ENVISpatialSubsetPointCloud

This method creates a new ENVISpatialSubsetPointCloud object which is a spatial subset of an existing ENVIPointCloud object. This can be used with ENVI LiDAR processing ENVITasks to process only the specified subset of the data.

Note: The methods GetPointsInCircle, GetPointsInPolygon, GetPointsInRect, GetPointsInTile are not constrained by this sub-rectangle; they still return data from the full extents.

Example

; Create a headless instance

e = ENVI(/HEADLESS)

; Open a las file

file = FILEPATH('DataSample.las', ROOT_DIR=e.ROOT_DIR, $

SUBDIRECTORY = ['data','lidar'])

pointcloud = e.OpenPointCloud(file, $

PROJECT_URI=Filepath('DataSample', /TMP))

; Create a spatial subset of 100m x 100m for processing

subset = ENVISpatialSubsetPointCloud(pointcloud, [593741.00, 5289518.0, 593841.00, 5289618.0])

; Typical use case scenario would be to subset data for Feature Extraction processing

task = ENVITask('PointCloudFeatureExtraction')

task.INPUT_POINT_CLOUD = subset

task.DEM_GENERATE = 1

PRINT, 'Executing Point Cloud Feature Extraction Task'

task.Execute

; Get and print the generated products information

productsInfo = Task.OUTPUT_PRODUCTS_INFO

print, productsInfo

Syntax

Result = ENVISpatialSubsetPointCloud(PointCloud, SubRect [, ERROR=variable])

Return Value

This method returns an ENVISpatialSubsetPointCloud object that is a spatial subset of the original point cloud file.

Arguments

PointCloud

Specify the input ENVIPointCloud.

SubRect

Set this keyword to a four-element double-precision array expressing the spatial range of the required subset. The array is of the form [x1, y1, x2, y2], where:

x1 = the minimum X value to include in the subset
y1 = the minimum Y value to include in the subset
x2 = the maximum X value to include in the subset
y2 = the maximum Y value to include in the subset

These should be specified in the coordinate system used by the ENVIPointCloud object (see the ENVIPointCloud SPATIALREF property)

Note: To subset in the Z direction, use the GENERAL_CLIP_MIN_HEIGHT and GENERAL_CLIP_MAX_HEIGHT properties in the PointCloudFeatureExtraction task.

Methods

ENVISpatialSubsetPointCloud has the same methods as the ENVIPointCloud object, plus the following:

Dehydrate

Hydrate

Properties

ENVISpatialSubsetPointCloud has the same properties as the ENVIPointCloud object.

Keywords

ERROR

Set this keyword to a named variable that will contain any error message issued during execution of this routine. If no error occurs, the ERROR variable will be set to a null string (''). If an error occurs and the routine is a function, then the function result will be undefined.

When this keyword is not set and an error occurs, ENVI returns to the caller and execution halts. In this case, the error message is contained within !ERROR_STATE and can be caught using IDL's CATCH routine. See IDL Help for more information on !ERROR_STATE and CATCH.

See Manage Errors for more information on error handling in ENVI programming.

Version History

ENVI 5.3	Introduced
ENVI 5.3.2	Added Dehydrate method
ENVI 5.4	Added Hydrate method

API Version

4.2