This packet contains the following files:

DPDstudy.bas - The DPD tape echo study program written in QBASIC.
DPDstudy.exe - The DPD tape echo study program compiled with First BASIC.
Dplaza.gif - My computer-drawn map of Dealey Plaza.
DPDstudy.txt - This text file describing the DPD tape echo study program.

     The DPD echo study program simulates the analysis done for the HSCA by
Professors Weiss and Aschkenasy on the DPD tape which found a match of one
of the sets of impulses on the DPD channel 1 tape with a predicted pattern
of echoes from a hypothetical gunshot from the grassy knoll. The HSCA 
recommended that the same type of analysis be applied to the other shots
as a confirmation of the validity of the method. The DOJ refused to do so.

     This BASIC program was converted to QBASIC for the IBM from an old
Commodore BASIC program which I wrote many years ago. Not every feature
could be translated elegantly. And there are some flaws and uncertainties
which make it impossible to achieve a perfect match between the DPD tape
impulses and predicted echo patterns. There are several variables for which
we do not know the true values with absolute certainty. We can only use a 
reasonable estimate. I have provided default values which are assumed to be
very close to the true values for some of these variables, such as the
position of the rifle, the position of the cycle, the speed of the cycle,
and the speed of sound. There are some very minor variables which have been
left out entirely, as they have barely neglible impact on the matching
process, such as the recoil of the rifle, acceleration or deceleration of
the cycle, change of elevation while the cycle is moving, variations in the 
speed of sound due to wind or shading, or variations in the speed of sound
due to the type of materials which reflect or refract paths. Additionally,
only direct path echoes are calculated, not compound echo paths as Weiss
and Aschkenasy were able to do. If anyone has suggestions on how to add this
type of calculation, please E-MAIL me the code. Also, you may notice that
there are some differences between the QBASIC program and the compiled BASIC.
First BASIC was the only shareware QBASIC compiler I could find, so if you
can compile it with something better, please do so and E-MAIL it to me.

     Most of the screen output and printout shoud be self-explanatory, but
there is one field which is not explained. The field just before the word
"**BLAST**" is a sum-of-squares calculation which I use as a visual check 
to see if the matching process is getting better on subsequent runs. Since
the predicted blast will always be 0.0 due to the fact that this begins
the matching process, this field did not need to be displayed and could be
used to keep a running check on the sum-of-squares calculation. Any value
above 20 shows poor matching. Any value closer to 10 would indicate a much
better match. Anything near 5 would be an excellent match. When you choose
to do the extended calculations (F11) you can watch the sum of squares drop
until it remains constant, at which point that run has found the best
available match for those variables. If you get results with a sum of squares
less than 10, please E-MAIL me at amarsh@quik.com with the variables you used.