This was just posted by Duncan.
What Depth Was The TSBD Landing On November 22nd 1963?
This is a Gif I made of Dan Rather opening the TSBD glass door exit /entrance, and then walking on to the steps.
Unfortunately, the landing is not in view.
He does however appears to take two similar length strides/footsteps from the door exit/entrance before going down on to the top step.
As the average human stride/footstep, according to most information sources I have researched is approximately 31 inches, that would
make the depth of the landing from the glass door to the top step be approximately 5ft and a bit.
I did a test myself, and I can verify that this estimate is a reasonable calculation.