"ellacc.doc - 1.4 - 2003/01/10"
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            DOCUMENTATION for NGS program ellacc
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PROGRAM FUNCTION:

Reads an output file from program ADJUST and 
computes ellipsoidal height order-class accuracy distributions,
both as an aggregate, and grouped by baseline lengths.


PROGRAM OPERATION:

Entering "ellacc -h", or any other single parameter,
results in a help screen displaying the program usage.

Entering only "ellacc" results in prompts for data input.

To run the program in command line parameter mode,
the command line must have:
  0) ellacc, the program name
  1) the  input file, which is an existing output file from the adjust program
  2) the output filename, formed at the user's discretion
Optionally, the command line may have:
  3) accession (job) number

Example:
  ellacc  adjust7.out ellacc7.out GPS257
where
  adjust7.out  is an existing file generated by the adjust program
  ellacc7.out  is a label from the user's discretion,
               to record output of this program
  GPS257       is the optional accession number

If the input file cannot be found, then
the program ends with an error message,
displaying the input filename, to help check for typo errors.

If the output file cannot be created (rare), then
the program ends with an error message,
and advises to check available memory.
The user may also check for an existing read-only file of the same name.

Job statistics are prepared, and written to both display and output file:
  - System run time
  - Input  filename
  - Output filename
  - Accession number, if it was entered

This program tests the second, "PROGRAM ADJUST" record, for format type.
The Adjust version from the third record is only reported, not tested.


The program reads through the adjustment results file,
and sequentially extracts a baseline distance and 
a figure associated with the standard deviation of the vertical angle
associated with the baseline.

This vertical angle is measured between the plane which is normal 
to the ellipsoid normal through the standpoint,
and the point-to-point baseline to the forepoint.
This angle is measured positive upward from the plane.
See Technical Memorandum 47 (also TM-17) for geodetic geodesy details.

The Adjust output file records a value 
that is the sine of the standard deviation of this vertical angle,
multiplied by the baseline distance,
to yield the standard deviation of the ellipsoid height of the forepoint.

This value is read, then units converted from meters to kilometers,
then scaled to 2 sigma (95% confidence interval),
and then divided by the baseline distance to yield an accuracy ratio:

   95% std deviation of forepoint ellipsoid height (kilometers, 2 sigma)
   ---------------------------------------------------------------------
                    baseline distance (kilometers)

and the accuracy ratios are grouped by the limits:
           ratio  < 0.5
   0.5 <=  ratio  < 0.7
   0.7 <=  ratio  < 1.0
   1.0 <=  ratio  < 1.3
   1.3 <=  ratio  < 2.0
   2.0 <=  ratio  < 3.0
   3.0 <=  ratio  < 6.0
   6.0 <=  ratio  < 15.0
  15.0 <=  ratio  < 30.0
  30.0 <=  ratio  < 60.0
  60.0 <=  ratio

The program then loops back to get the next set of data.


After all records from the adjust output file have been examined,
then the number of each accuracy ratios are then reported:
  - as an aggregate
  - by baseline length grouping:
                baseline  <  25 km
      25 km <=  baseline  < 100 km
     100 km <=  baseline  < 250 km
     250 km <=  baseline

These reportings are printed both to the output file and the display.

Finally, a message is printed to display to show program completion,
"Normal end of program ellacc"

ellacc.doc - end
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