Robert West's plat (CE 585)

[Bob Prudhomme]

After time to think about your math, it seems to me that you are basing your figures on an assumption that Elm Street is a continuous 3 degrees slope from TSBD to point x. In fact Elm Street is level at the intersection of Elm and Houston and begins to slope down beginning at some point after you leave the intersection.


I think its far better to use the actual elevation changes measured by West, or by Robardeau in his map, than to imagine a perfect 3 degree slope from the base of the building to the street at point x.


Using those figures, I get an elevation change of (491.0 - 423.4) = 67.6 feet from nest to head (using the 53" measurement of JFK's head off the ground mentioned elsewhere in this forum). Measuring by Robardeau's plat map with pixel counting software (his scale is 4.14" per pixel) from nest to z313 (which incidentally matches a straight line between Nix and Zapruder, from the Nix photo at the headshot) you get a horizontal figure of 269.8 feet. The shot angle is (inv tan (67.6 / 269.8) ) or 14.1 degrees. The shot distance is SQRT((67.6)^2 + (269.8)^2) = 278.1 feet.

Hi Drew

I believe the actual average slope of the entirety of Elm St., to the Triple Underpass, is 3.13°, and you are correct, in that Elm St. is somewhat level in front of the entrance to the TSBD. However, this only makes the remainder of Elm St. that much steeper.

You are correct in surmising that the only thing that can be trusted are the elevation changes as determined by Robert West.

I have been a bit busy, as of late, and have only had a little time to work on my wooden "model" of Dealey Plaza. I had planned to simply have my Elm St. descend at a steady 3.13°, but this discussion has prompted me to go the extra distance, and use West's elevations to make it more accurate.

It is more difficult to precisely locate the shots, so I will simply have an area marked out from the Stemmons sign to the concrete steps, and use the entire section between the two sites to determine if JFK was at any time visible from the Sniper's Nest.