Use the SAM Target Finder with BandMax Workflow to find targets in hyperspectral images using a SAM classification and (optionally) the BandMax algorithm. The BandMax algorithm increases classification accuracy by determining an optimal subset of bands to help you separate your targets from known background materials.
See the following for help on a particular step of the workflow:
Workflow Tips
This workflow is not “modal,” meaning it will not block you from using other ENVI tools or working with additional data. This is useful in that the workflow will not prevent you from doing multiple things at a time. However, be aware that if you close all of your files in the middle of the workflow process, you might not be able to continue the workflow and will need to start over.
Navigating Workflow Steps
The number of steps provided in the workflow will depend on the input image data. For example, not all images will contain the data needed for every step; therefore, some steps will be skipped automatically.
Some steps can be optional; in those cases, the Perform this step radio button is selected by default. To skip that step and go to the next step in the workflow, select the Skip this step radio button, then click Next.
The timeline at the bottom of the workflow will display the order of steps available for the workflow and your data, and the title of your current location in the workflow will flash. The title is also an active link that you can click, to jump backward or forward to a desired step in the workflow.
Preview/Display Result
Some workflow steps provide options to preview the settings and/or to display the processed result.
- Enable the Preview check box to see a preview of the settings before you click OK and process the data. The preview is calculated only on the area in the view and uses the resolution level at which you are viewing the image. See Preview for details on the results. To preview a different area in your image, pan and zoom to the area of interest and re-enable the Preview option.
- Enable the Display result check box to display the raster in the view when processing is complete.
Open Workflow in Modeler
On the last step of the workflow, the Open Workflow in Modeler link will take your full workflow - the exact data, choices, and parameter values that you selected - and create a Model that can be manipulated in the ENVI Modeler. For example, you could create a Model to perform batch processing with multiple similar input datasets.
Select Data
- From the Toolbox, select Workflows > SAM Target Finder with BandMax Workflow. The Select Data panel appears.
- Select an input file and perform optional spatial and spectral subsetting and/or masking, then click OK.
- Click Next.
Select Signatures
The Select Signatures panel appears after you select the input raster.
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Right-click on the following options to select the spectral signatures to import:
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Target: Uses target signatures from a selected spectral library to find objects. Target spectral signatures are required for the SAM Target Finder algorithm.
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Background: Uses background signatures to find objects. Background spectral signatures are required for the SAM Target Finder with BandMax algorithms. If you do not specify background signatures, only the SAM Target Finder algorithm will be used.
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Click Next.
BandMax
The BandMax panel appears if you specified background spectral signatures in the Select Signatures panel. If you did not specify background signatures, the SAM Classification panel appears (described next).
A plot on the BandMax panel plots the wavelengths of the bands with a significance value greater than or equal to the default significance threshold. BandMax performs significance computations to determine a band significance value for each band. Background data is rejected by determining a subset of spectral image bands that are useful in distinguishing between target and background spectra. The significance value is unitless and ranges from 0 to 1. A list of bands is then derived by comparing the band significance values to the threshold, and the resulting band subset maximizes the contrast between selected target and backgrounds. The default threshold value is calculated to select 25% of the input bands, but not less than six bands.
Reference:
The BandMax algorithm was developed by the Galileo Group, Inc. The process is based on the United States patent application titled "Spectral image processing system and method for target detection and identification."
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To change the Threshold or Number of Bands values by moving the slider bar or changing the value in the field provided. The subset from these settings is used as input to the SAM analysis to reduce processing time, and to increase accuracy in processing the data to help discriminate targets from background clutter.
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Click Next.
Threshold
The SAM Classification panel appears, with a suggested classification threshold value applied to the image. The value shows the data range of the SAM analysis result.
- To change the threshold value, drag the slider bar or type the desired value in the text box. Regions in the image that are black will be masked as areas of no interest.
- Click Next.
Smooth
The Smooth panel appears. Use this panel to set parameters for aggregating and smoothing on a class raster.
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In the Minimum Pixels field, set the aggregate minimum size for pixels. Regions this size or larger will be aggregated into a larger, adjacent region.
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Set the smooth Kernel Size, using an odd number.
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Click Next.
Export Results
Select the products to create in the Export Results panel.
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Enable check boxes for the desired exports. A Filename field will appear for the exports you enable; enter a filename and location for each. The options are:
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Click Finish.
See Also
Target Detection