The four IDL procedures in this directory constitute Version 2.1 of a data browser
and editor for SLICER data files.  The V. 2.0 update includes corrections for proper
operation on Intel-based (Windows and VMS) systems, and several browsing and
editing enhancements.  Refer to the on-line instructions and prompts for these
enhancements.  This README file also includes updated usage notes.
V. 2.1 includes an additional option for selecting the height range on the waveform
plot, allowing a variable range defined by the distance to the ground return on a
shot by shot basis.

A sample data file (sample.dat) is also included in the directory for use with
the browser.

The browser plots four IDL windows containing:

1) a map view of profile ground tracks
2) SLICER elevation profiles of canopy top, canopy inflection and ground returns
3) a perspective view of ground to canopy top vectors for each laser shot
4) individual laser shot waveforms (return echos) along the profile.

A fifth window provides user instructions and prompts.

Datwaves.pro is called from IDL 5.0.3, or later version, by using 
IDL> @readdata, and following on-screen instructions for interactive 
data browsing and editing (earlier distributions of this browser incorrectly
stated that it was compatible with IDL 4.0.1). This IDL data browser is known to
operate correctly in UNIX and Windows environments.  It should also operate under
Mac and VMS but has not been tested in these environments.

User responses to prompts in the instructions windows are entered in the IDL
command window from which @readdata was run.  This command window must be
positioned so as to not be covered by the 5 windows created by the data browser
(top of the screen in UNIX, bottom of the screen in Windows).

PC users must set their display bit depth to 8 for proper display of IDL colors.

The databrowser saves plot window definitions in 4 files (w0.sys, w1.sys, w2.sys,
w3.sys) that are saved in the directory from which @readdata is run.  Thus the
user must have write privileges in the directory from which they run the browser.
Because IDL Demo mode does not permit saving these .sys files, the browser does
not function properly in Demo mode.  A full IDL license is required.

Readdata.pro contains the structure definition of the binary
.dat data files.  These files contain only bytes or scaled long integers, 
using the Motorolla (UNIX and Mac) byte order convention. 
Readdata creates a structure named "dat" in idl that contains the data
parameters for each laser shot. Readdata then calls convertd which
subsets the data to a selected range of laser shots, swaps byte order
to the Intel (PC or VMS) convention, if necessary, and then converts the
.dat parameters to physical units using appropriate scaling factors, saving
them in a structure named "b".  Readdata then runs inflecpt.pro which derives
the parameter infl, the distance from the canopy top to the maximum return
amplitude within the canopy.  For simple, single-story canopies this is
equivalent to the inflection height of canopy leaf area index (LAI).  The
infl parameter is probably not appropriate where canopies are multi-storied.
Datwaves.pro is then called and interactively displays the data and
allows editing of the ground return position.


David J. Harding
NASA's Goddard Space Flight Center
Mail Code 921
Greenbelt, MD 20771
harding@denali.gsfc.nasa.gov 

8/17/98