ENVIAgSpectralHotspotAnalysisTask

This task creates a spectral index image and runs hotspot analysis on it to look for areas that are statistically significant from surrounding areas. The resulting image shows the most significant features for the index.

ENVIAgSpectralHotspotAnalysisTask is a metatask that runs the following tasks:

ENVISpectralIndexTask
ENVIAgCalculateGetisOrdTask
ENVIAgHotspotColorSliceTask

This task is part of ENVI Crop Science, which requires a separate license and installation.

Example

This example creates a hotspot image that shows the relative health of alfalfa crops.

The source image consists of layer-stacked Sentinel-2A visible, near-infrared, and shortwave-infrared bands with a spatial resolution of 10 meters. The image is from eastern Idaho, USA. The accompanying region of interest (ROI) file encompasses alfalfa fields. It is used to mask out all non-alfalfa pixels from the source image. The masked raster is then used to calculate a Modified Simple Ratio index.

; Start the application

e = ENVI()

; Open an input file

File = Filepath('CircularFields_Sentinel2A.dat', $

  Subdir=['data', 'crop_science'], $

  Root_Dir=e.Root_Dir)

Raster = e.OpenRaster(File)

; Only process the actively growing fields

; using an ROI mask

ROIFile = Filepath('CircularFields_AlfalfaROI.xml', $

  Subdir=['data', 'crop_science'], $

  Root_Dir=e.Root_Dir)

ROI = e.OpenROI(ROIFile)

maskedRaster = ENVIROIMaskRaster(Raster, ROI)

; Get the task from the collection of tasks

Task = ENVITask('AgSpectralHotspotAnalysis')

; Define task inputs

Task.INPUT_RASTER = maskedRaster

Task.INDEX = 'Modified Simple Ratio'

Task.DISTANCE = 10 ; meters

; Run the task

Task.Execute

; Get the collection of data objects currently

; available in the Data Manager

DataColl = e.Data

; Add the output to the Data Manager

DataColl.Add, Task.OUTPUT_RASTER

; Display the result

View = e.GetView()

Layer = View.CreateLayer(Raster)

Layer2 = View.CreateLayer(Task.OUTPUT_RASTER)

View.Zoom, 0.75

Syntax

Result = ENVITask('AgSpectralHotspotAnalysis')

Input properties (Set, Get): INDEX, DISTANCE, INPUT_RASTER, OUTPUT_RASTER_URI

Output properties (Get only): OUTPUT_RASTER

Properties marked as "Init" are applied only during the initial creation of the object. Properties marked as "Set" are those that you can set to specific values after the object has been created. You can also retrieve their current values any time. Properties marked as "Get" are those whose values you can retrieve but not set.

Methods

This task inherits the following methods from ENVITask. See the ENVITask topic in ENVI Help.

AddParameter
Execute
Parameter
ParameterNames
RemoveParameters

Properties

This task inherits the following properties from ENVITask:

COMMUTE_ON_DOWNSAMPLE

COMMUTE_ON_SUBSET

DESCRIPTION

DISPLAY_NAME

NAME

REVISION

See the ENVITask topic in ENVI Help for details.

This task also contains the following properties:

DISTANCE (required)

Specify the radius of the area around each pixel used to calculate the local mean. If the input raster has a valid spatial reference, then the radius is measured in meters. Otherwise, it is measured in pixels.

INDEX (required)

Specify the spectral index on which to perform hotspot analysis. See the ENVISpectralIndexRaster topic in ENVI Help for a full list of spectral indices. You can run ENVIQuerySpectralIndicesTask to see what indices are available for your particular image.

INPUT_RASTER (required)

Specify a single-band input raster.

OUTPUT_RASTER

This is a reference to the output raster of filetype ENVI.

OUTPUT_RASTER_URI (optional)

Specify a string with the fully qualified filename and path of the output raster. If you do not specify this property, the output raster is only temporary. Once the raster has no remaining references, ENVI deletes the temporary file.

Version History

1.0	Introduced