithm. withheld—Specifies whether to flag or remove a Withheld designation for the data point, which is generally used to signify erroneous data.	Value Table
compute_stats (Optional)	Specifies whether statistics should be computed for the LAS files referenced by the LAS dataset. The presence of statistics allows the LAS dataset layer's filtering and symbology options to only show LAS attribute values that exist in the LAS files. COMPUTE_STATS —Statistics will be computed. NO_COMPUTE_STATS —Statistics will not be computed. This is the default.	Boolean

Code Sample

SetLasClassCodesUsingFeatures example 1 (Python window)

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

import arcpy
from arcpy import env

arcpy.CheckOutExtension('3D')
env.workspace = 'C:/data'
arcpy.SetLasClassCodesUsingFeatures_3d("test.lasd", [["lake.shp 0 9"],
                                       ["outliers.shp", 5, "NO_CHANGE", 
                                        "NO_CHANGE", "NO_CHANGE", "SET"]], 
                                       "COMPUTE_STATS")

SetLasClassCodesUsingFeatures example 2 (stand-alone script)

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

'''**********************************************************************
Name: Assign Withheld Classification Flag to Outlier Points in LAS Files
Description: Uses Locate Outliers to identify points in LAS files that
             should be assigned the 'withheld' classification flag.
             Designed for use as a script tool.
**********************************************************************'''
# Import system modules
import arcpy
import exceptions, sys, traceback

try:
    arcpy.CheckOutExtension('3D')
    # Set Local Variables
    lasD = arcpy.GetParameterAsText(0)
    outliers = 'in_memory/outliers'
    # Execute LocateOutliers
    arcpy.ddd.LocateOutliers(lasD, outliers, 'APPLY_HARD_LIMIT', -10, 
                             350, 'APPLY_COMPARISON_FILTER', 1.2, 120, 
                             0.8, 8000)
    # Execute SetLasClassCodeUsingFeatures
    arcpy.ddd.SetLasClassCodesUsingFeatures(lasd, [["outliers.shp", 5, 
                                                    "NO_CHANGE", "NO_CHANGE",
                                                    "NO_CHANGE", "SET"]])
    arcpy.CheckInExtension('3D')
except arcpy.ExecuteError:
    print arcpy.GetMessages()
except:
    # Get the traceback object
    tb = sys.exc_info()[2]
    tbinfo = traceback.format_tb(tb)[0]
    # Concatenate error information into message string
    pymsg = 'PYTHON ERRORS:\nTraceback info:\n{0}\nError Info:\n{1}'\
          .format(tbinfo, str(sys.exc_info()[1]))
    msgs = 'ArcPy ERRORS:\n {0}\n'.format(arcpy.GetMessages(2))
    # Return python error messages for script tool or Python Window
    arcpy.AddError(pymsg)
    arcpy.AddError(msgs)

Environments

Current Workspace, Extent, Geographic Transformations

Licensing Information

ArcGIS for Desktop Basic: Requires 3D Analyst

ArcGIS for Desktop Standard: Requires 3D Analyst

ArcGIS for Desktop Advanced: Requires 3D Analyst