Help for AnaPol  "ANAlysis of POLder Products"
    F.M. BrŽon, CEA/DSM/LSCE, May 30th, 2002

  Version May 2005: Works for both POLDER and Parasol native products
    
      Comments and questions to fmbreon@cea.fr
      
GENERAL
This IDL based routine lets you visualize any POLDER product (Level 1, 2 and 3).
It is expected that the routine will work on any platform with an IDL Licence, 
although the development and extensive tests were done on a Macintosh.
Thanks to an optimized used of the memory, the memory requirements are less than
60 Mbytes.

The functionalities of the program are
- Selection of the region of interest from coordinates or using the mouse over a
  browse image
- Visualization of non-directional and "directional" parameters
- Multi-parameter false color composites
- Automatic or user-based min-max range.
- Animation of successive POLDER sequences (for directional parameters)
- Overlap of viewing geometry angles (for directional parameters)
- Extraction of individual pixel values
- Plots of parameter histograms
- Plots of parameter directional signatures, with several options for the angle
  of interest.
- Image saving in Jpeg format
- Data saving in HDF-EOS format

ORBIT SELECTION
The first step is to select a POLDER file (POLDER Product button).

AREA SELECTION
Next step is to select a region of interest.  A default region is proposed (this
region is centered on France for the first call).  You may use the "zoom" button
for a more accurate selection of the area.
For level-1 products, the "browse" button permits a quick view of the area cloud
cover.

DATA READ
Once the area is selected, proceed to data extraction (READ DATA button).  Data 
extraction and internal process may take up to one minute depending on your 
computer speed and the size of the selected area.  If a large area is selected, 
data is sampled with an appropriate step.

DATA VISUALIZATION
You may then visualize the various parameters available for the product.  Some 
parameters are "directional", i.e. they vary as a function of POLDER viewing 
geometry.  For such parameters, one may select the angle of interest.  These 
geometry angles are overlaid on the parameter display :
VZA : View zenith Angle by step of 10 degrees (Red)
SCAT: Scattering Angle by step of 10 degrees (Blue)
GLIT: Off-Glint Angle by step of 10 degrees (Blue)
AZI : Principal plane (Green)
One may also select whether a map shall be overlaid on the visualization window.

Note that the sampling is indicated on the window title.  When a region is 
selected, it is possible to zoom, in which case the POLDER product is read again
with a lower sampling.

COLOR SCALE RANGE
The color scale range may be defined either automatically or by the user 
(AUTO/USER toggle button).  The automatic range is set at 5-95% of the 
cumulative histogram.  In the user mode, it is necessary to validate the 
selected value (Carriage Return).

DEEPER ANALYSIS
With a single click on a pixel of the display area, three windows appear.
"Data Values" shows the actual values of the viewing angles and the reflectance 
values for the pixel and active sequence.
"Angular Positions" shows the viewing geometry for the various sequences 
observing this particular pixel [directional products only].  View Zenith Angles 
are in red, by step of 20 degrees.  Scattering angles or Glitter angles are 
shown in blue by step of 10 degrees if the corresponding button is pressed. The 
active sequence is indicated by a red mark.

"Reflectance Signatures" shows the reflectance as a function of the selected 
angle (VZA, SCAT, or GLIT), if at least one is selected.  The vertical line 
indicates the active sequence.
Note that two POLDER sequences may be acquired with the same angle.  To avoid 
confusion, negative angles are used for sequences on the left side of the 
"Angular Positions" plot.

With an area selection (i.e. the mouse is moved during the click), two windows 
appear.
"Angular Positions" is similar as above.  The angular position of all selected 
pixels is shown (note that the viewing geometry changes slightly from pixel to 
pixel).
The other window is context dependent.  If no angle (VZA, SCAT, AZI, or GLIT) 
is selected, an histogram of the four bands is shown.  If one angle is selected, 
the reflectance measurements are shown as a function of the corresponding angle.

SAVING IMAGES
The file menu lets you save any of the analysis windows.

SAVING DATA
The file menu lets you save the data in HDF-EOS format.  Note that the grid
that is used is "sinusoidal".  If the area of analysis is quite large and the
input data have been sampled, the output will also be sampled.

CUSTOMIZE ANAPOL
By default, most parameters of a given products are read and can be accessed
through the droplist.  For some POLDER products, this list is quite long, and a
user may prefer to access a limited list of parameter.  To do so, open the 
corresponding "define" file in the ANAPOL directory and comment the lines
corresponding to the parameters you are not interested in.