HYPEX Demo Information




Version 1.0   -   May 1996







Photon Research Associates, Inc.
5720 Oberlin Drive
San Diego, California 92121-1723

NOTIFICATION OF COPYRIGHT

Copyright 1996 by Photon Research Associates, Inc., All Rights Reserved
This software program package is a proprietary product of Photon Research Associates, Inc. (PRA) and is protected by copyright laws and international treaty. No portion of this software package may be copied or modified without the consent of PRA except to make copies for backup purposes only.

TABLE OF CONTENTS

1.0 - CDROM Information

2.0 - Demo Databases

1.0 CDROM Information

The "hypex.run" file on this CDROM executes an X-based interface that provides point-and-click access to fifteen demonstrations presented using the Spectral Image Display tool, SID. In each of these "demos" SID is used to combine model-predicted spectral radiance data generated by the prototype HYPEX product with AVIRIS scenes collected over five landscapes. Critical to the success of the model-supported exploitation concepts presented here, is a requirement for data from an instrument that is well calibrated and characterized, such as AVIRIS. The AVIRIS data sets included on this Demo CD were acquired from the AVIRIS Project Office at JPL. Documents defining the AVIRIS Project, Instrument, and Data Processing Facility can be found at ftp://ophelia.jpl.nasa.gov/pub/docs/html/aboutAV.htm

The demonstrations contained on this Demo CD illustrate the capability of SID to explore hyperspectral imagery through sequential viewing of all bands (spectral movie); plot computed surface radiance and reflectance, and at-sensor radiance; and directly compare measured scene radiance values to predicted material radiance values derived from a reflectance library. Reflectance/radiance plots are linked with the image display allowing the user to query both the image and plotted values. The user can customize the viewer through image magnification/reduction and plot scaling, and can save ASCII "plot" files for selected pixels.

To launch the Demo GUI type "hypex.run" at the command line, or double click the "hypex.run" icon in the opened /CDROM folder. To select an AVIRIS scene of interest, click the appropriately labeled button on the interface. To select a "demo", click on one of the titles presented in the Demo Browser and then click the launch button. Pressing the help button in the "Demo Browser" brings up Mosaic with a hyper-text document containing information about AVIRIS and modeled data bases.

2.0 Demo Databases

Fifteen demos are included on the CDROM, three for each of five AVIRIS data sets: San Pablo, Cuprite, Rogers Dry Lake, Jasper Ridge, and Moffett Field. For each of the AVIRIS scenes, except San Pablo, three simulated radiative environments were computed using the Moderate Resolution Atmospheric Radiative Transfer (MOSART) code.

Three Model Atmospheres representing the range of latitudinal conditions for each site were used to drive the atmospheric radiative transfer calculations. These Model Atmospheres are: the U.S. Standard 1976 (s76), Sub-Arctic Summer (sas), and Sub-Tropical Summer (sts). Selected surface reflectance spectra were extracted from a library of material optical properties, combined with radiative environment data from MOSART, and convolved with the instrument spectral response functions to produce scene-specific simulated spectral radiance. On the Demo CD, these data are typically stored in the "spcalc" sub-directory found in each scene data base directory.

Thus, for each material and Model Atmosphere, these modeled spectral radiance data sets are specific to the conditions at the site (altitude, illumination geometry, etc.), and the altitude, viewing geometry, and spectral characteristics of the sensor. By running each "demo" the generated data sets permit the user to compare the effects of changes in a suite of atmospheric parameters represented by each Model Atmosphere on the reflectance properties of the scene and individual materials. The Sub-Tropical Summer Model Atmosphere demonstrates the impact of excessive atmospheric water vapor content on the calculation of reflectance, while the Sub-Arctic Summer Model Atmosphere provides a reference atmosphere that is too dry.

The three San Pablo scene "demos" were developed using a Mid-Latitude Spring Model Atmosphere "customized" by incorporating surface observations of pressure, temperature, and humidity into the MOSART input stream. The two excursions presented as the second and third San Pablo "demos" are included to illustrate the variability of the spectral signature at the resolution of the atmospheric simulation, and to punctuate the limited information contained within Landsat Thematic Mapper (TM) bands.

2.1 San Pablo

The San Pablo AVIRIS scene acquired in 1994 includes a portion of eastern San Pablo Bay, located north of San Francisco Bay. The small community of Crockett, an oil refinery and oil storage facility, and undeveloped areas are present in the scene. While viewing the "spectral" movie in SID note how the various bands highlight and/or separate many of the urban, natural, and water features present in the scene. The San Pablo Scene document contains an annotated image that identifies a few features in the scene.

The incorporation of both measured and modeled data in SID allows the user to assess the accuracy of the atmospheric state and the illumination and viewing geometry parameters input to the atmospheric and spectral radiance simulation models. It also provides the user with the data necessary to determine the fidelity of the spectral and radiometric characterization/calibration associated with the measured data.

By comparing the computed Black Body spectral radiance (yellow) with the spectral signature of the Wetland region, the darkest object in the scene, the user can visually assess the accuracy of the model-computed path radiance term. Similarly, comparing the modeled White Body (green) with the brightest object in the scene (Bright Tank), the user has an upper bound for the spectral radiance of non-glint targets. (Note: The saw-toothed spectra for the Bright Tank pixels indicate the presence of an "error" in the original measurement or downstream processing.) Plotting the spectra for the Gas Flares (identified as bright point-like features in bands 220-224), the White Body spectral radiance curve is nearly exceeded due to the thermal signature of these objects.

When plotting the Reflectance of objects in the scene, it is interesting to note that the calculated reflectance for the large asphalt region is spectrally "flat", as expected, while the large "white" oil storage tanks do not have a constant reflectance even in the visible and NIR. In fact, several tanks have significantly different spectra (absorption at .54 um), but appear "similar" to the eye. As one would expect, the spectra of the sediment-rich water peaks in the visible, the dark wetland area is spectrally "flat", while the surrounding region has a signature that is characteristic of vegetation.

The three "demos" for San Pablo are: 

     Customized Mid-Latitude Spring Model Atmosphere
     High Resolution (2 wavenumber) Spectral Excursion
     Landsat Thematic Mapper Spectral Comparison

A Normalized Difference Vegetation Index (NDVI) image, and the first four principle component images (PC 1-4) are included in the "spectral" movie option in SID. For more information regarding the AVIRIS scene and the parameters used for the atmospheric calculations, see San Pablo Scene.

2.2 Cuprite

The Cuprite scene was collected in early June 1992 over the Nevada desert near Goldfield and Tonopah. The scene contains a mixture of rock, soil, and sand. The SWIR bands of the AVIRIS instrument are particularly useful for separating differences in the rock/minerals present. By comparing the observed AVIRIS signature (white) with the modeled White Body and Black Body spectral radiance curves (green and yellow) in the SID View one is able to isolate the mineral absorption feature present at AVIRIS band 191 (2.17 um) from the numerous atmospheric absorption features present in the data. Employing the atmospheric compensation algorithm in SID, the mineral absorption feature present in AVIRIS band 191 (2.17 um) is easily detected in the SID Plot Window.

The three "demos" for Cuprite are: 

     U.S. Standard 1976 Model Atmosphere
     Sub-Arctic Summer Model Atmosphere
     Sub-Tropical Summer Model Atmosphere

The "spectral" movie includes the first four principle component images, and NDVI. For more information regarding the AVIRIS scene and the parameters used for the atmospheric calculations see Cuprite Scene.

2.3 Rogers Dry Lake

The Rogers Dry Lake is located on Edwards Air Force Base in California's western Mojave Desert north of Los Angeles. The scene collected in late May 1992 primarily covers the dry lakebed with some of the base facilities on the western edge (left) of the scene. Several cultural features are present in the lakebed, e.g., compass rose and runways, whose visibility is enhanced or muted over the spectral range of the instrument. As in the San Pablo Scene, the asphalt and concrete features are spectrally "flat" when viewed as Reflectance Plots. The "spectral" movie emphasizes variation in the soil signature across the lakebed.

The three Rogers Dry Lake "demos" are: 

     U.S. Standard 1976 Model Atmosphere
     Sub-Arctic Summer Model Atmosphere
     Sub-Tropical Summer Model Atmosphere

NDVI and principle component images 1-4 are included in the spectral movie option. For more information regarding the AVIRIS scene and the parameters used for the atmospheric calculations, see Rogers Dry Lake Scene.

2.4 Jasper Ridge

Data for Jasper Ridge near the Stanford University campus were acquired in early June 1992. The scene contains largely natural vegetation typical of coastal mountains/hill in California. Prominently visible in the scene is the Stanford linear accelerator. Surrounding the accelerator the landscape appears to be covered with dry grass whose reflectance signature is missing the characteristic chlorophyll absorption feature at .66 um present in the spectra of the adjoining woodlands and irrigated lawns.

The three Jasper Ridge "demos" are: 

     U.S. Standard 1976 Model Atmosphere
     Sub-Arctic Summer Model Atmosphere
     Sub-Tropical Summer Model Atmosphere

NDVI and principle component images 1-4 are included in the spectral movie option. For more information regarding the AVIRIS scene and the parameters used for the atmospheric calculations, see Jasper Ridge Scene.

2.5 Moffett Field

Located near the Jasper Ridge scene and acquired on the same June 1992 date is the Moffett Field scene. Land cover in the scene is predominately related to the air field and the surrounding urban area. The air field is shared with NASA Ames Research Center, and is located adjacent to southern San Francisco Bay. At the end of the runway a wetland and a portion of a salt evaporation pond are visible within the scene. It is interesting to compare the Reflectance spectra of the bay, pond and wetland. As with the other scenes, the asphalt and concrete Reflectance Plots are spectrally "flat". In contrast, many of the bright-roofed (white) buildings contained in the scene have an interesting "step" in their reflectance spectra near 2.2 um.

The three "demos" for Moffett Field are: 

     U.S. Standard 1976 Model Atmosphere
     Sub-Arctic Summer Model Atmosphere
     Sub-Tropical Summer Model Atmosphere

NDVI and principle component images 1-4 are included in the spectral movie option. For more information regarding the AVIRIS scene and the parameters used for the atmospheric calculations, see Moffett Field Scene.