Measurements on the drum scan of the Moorman photo indicate that the "gap" measures 6.7 inches in height at the camera location.
This figure can be independently evaluated by measurements performed on the site.
These measurements were carried out by Gary Mack, Josiah Thompson and Ron Hepler on the afternoon of March 16, 2002 in Dealey Plaza. Dr. Don Thomas offered advice but did not participate in the measurement process. A tripod and Thompsonís Canon EOS Elan 35 mm. camera were used with a zoom lens (35 - 135 mm.) Exposures were made at various settings oscillating around f8 at 1/250 second.
First, the camera was set up on the tripod over the south edge of the Elm Street curb near the yellow spot with the White "cross" LOS lined up. The height of the center of the lens above the curb was measured. It was 49 inches. A position along the same line of sight but two feet south of the Elm Street curb was selected. Using a level and a measuring stick, it was determined that this point was 4.75 inches above the level of the curb. Hence, a curb height of 49 inches accords well with White's original measurement of the "cross" LOS as lying 44.5 inches above the turf two feet from the curb.
We then moved our camera a few inches to the left along the curb to replicate the LOS apparent in the Moorman photo. We took photos with the center of the lens at the following heights above the Elm Street curb
53.75" 54.75" 55.75" 56.75" 57.75"
Hepler, Mack, Thomas and Thompson all looked through the viewfinder and finally settled on 55.75" as the best replication of the Mooman LOS. This position would yield a "gap" height of 6.75 inches at the camera location, thus empirically confirming the 6.7 inch figure resulting from measurements on the drum scan of the Moorman photo.
In addition, photographs were taken with Ron Hepler standing on the pedestal with a measuring rod with black bands one inch apart. Eight (8) quarters were placed in a column atop the left front corner of the pedestal. These quarters simulated the 0.55 inch "gap" at the pedestal calculated by Dr. Costella. The quarters are virtually indiscernible in photographs taken to simulate Moorman's photo.