3D Modeling

[James Hackerott]

Very impressive, thank you for this info. I think if I was 20 years younger I’d be all over this. But I do have a very talented and generous cousin making 3D trinkets, puzzles etc. as gifts. He does not do any computer design or editing, but probably would enjoy such a 3D printing challenge. I don’t know any of his equipment’s requirements or capabilities but would expect the exploded parts scheme would be used.  I asked him jokingly to print for me a 3D printer for our last family reunion. Sure enough, he did. It is all in parts, that need 20 or so very tiny screws to assemble it. Of course it is for display only and not functional. I suppose there are 3D printing services readily available, but keep in mind when you are satisfied with your model.

[James Hackerott]

Was applying some of James Hackerott's on-site measurements to the Underpass model.

And was looking at some pictures when I noticed something odd.

East Side

West Side

The two single pillars in the center of the bridge project outward from the bridge more than the walkway tunnel twinned pillars. Maybe half a foot? Am I wrong?

I’ve updated my 3D model for the TUP’s bridge and tunnel columns for comparison of their shadow length along the base of the underpass (green in the simulation). For reference I modeled the scene to overlap a photo from the west that I took last year 220927_125830 (with known sun azimuth and altitude).  I then replaced the north column of the south tunnel (right side of frame) and incrementally decreased its separation from the bridge until the the shadow overlapped the reference frame. This overlap came at a 11-12” decreased separation.  I also did the same modeling for an image taken from the south Elm storm drain. However, that image was taken from a camera generated 360 panorama that stitched many frames, without regard of quantitative analysis. Nevertheless, modeling gave a similar estimation to the first result of about 12” recession compared with the bridge columns.


An easier view:

[James Hackerott]

For the bridge and tunnel column profiles I used an image I took in 2019 looking north from the south tunnel (guesstimate midway between the two tunnel columns). The camera image has a field of view of 65.5 degrees. With help of Google Earth to estimate distances I calculated the dimensions shown in the image. I did this for each of two photos taken with slight shift for stereo and am showing the results from each photo. A crude approach, but actual measurements with a measuring rule were little more than SWAG anyway.

[Jerry Organ]

Thank you, James. This is good information I'll incorporate into my model.

A while ago, you posted about the heights of the bridge columns ( Link ).

    "With the laser I measured the heights above curb of the second
     column from the north (south side of sidewalk) on both the east
     and west sides. The height for the east column is 24’ 5” while the
     west column is 23’1”.  The difference of 16” over 124’ gives an
     average slope of -0.58 degrees in the westward direction."

One source said that not including the railing aspect of the Triple underpass, the [road into the] Underpass is 24 ft lower than the level of Houston street. I understand you measured the two columns from the top of the sidewalks but where to the top? That is, it would seem 24' 5" is not to the very top of the pillars but maybe to the bridge roadbed or the top of the railing?

[Jerry Organ]

Re: Previous post.



The eastside pillars being 24' 5" in height (from sidewalk surface to very top of pillar) means the top of the pillars are level or nearly-level with Houston Street. I think we see something like that in the photo on the right.

Therefore, the traffic roadbed that enters the bridge tunnels on the east are roughly 24' below Houston. The Commission used the rounded figure 24'. I was under the false impression that the flat surface (on which trains run) of the bridge was level with Houston. It is actually several feet below Houston.

Must be a slight downhill grade between the Depository and the rail-bridge. I believe I can make it work now. Thanks.

[Charles Collins]

This probably won’t be helpful but I saw it online and found it interesting:

[James Hackerott]

Thank you, James. This is good information I'll incorporate into my model.

A while ago, you posted about the heights of the bridge columns ( Link ).

    "With the laser I measured the heights above curb of the second
     column from the north (south side of sidewalk) on both the east
     and west sides. The height for the east column is 24’ 5” while the
     west column is 23’1”.  The difference of 16” over 124’ gives an
     average slope of -0.58 degrees in the westward direction."

One source said that not including the railing aspect of the Triple underpass, the [road into the] Underpass is 24 ft lower than the level of Houston street. I understand you measured the two columns from the top of the sidewalks but where to the top? That is, it would seem 24' 5" is not to the very top of the pillars but maybe to the bridge roadbed or the top of the railing?

My apology for the confusion. My goal was to measure bottom to top of the columns. This turned out to be more difficult than I anticipated. What I should’ve written is “I measured the heights above the pedestal tops…” for the tunnel columns. Columns W1, W2 and W3 are numbered from the north increasing southward. The same for the east columns E1, E2 and E3. I began the measuring project with bridge column E3, which does extend down to the curb. The same with W3. I then began measurements of the tunnel columns W1 and W2. But for the tunnel columns I was not able to get direct (single) measurement from the top to curb, so decided on using the pedestal top as a base. My thinking then was to know the pedestal heights and add the two measurements. But the tunnel pedestals don’t reach the curb as they sit on blocks above the curb. It appears I did not make measurements of those blocks. Therefore, I can only provide column top to pedestal top lengths for tunnel columns. Here are data for each column. Precision or accuracy is not impressive.
Uh, would all of the pillar pedestal tops be at the same elevation?

   Column Top to Pedestal Top
W1   21’4” (seems low, perhaps I measured the middle ‘step’ instead of the top)
W2   23’1”
E1   22’7”
E2   22’10”

   Column Top to Curb
W3   30’0”, 28’6” (Elm traffic interfered with measurements, so no attempt to keep trying)
E3   27’3”, 27’7”

[James Hackerott]

I may be the last to know this. I just looked at Dealey Plaza in Google Earth Pro-with 3D Buildings layer. Elevation data is not only given for buildings but trees, plaza structures and even automobiles parked in the lots! Elevations for some details of the TUP are available. All elevation data are given with 1 foot resolution.

Elevation, Ft
426      Center of Houston St. / Main intersection
400      Elm just at the underpass
398      Elm just after the underpass
419-420   Top of bridge at track level
423      Rail
426      Top of East Elm/Main pillar