Antenna Base Moves Eastward for 9.5s Before Visible Initiation

Tracking Multiple Points To Detect Earliest Movement

Multiple points are tracked over the entire Sauret clip to detect vertical and lateral pre-release movement of WTC1.

The Sauret video

The first 20 seconds are the original Sauret video.


1) The camera shakes about 9.5 seconds before collapse.
2) The antenna and the NW corner of the building begin to slowly move during or immediately after the camera shake.

SOURCE VIDEO (Different from above)


1) Several static points in the foreground (3 on the metal stick, 2 on the windows behind stick). These "static points" in the foreground are represented by the blue curves.

2) "Static point" at the 92nd floor NW corner of WTC1 (yellow).

3) Several points near the roof (washer, roof corner, window at 110 NW corner). Roof measurements are represented by the green curves. The curve for the window of the 110th floor is a very bright green and appears almost white.

4) Antenna mast along the black/white transition. The movement of the antenna is represented by the red tones.


The trackers have a problem staying exactly in position during the shaking. Many trackers indeed lost the track and were not able to measure the assigned position during the entire length of the clip. Some trackers stayed "connected" but re-calculated the "best fit" several times during the shaking. Therefore we may have different relative positions of tracked points at the end of the shaking. That deviation of the curves doesn't mean that a real displacement of the measured points occurred. Instead we can use the new relative positions as "zero movement" if we are not able to track the movement during the shaking precisely.




Prior to the shaking of the camera all curves follow the blue "static foreground". There is no measurable movement of the tower. All apparent movements are the result of the shaking of the camera. After the shaking the yellow curve (floor 92) stays with the blue curves (static foreground). This means the 92nd floor didn't change it's position relative to foreground static points until the 92nd floor was pushed westward during the collapse.

Interestingly, all measured points above 92 - roof, washer (green) antenna (red) - started to lean east immediately after the shaking (about frame 1350).



Prior to the shaking of the camera all curves follow the blue "static foreground". After the shaking all curves vary somewhat but move with the blue curves for about the next 200 frames. At about frame 1465 the antenna mast clearly started to "sag" while roof (green) and 92nd floor (yellow) stayed with the static foreground (blue).

We will have to compare the result with the calculated relations for the south tilt before we can differentiate between tilt and drop. Nevertheless, prior to any sag/tilt the entire upper part of the buildings started to creep eastward.

The east leaning (wide side of the core) is hardly explainable as induced by the south wall inward bowing if we do not measure any increasing south tilt during this interval. The same object tracking tool is used to measure south tilt as well as eastward tilt. Any south tilt would significantly shorten the measured vertical distance between roofline and any tracked point on the antenna.

Perhaps we wouldn't notice a small trapezoidal perimeter deformation towards the southeast if the antenna remained straight up. In that case the perimeter columns would bow towards the southeast, yet the total circumference of thr roofline along the perimeter must remain the same and we do not see a corresponding movement of perimeter roofline columns extending from the SW corner to the NE corner. Therefore such a hypothetical SW perimeter fold-in as the antenna remains near plumb does not match the visual record and so can be excluded as a possibility.

Once again everything points to a core-led collapse, not to a collapse initiated by instability in the south perimeter..

Interesting to note that prior to the collapse the distance between roof and 92nd floor decreases as seen in the HiRes plot of vertical displacement. After the collapse of the 98th floor the 92nd floor was sagging (compared to the "blue" static points in the foreground) until it was destroyed when the collapse reached that floor.

Frame 1641 of that long enhanced video is the frame 0 of the older set of measurements by achimspok.

Originally posted at

Earlier Measurements of the Antenna Shift and W Wall Pull-in


The base of the antenna moved east.

The much higher elevation a (bright blue) moved almost exactly the way the roof did (bright pink). There is just a very small tilting at that time (growing difference between blue and pink. The displacement of the roof to the east isn't tilting. It's more like shifting - may be the core rotated about a low elevation and the perimeter followed that movement into a trapeze deformation. Otherwise we would measure a pretty obvious sagging of the NE corner.
Pull-in of the upper NW corner over 500 frames (8 seconds), visualized - horizontally stretched:

Pull-in of upper NW corner compared to the eastward leaning of the antenna over 500 frames (8 seconds)