Use the Spectral Hourglass Wizard to guide you step-by-step through the ENVI hourglass processing flow to find and map image spectral endmembers from hyperspectral or multispectral data. The Wizard displays detailed instructions and useful information for each function.

From the Toolbox, select Spectral > Spectral Unmixing > Spectral Hourglass Wizard to start the workflow. The following chart shows the processing flow:

The hourglass processing flow uses the spectrally over-determined nature of hyperspectral data to find the most spectrally pure, or spectrally unique, pixels (called endmembers) within the dataset and to map their locations and sub-pixel abundances. This processing flow begins with reflectance or radiance input data. You can spectrally and spatially subset the data, visualize the data in n-D space and cluster the purest pixels into endmembers, and optionally supply your own endmembers. You can map the distribution and abundance of the endmembers, use ENVI’s Spectral Analyst to identify the endmembers, and review the mapping results.

The name of the corresponding ENVI function appears at the top of the panel during each step. ENVI adds the resulting output to the Layer Manager. Various plots appear throughout the processing flow to help assess results as you proceed.

After starting the Spectral Hourglass Wizard, refer to the following sections for help:

• Wizard Basics
• Input/Output File Selection
• Minimum Noise Transform
• Data Dimensionality and Spatial Coherence
• Derive Endmembers from the Input Image
• Perform Classification, MTMF, and Spectral Unmixing
• Summary Report