AIRMISR_BARTLETT_2003 Data Set Readme -------------------------------------------------------------------------------- 1.0 Introduction This file contains information about AirMISR data taken during a flight over the Bartlett Experimental Forest, New Hampshire, USA, target as part of the AirMISR deployments from the Wallops Flight Facility during the August 2003 campaign. The Terrestrial Ecology Program at NASA Headquarters funded the AirMISR data acquisition and processing. This particular flight took place on August 24, 2003. The Jet Propulsion Laboratory (JPL) in Pasadena, California provided these data. This data set is available through the Langley Atmospheric Science Data Center as: AIRMISR_BARTLETT_2003 There were a total of two runs during this flight. A run comprises data collected from nine view angles acquired on a fixed flight azimuth angle. Each data file from one run contains either: a) Level 1B1 Radiometric product from one of the 9 camera angles or b) Level 1B2 Georectified radiance product from one of the 9 camera angles. Browse images in PNG format are available for the Level 1B1 product and browse images in JPEG format are available for the Level 1B2 product. Additional information about AirMISR can be obtained at the following location: http://www-misr.jpl.nasa.gov/mission/air.html Additional information about tools to read and view AirMISR data can be obtained at the following location: http://eosweb.larc.nasa.gov/PRODOCS/misr/misr_tools.html This Readme file includes the following sections: Section 2.0 - Data Set Description Section 3.0 - Data Format and Packaging Section 4.0 - Science Parameter Information Section 5.0 - Description of Sample Read Software Section 6.0 - Implementing Sample Read Software Section 7.0 - Sample Output Section 8.0 - Additional Information If there are questions about using the AIRMISR_BARTLETT_2003 sample read software, please contact the Langley ASDC User and Data Services office at: Atmospheric Science Data Center NASA Langley Research Center Mail Stop 157D Hampton, VA 23681-2199 USA E-Mail: support-asdc@earthdata.nasa.gov Phone: (757)864-8656 FAX: (757)864-8807 2.0 Data Set Information This flight over the Bartlett Experimental Forest, New Hampshire, was one of several AirMISR deployments from the Wallops Flight Facility to acquire data over East Coast forests during the three-week period from August 11 through September 3, 2003. The AirMISR data were acquired in conjunction with data from the AVIRIS instrument in support of the combined carbon chemistry and canopy structure studies by Scott Ollinger and Rob Braswell of the University of New Hampshire. The Terrestrial Ecology Program at NASA Headquarters funded their work. The Airborne Multi-angle Imaging SpectroRadiometer (AirMISR) is an airborne instrument for obtaining multi-angle imagery similar to that of the satellite- borne Multi-angle Imaging SpectroRadiometer (MISR) instrument, which is designed to contribute to studies of the Earth’s ecology and climate. AirMISR flies on the NASA ER-2 aircraft. The Jet Propulsion Laboratory in Pasadena, California built the instrument for NASA. Unlike the spaceborne MISR instrument, which has nine cameras oriented at various angles, AirMISR utilizes a single camera in a pivoting gimbal mount. In general, a data run by the ER-2 aircraft is divided into nine segments, each with the camera positioned to a particular MISR look angle. The gimbal rotates between successive flight segments, such that each segment acquires data over the same area on the ground as the previous segment. This process is repeated until all nine angles of the target area are collected. The swath width, which varies from 11 km in the nadir to 32 km at the most oblique angle, is governed by the camera's instantaneous field-of-view of 7 meters cross-track x 6 meters along-track in the nadir view and 21 meters x 55 meters at the most oblique angle. The along-track image length at each angle is dictated by the timing required to obtain overlap imagery at all angles, and varies from about 9 km in the nadir to 26 km at the most oblique angle. Thus, the nadir image dictates the area of overlap that is obtained from all nine angles. The use of a single camera to provide coverage at all nine angles is possible because AirMISR is not attempting to obtain continuous, global coverage, as is the case from the spaceborne MISR. This approach ensures identical calibration at all angles, a useful feature in utilizing the instrument as part of the MISR calibration. The 9 camera viewing angles are: 0 degrees or nadir 26.1 degrees, fore and aft 45.6 degrees, fore and aft 60.0 degrees, fore and aft 70.5 degrees, fore and aft For each of the camera angles, images are obtained at 4 spectral bands. The spectral bands can be used to identify vegetation and aerosols, estimate surface reflectance and ocean color studies. The center wavelengths of the 4 spectral bands are: 443 nanometers, blue 555 nanometers, green 670 nanometers, red 865 nanometers, near-infrared Two types of AirMISR data products are available for this data set through the Langley Atmospheric Science Data Center. These are 1) the Level 1 Radiometric product (L1B1), and 2) the Level 1 Georectified radiance product (L1B2). The Level 1 Radiometric product contains data that are scaled to convert the digital output of the cameras to radiances and are conditioned to remove instrument-dependent effects. Additionally, all radiances are adjusted to remove slight spectral sensitivity differences among the detector elements of each spectral band. These data have a 7-meter spatial resolution at nadir and around 30-meter at the most oblique 70.5 degree angles. The Level 1 Georectified radiance product contains the Level 1 radiometric product resampled to a 27.5 meter spatial resolution and mapped into a standard Universal Transverse Mercator (UTM) map projection. Initially the data are registered to each camera angle and to the ground. This processing is necessary because the nine views of each point on the ground are not acquired simultaneously. Once the map grid center points are located in the AirMISR imagery through the process of georectification, a radiance value obtained from the surrounding AirMISR pixels is assigned to that map grid center. Bilinear interpolation is used as the basis for computing the new radiance. A UTM grid point falling somewhere in the image data will have up to 4 surrounding points. The bilinear interpolated value is obtained using the fractional distance of the interpolation point in the cross-track direction and the fractional distance in the along-track direction. 2.1 Data Quality 2.1.1 Radiometric Data Quality The science flights made by AirMISR over the Bartlett Experimental Forest, New Hampshire, target on 08/24/2003 were successful. The camera successfully slewed to all nine angle positions for two runs. The radiometric accuracy and signal-to-noise during this mission was as good as the Science Team has reported in the literature. Individual product files contain metadata identifying dropped/corrupt lines, saturated pixels and related image quality parameters. The radiometric calibration of AirMISR was done using the same procedures as used to calibrate the MISR cameras; the reported radiometric calibration uncertainties are therefore the same as reported for MISR. (The exception is the camera-to-camera uncertainty, which is believed to be smaller for AirMISR, as the aircraft instrument consists of one gimballed camera). Thus, it is believed that the radiometric uncertainties are small, and the camera signal-to-noise is high. The values quoted for the systematic component of the radiometric uncertainty, based on vicarious calibration of the instrument, in fractional units, are: abs_sys_error 0.030 cam_sys_error 0.000 band_sys_error 0.010 pixel_sys_error 0.005 That is, the systematic component of the absolute, camera-to-camera, band-to- band, and pixel-to-pixel uncertainties are given above. The pixel-to-pixel uncertainty is large enough to cause some visible striping in the imagery where the scene contrast is low and the image display is stretched to highlight small radiometric differences. These systematic components are combined with signal-to-noise (SNR) to determine the total error uncertainties. As SNR is signal dependent, the uncertainties are likewise signal dependent. SNR, at two radiance input levels, are as follows: SNR(equivalent-reflectance=1.0) ~ 1000 SNR(equivalent-reflectance=0.05) ~ 200 Using these, the total radiometric uncertainties can be determined: abs_total_error=sqrt(abs_sys_error2+(1/SNR)2) cam_total_error=sqrt(2)/SNR band_total_error=sqrt(2)*sqrt(band_sys_error2+(1/SNR)2) pixel_total_error=sqrt(2)*sqrt(pixel_sys_error2+(1/SNR)2) References on the radiometric calibration of AirMISR and MISR are listed in Section 8.0. Additional references are available from the MISR web site http://www-misr.jpl.nasa.gov 2.1.2 Georectified Radiance Data Quality Geometric calibration is performed prior to orthorectification to the UTM map projection grid. The orthorectified Landsat TM scenes (path 011 row 029 ) obtained through ESE Scientific Data Purchase are used to collect a set of ground control points in order to remove static errors in the camera pointing and airplane position and assure absolute geolocation accuracy in particular for nadir images from both runs. An automated tie points identification and bundle adjustment is used to improve coregistration accuracy between off-nadir and nadir imagery. Using calibration results, geolocation and coregistration errors of about 1000 meters for the nadir view to up to 6000 meters for the most oblique views are reduced down to an average of about 60 meters for both absolute geolocation and coregistration out of nine view angles. Errors associated with the D camera view angles are somewhat larger, about 150 meters on average, due to the inability to identify a sufficient number of reliable ground control points in the imagery acquired at those oblique angles. 2.2 Science Point of Contact John Martonchick JPL MS 169-237 4800 Oak Grove Dr. Pasadena, CA 91109-8099 Phone: 818-354-2207 Fax: 818-393-4619 E-mail: John.Martonchick@jpl.nasa.gov 3.0 Data Format and Packaging 3.1 Data Format The L1B1 data are in HDF format. The L1B2 data are in HDF-EOS format, which can be read as HDF format. Further information about HDF-EOS (Hierarchical Data Format - Earth Observing System) Standards and Tools can be found at the HDF-EOS web site, http://hdfeos.org/ Information regarding HDF format is available at the following web sites: http://hdf.ncsa.uiuc.edu/ http://eosweb.larc.nasa.gov/HBDOCS/hdf.html 3.2 Data File Naming Convention AirMISR data files are named in the following manner, where all elements within the <> symbols are variable. AIRMISR_RP___F_.hdf AIRMISR_GP___F_.hdf AIRMISR_RP: native HDF file containing AirMISR Level 1B1 radiometrically calibrated product that is processed to sensor units, but not geolocated. AIRMISR_GP: HDF-EOS file containing AirMISR Level 1B2 geometrically calibrated, geolocated data derived from L1B1 data : date and time in UTC computed from ER-2 navigation for image mid-point in the downtrack direction. : AirMISR camera angles, DF - fore, 70.5 degrees viewing angle CF - fore, 60.0 degrees viewing angle BF - fore, 45.6 degrees viewing angle AF - fore, 26.1 degrees viewing angle AN - nadir, 0 degrees viewing angle AA - aft, 26.1 degrees viewing angle BA - aft, 45.6 degrees viewing angle CA - aft, 60.0 degrees viewing angle DA - aft, 70.5 degrees viewing angle : defines which product format was used in creating the product. The format version refers to the entire system used to generate products, so L1B1 and L1B2 format versions will change together. Files processed after December 20, 2002 have a format version of F04. The format version for files processed up to 5/31/2001 is F01. The F02 format was used between these two dates. F03 was not used for publicly released files. Note that this refers to the processing date, not the flight date. : defines the content of a file. The value is incremented every time the data are reprocessed. The value is reset to 01 when a new format version is created. Example file names: AIRMISR_RP_030828_162822_BA_F04_01.hdf AirMISR Level 1B1 Radiometric product taken on August 28, 2003 with the image mid-point at 16:28:22 UTC. The viewing angle is 45.6 deg. aft, the format version is 04 and the file version is 01. AIRMISR_GP_030828_160002_BF_F04_01.hdf AirMISR Level 1B2 Georectified radiance product taken on August 28, 2003 with the image mid-point at 16:00:02 UTC. Data is for viewing angle 45.6 deg. fore, the format version is 04 and the file version is 01. 3.3 Image Naming Convention The "RP" (L1B1) data files have associated PNG images. The images are named using the same naming convention as the data files with the addition of the image size and spectral band. AIRMISR_RP___F_. ..png : blue, green, red and near-infrared spectral bands. : thumb - 100 x 100 pixels browse - 640 x 480 pixels full – size varies with camera The "GP" files have associated JPEG images also with a naming convention similar to that of the data file name. AIRMISR_GP___F_.jpg The pixel dimensions vary with the size of the data area, which depends on the camera angle. Example image names: AIRMISR_RP_030828_160144_AN_F04_01.red.thumb.png AirMISR Level 1B1 Radiometric browse product taken on August 28, 2003 with the image mid-point at 16:01:44 UTC. The viewing angle is 0.0 degrees (nadir), format version 04, file version 01, red spectral band centered at 670 nanometers, thumbnail size, in the PNG format. AIRMISR_GP_030828_160055_AF_F04_01.jpg AirMISR Level 1B2 Georectified radiance browse product taken on August 28, 2003 with the image mid-point at 16:00:55 UTC. The viewing angle is 26.1 degrees forward of nadir, format version 04, file version 01 in the JPEG format. 4.0 Science Parameter Information 4.1 L1B2 Grid Field Parameters For detailed information regarding file contents, please obtain the AirMISR Data Products Specifications (DPS) document at the following URL: http://eosweb.larc.nasa.gov/PRODOCS/airmisr/table_airmisr.html -------------------------------------------------------------------------------- Field Data Type Fill Value Units Description -------------------------------------------------------------------------------- Terrain Blue uint16 65535 unitless scaled radiance Terrain Blue DQI uint8 255 unitless data quality index Terrain Green uint16 65535 unitless scaled radiance Terrain Green DQI uint8 255 unitless data quality index Terrain Red uint16 65535 unitless scaled radiance Terrain Red DQI uint8 255 unitless data quality index Terrain Infrared uint16 65535 unitless scaled radiance Terrain Infrared DQI uint8 255 unitless data quality index Ellipsoid Blue uint16 65535 unitless scaled radiance Ellipsoid Blue uint8 255 unitless data quality index Ellipsoid Green uint16 65535 unitless scaled radiance Ellipsoid Green DQI uint8 255 unitless data quality index Ellipsoid Red uint16 65535 unitless scaled radiance Ellipsoid Red DQI uint8 255 unitless data quality index Ellipsoid Infrared uint16 65535 unitless scaled radiance Ellipsoid Infrared DQI uint8 255 unitless data quality index Sun Azimuth float32 -9.999E+03 degrees solar azimuth angle Sun Zenith float32 -9.999E+03 degrees solar zenith angle View Azimuth float32 -9.999E+03 degrees viewing azimuth angle View Zenith float32 -9.999E+03 degrees viewing zenith angle Elevation int16 -32768 meters surface elevation Elevation uncertainty int16 -32768 meters RMS of uncertainty -------------------------------------------------------------------------------- The Terrain and Ellipsoid fields listed above refer to the two projections used in georectifying the data. The scaled radiance is the total-band, standardized spectral response weighted. To compute actual radiance, multiply these values by their corresponding scale factor listed in the metadata below. The sample read software, described in Sections 5 to 7, performs these computations. A DQI value of 0 indicates a good data value in the corresponding radiance file and a value of 255 indicates the radiance data value is set to the fill value. 4.2 L1B2 Grid Attribute (Metadata) Parameters -------------------------------------------------------------------------------- Field Data Type Units Description -------------------------------------------------------------------------------- UL Corner float64 degrees upper left corner of data region (lat/lon) LR Corner float64 degrees lower right corner of data region (lat/lon) Rad_scale_factor float64 Wm-2um-1sr-1 scaled radiance conversion factor; 4 values: 1=blue;2=green;3=red;4=nir std_inband_solar_wgted_height float64 Wm-2um-1 solar irradiances, standardized response weighted; 4 values: 1=blue;2=green;3=red;4=nir std_inband_solar_wgted_center_wav float64 nm center wavelength, solar and in-band standardized response weighted; 4 values: 1=blue;2=green;3=red;4=nir std_inband_solar_wgted_width float64 nm bandwidth, solar and in-band standardized response weighted; 4 values: 1=blue;2=green;3=red;4=nir std_solar_wgted_height float64 Wm-2um-1 solar irradiances, standardized response weighted; 4 values: 1=blue;2=green;3=red;4=nir std_solar_wgted_center_wav float64 nm center wavelength, solar and (nm) standardized response weighted; 4 values: 1=blue;2=green;3=red;4=nir std_solar_wgted_width float64 nm bandwidth, solar and standardized response weighted; 4 values: 1=blue;2=green;3=red;4=nir band_wgted_max_rad float64 Wm-2um-1sr-1 band weighted maximum radiance; 4 values: 1=blue;2=green;3=red;4=nir Minimum_image_time char8 UTC image start time Maximum_image_time char8 UTC image end time Sun_distance float64 Astronomical Earth Sun distance units 5.0 Description of Sample Read Software Currently, there is one sample read program which reads the Level 1B2 Georectified radiance product ("GP" files), read_airmisr.pro. This software does not read the Level 1B1 Radiometric product ("RP" files). Information about tools that read and view AirMISR data can be obtained at the following location: http://eosweb.larc.nasa.gov/PRODOCS/airmisr/table_airmisr.html The read software is written in the ITT Visual Information Solutions IDL programming language. It can be run either with a licensed version of the IDL package or by using the IDL Virtual Machine application that can be obtained from ITT Visual Information Solutions free of charge as described in section 6.2. The software was tested on the following computers and operating systems: Computer Operating System IDL Version ---------------- ---------------- ----------- Sun Sparc Solaris 2.8 6.0 IBM PC Windows 2000 6.0 Note: This program uses some features that require IDL version 6.0. A version of the read_airmisr software that runs in IDL versions 5.3-5.6 that will read the Level 1B2 data files is available from the AirMISR tools page whose URL is listed above. This version does not run in the IDL Virtual Machine. The read_airmisr program is written as an example of how to read the AirMISR Georectified radiance product or the land surface product. For the radiance product, actual radiances are computed from the scaled radiance values and the scale factor. As delivered, it prompts the user to select an input filename and parameters to output. It reads in the selected fields from the file, computes radiance if selected and writes the selections to the output file in ASCII format. The output file is given the same name as the selected AirMISR file, but the ".hdf" file suffix is replaced with "_output.txt". It is written to the current default directory. 6.0 Implementing the Sample Read Software 6.1 Extract the files from the delivery package The read software is packaged as a tar file, read_airmisr.tar, which can be opened on both Unix and Windows systems. The tar file contains the read_airmisr.pro source code file, the read_airmisr.sav executable file, and a bitmap logo file, read_airmisr.bmp. On Unix systems, use the command tar read_airmisr.tar to extract the files into a directory on your system. On Windows systems, a package such as WinZip for extracting from zipped files will also extract from tar files. Use the package's extract capability to put the three files into the same directory on your system. If you are unable to work with the tar file package, the files may be downloaded separately from the AirMISR tools web page, http://eosweb.larc.nasa.gov/PRODOCS/airmisr/table_airmisr.html Be sure the three files reside in the same directory on your system. 6.1 Using a licensed version of the IDL software package The file read_airmisr.pro contains several procedures, so the entire file must be compiled before it can be run. To do this, the user must first start up IDL by typing "idl". At the IDL prompt, type ".compile read_airmisr", then type the program name, "read_airmisr" to start the program. Alternatively, the IDL development environment can be used. To start IDL this way, type "idlde" at the Unix prompt, select IDL from the Start menu on a PC, or click on the IDL desktop icon, if available. Under File, choose "Open" and then select the file read_airmisr.pro. Then click the compile and run toolbar buttons or, under Run, choose "Compile read_airmisr.pro" and then under Run, choose "Run read_airmisr". 6.2 Using the IDL Virtual Machine The IDL Virtual Machine is a free runtime version of IDL available from ITT Visual Information Solutions at http://www.ittvis.com/Downloads/ProductDownloads.aspx The IDL VM software may be downloaded from this site or ordered from ITT VIS on CD at no cost. The site provides installation instructions. To run an IDL VM application, 1) In Unix At the Unix command prompt, type idl -vm. Click anywhere on the IDL VM splash screen to continue. A dialog box appears for selecting the IDL save file. Navigate to the directory where you placed the read_airmisr.sav file and select that file. Click the OK button and the read_airmisr program will start. 2) In Windows, From Windows Explorer, drag the read_airmisr.sav file onto the IDL Virtual Machine Desktop icon created when the IDL VM was installed. Click on the splash screen, and the read_airmisr program will start. or Click on the IDL Virtual Machine desktop icon or run the IDL Virtual Machine from the Start menu and click on the splash screen to continue. Use the dialog box that appears to navigate to the directory where you placed the read_airmisr.sav file, select that file, and click OK to start the read_airmisr program. Note that the read_airmisr.pro source code file may be opened with any text editor to examine the processing algorithm. 6.3 Program Execution A dialog box displays the filenames for input file selection. The dialog box is created with a call to the IDL DIALOG_PICKFILE procedure that initially defaults to the current directory. The dialog allows navigation to the data file directory, if different. If running from the source code, the "Path" keyword in the call to DIALOG_PICKFILE may be modified to specify an alternate default directory. A second dialog box displays a list of available parameters. One or more parameters may be selected from the list to be written to the output file. The Help button provides platform-specific selection instructions. The hourglass cursor is displayed while program execution continues. When the program finishes, a pop-up message box appears to indicate completion. 7.0 Sample Output The read_airmisr.pro program can be used to read any of the AirMISR Georectified radiance product files, i.e., "GP" files. The following is a sample session showing compilation, execution of the program and portions of the output file. Compilation and Execution ------------------------- IDL> .compile read_airmisr IDL> .compile read_airmisr % Compiled module: READ_AIRMISR. % Compiled module: READ_GLOBAL_ATTR. % Compiled module: READ_GRID_ATTR. % Compiled module: GET_METADATA. % Compiled module: GET_GRID_FIELDS. % Compiled module: READ_GLOBAL_ATTR. % Compiled module: READ_GRID_ATTR. % Compiled module: MAKE_LIST. % Compiled module: WRITE_OUTPUT. % Compiled module: GET_FILE_INFO. % Compiled module: SELECTTOOL. % Compiled module: SELECTTOOL_EVENT. IDL> read_airmisr Output File (in part) --------------------- File: F:\Data\AirMISR\Howland\AIRMISR_GP_030828_155703_DF_F04_01.hdf Image Start Time = 2003-08-28T15:55:57.115000Z Image End Time = 2003-08-28T15:58:09.225400Z GridName="AirMisr" XDim=1808 YDim=1713 UpperLeftPointMtrs=(501466.000000,5030771.000000) LowerRightMtrs=(551186.000000,4983663.500000) Projection=GCTP_UTM ZoneCode=19 SphereCode=12 VALUES for Metadata ================================================================================ Name = UL Corner (deg): Latitude Longitude Data = 45.430460 -68.981259 -------------------------------------------------------------------------------- Name = LR Corner (deg): Latitude Longitude Data = 45.004572 -68.350506 -------------------------------------------------------------------------------- Name = Rad_scale_factor (1=Blue;2=Green;3=Red;4=Nir) Data = 0.047203224 0.046470445 0.038470935 0.024670249 -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- VALUES for Grid Fields ================================================================================ Name = Ellipsoid Red Scale Value = 0.038470935 Dimensions: XDim = 1808 YDim = 1713 Fill Value = 65535 Data = 65535.000 65535.000 65535.000 65535.000 65535.000 65535.000 65535.000 65535.000 65535.000 65535.000 65535.000 65535.000 ... skipping lines 26.044823 25.813997 25.737056 26.006352 26.121765 26.237178 26.198707 26.314120 26.737300 26.852713 26.968125 27.045067 ... skipping to the end of the file 65535.000 65535.000 65535.000 65535.000 65535.000 65535.000 65535.000 65535.000 65535.000 65535.000 65535.000 65535.000 -------------------------------------------------------------------------------- 8.0 Additional Information 8.1 References Bruegge, Carol J., Wedad A. Abdou, Nadine L. Chrien, Barbara J. Gaitley (1998). AirMISR spectral and radiometric performance studies. In Earth Observing System III, Proc. SPIE 3439, San Diego, CA, 19-21 July. Bruegge, C. J., N. L. Chrien, R. A. Kahn, J. V. Martonchik, David Diner (1998). MISR radiometric uncertainty analyses and their utilization within geophysical retrievals. Conference issue: New Developments and Applications in Optical Radiometry (NEWRAD '97), Metrologia., 35, 571-579. Bruegge, C. J., V. G. Duval, N. L. Chrien, R. P. Korechoff, B. J. Gaitley, and E. B. Hochberg (1998). MISR prelaunch instrument calibration and characterization results. IEEE Trans. Geosci. Rem. Sens., Vol. 36, pp. 1186-1198. Chrien, Nadine L., Carol J. Bruegge, Barbara J. Gaitley (2000). AirMISR laboratory calibration and in-flight performance results. Submitted to Remote Sens. Environment, December 1998. Diner, David J., et al. (1998). The Airborne Multi-Angle Imaging SpectroRadiometer (AirMISR): Instrument Description and First Results. IEEE Trans. Geosci. Rem. Sens., Vol. 36, No. 4. Last Updated: April 13, 2004 August 3, 2010 - changed link for ILD VM