AIRMISR_HOWLAND_2003 Data Set Readme
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1.0 Introduction
 
This file contains information about AirMISR data taken during a flight over
the  Howland Forest, Maine, 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 28, 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_HOWLAND_2003

There were a total of two runs during this flight. Each 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, b) Level 1B2 Georectified radiance product from 
one of the 9 camera angles, or c) Level 2 Land Surface product combined from 7 
view 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_HOWLAND_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, 2 S. Wright St.
Hampton, VA 23681-2199
USA
E-Mail: larc@eos.nasa.gov 
Phone: (757)864-8656 
FAX: (757)864-8807
 
2.0 Data Set Information 
 
This flight over Howland Forest, Maine, 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 Earths 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
 
Three types of AirMISR data products are available through the Langley 
Atmospheric Science Data Center. These are 1) the Level 1 Radiometric 
product (L1B1), 2) the Level 1 Georectified radiance product (L1B2), and 3) 
the Level 2 Land Surface products (L2AS).
 
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.

The Level 2 Land Surface Product (AS) consists of a set of retrieved surface 
parameters, a camera mask indicating which view angles are used in the 
retrievals and corresponding data quality indices (DQI).  The surface 
parameters include the hemispherical-directional reflectance factor (HDRF), 
bi-hemispherical reflectance (BHR), the Raman-Pinty-Verstraete (RPV) model 
parameters, bidirectional reflectance factor (BRF) and the directional 
hemispherical reflectance (DHR).  It should be pointed out that out of the nine 
AirMISR camera views, a maximum of seven cameras are used for this version of the 
retrieval.  The most oblique D camera view angles are excluded from 
computations due to significant co-registration offsets.  The surface 
parameters include the hemispherical-directional reflectance factor (HDRF), 
bi-hemispherical reflectance (BHR), the Raman-Pinty-Verstraete (RPV) model 
parameters, bidirectional reflectance factor (BRF) and the directional 
hemispherical reflectance (DHR).
 
2.1 Data Quality

2.1.1 Radiometric Data Quality
 
The science flights made by AirMISR over the Howland Forest, Maine, target on 
08/28/2003 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.
 
2.1.3 Land Surface Data Quality

AEROSOL DEPENDENCY
The land surface product relies on the quality of the aerosol properties
used in the atmospheric correction procedure. This aerosol information 
(optical depth, aerosol type, mixture file, scale height, base altitude,
top altitude) is reported in the AirMISR Metadata and is derived from
multi-band sun photometer data taken during the AirMISR overflight of the 
target. 

RELIABILITY OF LAND SURFACE REFLECTANCE VALUES 
Because the two AirMISR datasets at the extreme view angles (~70 
degrees) can be very difficult to adequately co-register routinely to 
datasets at the less extreme AirMISR view angles, only the seven 
images with view angles between ~60 forward and aftward are used to 
create the land surface product.  For low surface albedo areas, the
atmospheric correction scheme should be considered most reliable when 
the aerosol optical depth is small (< 0.3). For higher albedo areas, 
good results are obtained for larger optical depths (< 0.4). Thus, it 
is recommended that users examine the aerosol optical depth field in the
Metadata as part of their assessment of the surface parameters. For
most AirMISR data, the aerosol amount is not the limiting factor 
affecting the quality of the retrievals. More important factors are 
multi-angle pixel co-registration accuracy and possible 3-dimensional
(adjacency) effects affecting high contrast areas.   

FILL VALUES IN LAND SURFACE REFLECTANCES
Land surface reflectances are computed separately for each AirMISR pixel 
and for each spectral band. For some pixels, the AirMISR radiances can
be of sufficiently low quality (e.g., noise contamination) to 
prevent a retrieval. In this case a fill value for the land product 
is archived.

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
 
The AIRMISR_HOWLAND_2003 data files are named in the following 
manner, where all elements within the <> symbols are variable. 
 
AIRMISR_RP_<yymmdd_hhmmss>_<CamAng>_F<format_version>_<file_version>.hdf

AIRMISR_GP_<yymmdd_hhmmss>_<CamAng>_F<format_version>_<file_version>.hdf

AIRMISR_AS_<YYmmdd_hhmmss>_F<format_version>_<file_version>.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

AIRMISR_AS: HDF-EOS file containing retrieved land surface 
parameters derived from L1B2 geolocated radiances
 
<yymmdd_hhmmss>: date and time in UTC computed from ER-2 navigation for 
image mid-point in the downtrack direction.

<CamAng>: 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

<format_version>: 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.

<file_version>: 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.

AIRMISR_AS_030828_160144_F04_01.hdf

AirMISR Level 2 AS  Land Surface product taken on August 28, 2003 with the 
image mid-point at 16:01:44 UTC. Data values are derived from seven viewing 
angles, the format version is 04 and the file version is 01.

 
3.3 Image Naming Convention
 
The AIRMISR_HOWLAND_2003 "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_<yymmdd_hhmmss>_<CamAng>_F<format_version>_<file_version>.
  <band>.<size>.png
 
<band>: blue, green, red and near-infrared spectral bands.
<size>:	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_<yymmdd_hhmmss>_<CamAng>_F<format_version>_<file_version>.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

4.3 L2AS Grid Field Parameters
--------------------------------------------------------------------------------
Parameter         Data Type  Fill Value   Units     Description
--------------------------------------------------------------------------------
LandHDRF          float32    -9.990E+02   unitless  hemispherical directional
                                                     reflectance factor
LandBHR           float32    -9.990E+02   unitless  bi-hemispherical reflectance
LandBRF           float32    -9.990E+02   unitless  bidirectional reflectance 
                                                     factor
                                                    Raman-Pinty-Verstraete
                                                     model parameters from a fit
                                                     to the surface BRF:
BRFModParam1      float32    -9.990E+02   unitless   r0         
BRFModParam2      float32    -9.990E+02   unitless   k          
BRFModParam3      float32    -9.990E+02   unitless   b
LandDHR           float32    -9.990E+02   unitless  directional hemispherical
                                                     reflectance
CameraMask        uint16        65535     unitless  bit mask indicating view
                                                     angles used in surface
                                                     retrieval
DQI               uint8           255     unitless  data quality index
 
Note:  There are four fields for each of these parameters, one for each wavelength.
Field names match parameter names with the wavelength color appended, e.g.,
LandHDRF Blue.   

4.4 L2AS Grid Attribute (Metadata) Parameters
--------------------------------------------------------------------------------
Field                              Data Type Units        Description
--------------------------------------------------------------------------------
Pressure                           float32   mbar         atmospheric pressure
                                                           at surface
Rayleigh optical depth             float32   unitless     measured from surface
                                                           to top of atmosphere
Aerosol optical depth (green band) float32   unitless     measured from surface
                                                           to top of atmosphere
Ozone optical depth                float32   unitless     measured from surface
                                                           to top of atmosphere
Aerosol type                       int32     unitless     aerosol model number
Mixture file                       char8     unitless     full path file name of
                                                           the input aerosol
                                                           mixture file
Scale height                       float32   km	          aerosol scale height	  
Base altitude                      float32   km           height of bottom of
                                                           aerosol layer
Top altitude                       float32   km           height of top of
                                                           aerosol layer

5.0 Description of Sample Read Software 
 
Currently, there is one sample read program which reads both the Level 1B2 
Georectified radiance product ("GP" files) and Level 2 Land Surface
parameters ("AS" files), read_airmisr_v3.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 but
will read only 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_HOWLAND_2003 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_v3.tar, which can be 
opened on both Unix and Windows systems.  The tar file contains the
read_airmisr_v3.pro source code file, the read_airmisr_v3.sav executable file, and a
bitmap logo file, read_airmisr.bmp.  

On Unix systems, use the command
    tar read_airmisr_v3.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_v3.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_v3", then type
the program name, "read_airmisr_v3" 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_v3.pro.   Then click the compile and run toolbar
buttons or, under Run, choose "Compile read_airmisr_v3.pro" and then under  Run,
choose "Run read_airmisr_v3".

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/idlvm/
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_v3.sav file and select
that file. Click the OK button and the read_airmisr_v3 program will start.

2) In Windows,
From Windows Explorer, drag the read_airmisr_v3.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_v3 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_v3.sav file,  select that file, and click OK to start the
read_airmisr_v3 program.

Note that the read_airmisr_v3.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_v3.pro program can be used to read any of the 
AIRMISR_HOWLAND_2003 Georectified radiance product files, i.e., "GP" 
files as well as the Level 2 Land Surface ("AS") product 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_v3
% 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_v3

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 March 10, 2004