You come off the north side of North Marginal Road heading due north onto the peninsula at 41.525168, -81.668573 — the existing service road, and the last land on the parcel's south edge before the East 55th basin.
Eighteen pairs of anodized blades run west from the turn on a 65:1 plane, each pair shorter than the last, tracing the approach surface that governs them. They reach the ground exactly where the primary surface begins — and that is where the road drops into the cut.
The airspace is not a constraint the design works around. It is the form.
The previous version of h_limit() took the minimum of a transitional surface and the approach surface — and because the transitional function returned zero for anything within 500 ft of the centerline at every station, it ran the primary surface east forever and reported zero allowable height for the full length of the parcel.
The primary surface ends 200 ft past the runway end, at U=5,173. Beyond it the approach surface governs inside its flaring trapezoid, and the transitional rises 7:1 off the approach edge — which is itself already climbing.
The sentence “driving the gate east buys nothing” in BEDC-007 §01 is withdrawn. Driving the gate east buys 8.5 ft at U=5,600 and 46.5 ft at U=7,500.
horizontal 1:12,000, vertical 10x
The primary surface ends at U=5,173. The old model ran it east forever.
Entry at U=5,950 on the parcel’s south boundary, at the service road already running onto the peninsula between the runway end and the marina basin. You come north off North Marginal, pass the arrival pair, clear the barrier and turn west.
The turn matters. The gradient row straddles the spine road, which runs east-west, because the approach plane descends with distance west. Approaching from the south you would pass that row sideways — which AR-10 caught. So a second pair, 10 ft, straddles the drive itself 200 ft back from the turn, giving the northward approach its own threshold.
From the turn it is 1,990 ft west to the head of the cut and 3,750 ft to hall 1.
1 in = 70 ft
You come off North Marginal heading NORTH and turn west onto the spine road.
Blade height is (U − 5,173) / 65 — a plane parallel to the 50:1 approach surface and 23% below it. One rule sets every blade and states the margin as a single number. The tallest is 12 ft at the turn; the shortest is 4 ft, below which a blade stops reading and the row simply ends.
Why 65:1 and not the 58:1 of Rev. A/B: the margin is proportional to the run, and over 517 ft instead of 1,895 a 58:1 plane leaves only 2.1 ft at the tallest blade. That is too thin against a runway centerline we have not surveyed. 65:1 gives 3.5 ft.
Eighteen pairs against thirty-six fin-wall bays — one pair for every two bays.
horizontal 1:2,400, vertical 4x
Thirty-six pairs, one per fin-wall bay, tracing the plane that governs them.
Only the threshold pair carries a fin field. The other seventeen, and the arrival pair on the drive, are plain anodized aluminum. Repeating the campus-load instrument on every blade would turn a sentence into wallpaper — and the instrument has 720 ft of wall further west where it can actually say something.
1 in = 8 ft
The only pair that carries the instrument. After it the row falls silent.
| Movement | Length | What the airspace allows | What it is |
|---|---|---|---|
| I — The Gradient | 517 ft | 12.0 → 4.0 ft | Height is available and falling. The blades draw the plane. |
| II — The Traverse | 273 ft | 4.0 → 0 ft | The last of the height runs out alongside the energy block. |
| III — The Cut | 1,200 ft | zero, the whole way | Nothing may rise, so the road goes down instead. |
This is what the correction actually bought. THE CUT was designed as the entire entrance when I believed the whole route was zero-height. It is better as the final movement of three — the place the sequence arrives at rather than the whole of it.
horizontal 1:14,000, vertical 12x
Three movements over 5,100 ft. The airspace writes the shape of all three.
From the turn to hall 1 is 3,750 ft on a single bearing. The only change of direction on the whole arrival is the turn west off the entry drive.
1 in = 420 ft
Gate to compute row. One axis, three movements, no turns.
Rev. A and Rev. B put the gate at U=7,300 on the strength of a corrected airspace model, without checking whether anything could drive there. Read against the source aerial, that point is 1,255 ft out into the East 55th basin.
The parcel's south edge is land from U=5,115 to U=6,045 and a shoreline east of that. The split was not eyeballed: pixel color sampled 20 ft south of the traced boundary goes blue-dominant and dark from x=1,010 east and stays that way to the east tip. The scale was checked first — the 24R pavement end reads U=4,960 against a known 4,973, 0.3% error.
as supplied, 6.20 ft per pixel
The evidence the siting is read from. Rev. A/B put the gate in the marina basin.
Every other view in this set looks west down the axis or east along the greenway. These two look due north, which is the direction the site is actually approached and seen from.
The honest result: from North Marginal, 930 ft back across the airfield, the campus barely registers. A 120-ft block at 1,300 ft occupies a fifth of the frame at a normal lens, and what fills the view is the energy block, not the compute halls — those sit far to the left. Whether that is a good outcome depends on the argument being made. For a lakefront the city is protective of, low visual impact is a defense. For a project that wants presence, it is a problem.
50 mm · heading 360.00° true · eye 5 ft 6 in, level
The civic view. What a driver on North Marginal actually sees: the energy block, not the halls.
28 mm · heading 000.00° true · eye 5 ft 6 in, level
What the arrival actually faces. The gradient row straddles the spine road and is passed heading WEST, after the turn - so a second pair straddles the drive itself to give the northward approach a threshold.
| Sheet | What it said | Status |
|---|---|---|
| BEDC-010 Rev A/B | Gate at U=7,300, envelope 42.5 ft | Wrong — sited in open water. Corrected to U=5,950 and 15.5 ft. The airspace model was right; nobody checked the ground under it. |
| BEDC-010 Rev A/B | 36 pairs over 1,895 ft, tallest 36.7 ft, 58:1 plane | Corrected to 18 pairs over 517 ft, tallest 12.0 ft, 65:1 plane. The plane ratio changed because 58:1 over the shorter run left only 2.1 ft of margin. |
| BEDC-010 Rev A/B | A single threshold pair on the spine road | The arrival comes from the SOUTH, so that row is passed sideways. A second pair now straddles the entry drive. Caught by AR-10. |
| BEDC-001 | Zero allowable height: 70.1 ac (39.5%) | Corrected to 40.5 ac (22.9%). Needs reissue. |
| BEDC-001 | Only 1.0 ac permits 120 ft | Corrected to 0.4 ac. The conclusion is unchanged and if anything stronger. |
| BEDC-001 | Case A: on-site generation physically impossible | Unchanged and still correct. A 180-ft stack at U=6,060 faces a ~42 ft limit. It busts the approach surface either way. |
| BEDC-002 | Case A envelope maps east of U=5,173 | Understate available height. Flagged; not yet reissued, because Case A puts nothing out there. |
| BEDC-007 §01 | “Zero from U=4,600 to U=7,973” | Corrected to U=4,600 to U=5,173. Reissued with this sheet. |
| BEDC-007 §01 | “Driving the gate east buys nothing” | Withdrawn. It buys 8.5 ft at U=5,600 and 46.5 ft at U=7,500. |
| BEDC-007 | THE CUT as the whole entrance | Re-cast as movement III of three. The design of the cut itself does not change. |
| Unaffected | Everything west of U=5,173 | The halls, the cut, the greenway at 43.1 ft, the 7:1 transitional, every Case B scheme. The model was always right there, and the regression test confirms it is still identical. |
The error was caught by your correction that the entrance is on the north side of North Marginal east of the working airport. Checking whether that location was buildable is what exposed it.
No blade in the row penetrates the approach surface — the tallest clears by 5.8 ft. But penetration is not what triggers notice.
14 CFR 77.9(b) requires a Form 7460-1 filing for anything exceeding a 100:1 slope measured from the nearest point of the nearest runway, out to 20,000 ft, for runways longer than 3,200 ft. Burke 6L/24R is 6,198 ft, so the 100:1 rule applies — and it is far more restrictive out here than the approach surface is.
This is notice, not prohibition. Since nothing penetrates a Part 77 surface, a “no hazard” determination is the expected outcome — but the filing is mandatory, it covers 12 of the 18 gradient pairs plus both arrival blades, and it should be made as one submission for the whole installation rather than blade by blade.
| Item | Note |
|---|---|
| SURVEY FIRST | The envelope is measured from the 6L/24R centerline, and the centerline position is the one dimension on this site taken from published geometry rather than from the ground. Survey it before any foundation is poured. |
| NO SPAN | A portal beam at 36 ft is the obvious gesture and the wrong one: a horizontal member near a runway approach is a perch, and AC 150/5200-33B does not want perches within 10,000 ft. Two free-standing piers do the same work. |
| LIGHTING | Amber only, shielded, downward. No obstruction lighting is required below 200 ft and none should be added voluntarily — a blinking red beacon on the lakefront is exactly what this design is trying not to be. |
| FRANGIBILITY | At 1,000 ft from the runway end the row is outside the object free area, so standard structural design applies. Confirm against the current ALP. |
| GLARE | Anodized and diffuse. The blades face the road, not the approach. |
| BEDC-007 | Arrival gateway — the cut, the fin wall, the greenway line. Reissued with the corrected envelope. |
| BEDC-008 | Eight eye-level views, AR-1 to AR-8 |
| BEDC-009 | Eight render prompts keyed to those views |
| BEDC-010 | This sheet — the east gateway and the model correction |
Open: BEDC-001 still needs its acreage corrected, and the 7460-1 filing should be scoped as one submission. The gradient now has views — AR-9 and AR-10 in §08.