HotspotAnalysis Task

AgHotspotAnalysis Task

This task runs hotspot analysis on a single-band raster to look for areas that are statistically significant from surrounding areas. The resulting image shows the most significant features for the image.

The difference between this task and ENVIAgSpectralHotspotAnalysis is that you can pass in any single-band raster, not just a spectral index.

AgHotspotAnalysis Task is a metatask that runs the following tasks:

This task requires a separate license for the ENVI Crop Science Module; contact your sales representative for more information.

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. You do not necessarily have to use a spectral index image; you can pass in any single-band raster.

; 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)

; Create a Modified Simple Ratio index

MSRImage = ENVISpectralIndexRaster(maskedRaster, 'MSR')

; Get the task from the collection of tasks

Task = ENVITask('AgHotspotAnalysis')

; Define task inputs

Task.INPUT_RASTER = MSRImage

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('AgHotspotAnalysis')

Input parameters (Set, Get): DISTANCE, INPUT_RASTER, OUTPUT_RASTER_URI

Output parameters (Get only): OUTPUT_RASTER

Parameters marked as "Set" are those that you can set to specific values. You can also retrieve their current values any time. Parameters marked as "Get" are those whose values you can retrieve but not set.

Input Parameters

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.

INPUT_RASTER (required)

Specify a single-band input raster.

OUTPUT_RASTER_URI (optional)

Specify a string with the fully qualified filename and path of the associated OUTPUT_RASTER.

If you do not specify this parameter, or set it to an exclamation symbol (!), ENVI creates a temporary file.
If you set it to the hash symbol (#), ENVI creates a file in the temporary directory, but this file will not be deleted when ENVI closes.