Lab exercise 12, due right before the next class
GEO5083: Remote Sensing Image Processing and Analysis, UTSA
Student name: ______________
Hyperspectral image processing and analysis
This lab is to get familiar with some major processes for hyperspectral image processing and analysis.
Step 1. Preparation
The data you will use is the cup95eff.int located at c:/Program Files/ITT/IDL/IDL80/products/ENVI48/data/. This image is a spatial and spectral subset of an AVIRIS reflectance image. The atmospheric correction was done based on ATREM (ATmosphere REMoval Program) with the EFFORT correction (Empirical Flat Field Optimized Reflectance Transformation). When you open the image in ENVI, you will find the image format is BIL, which we mentioned before that BIL is a good format for retrieving both spectral and spatial information. The reflectance value here in the image is a scaled integer by multiplying 1000 (see Figure 1-left). We can easily convert the scaled integer into reflectance by dividing by 1000 (Figure 1-right) using the band math. Try use both equations of b1/1000 and float(b1)/1000.0, to see if you got different results or same results, explain why?
(EFFORT is a correction used to remove residual “saw-tooth” instrument (or calibration-introduced) noise and atmospheric effects from ATREM-calibrated AVIRIS data. It is a custom correction designed to improve overall quality of spectra. It provides the best reflectance spectra available from AVIRIS data)
Figure 1. Reflectance spectrum of scaled integer (left) and real reflectance (right)
Step 2. Endmembers selection and mapping
In this lab, you will use the "Spectral Hourglass Wizard" under Spectral menu. This wizard will lead you to do processes such as MNF, PPI, nDV, SA for endmembers selection, and then classify the image using any of or all three methods: SAM, MTMF, and Linear Spectral Unmixing. I suggest you to use both SAM and MTMF, if both give a good score for a pixel, then we define the pixel to the associated mineral. Please select the spectral library of usgs_min.sli from C:\Program Files\ITT\IDL\IDL80\products\envi48\spec_lib\usgs_min. (note: when you use the USGS spectral library, you are encouraged to read our recent paper in the reading materials)
Report details about parameters you selected, methods you used, results you found, and a final mineral compositions map either in ArcGIS or in ENVI. If using ENVI, you can also make a good map from the Display window: Click Overlay -> Grid Lines (see figure below). Then by clicking the Annotation -> Object, you will find all other map elements there.