Lake Pontchartrain towers and causeway sight lines
The transmission line and the causeway are different observations. Compare dated positions and height datums before fitting a curve to a cropped image.
30° 17′ 38.00″ N, 90° 18′ 38.00″ W; transmission tower; 210 ft above ground, 211 ft above mean sea level; verified O status in the 27 September 2026 data cycle.
FAA obstacle 22-000219
30° 17′ 49.00″ N, 90° 18′ 33.00″ W; another transmission tower; 210 ft above ground, 211 ft above mean sea level. Two catalogue records do not describe every tower in the crossing.
A separate dated image
Caraccioli’s own image record describes a 5 January 2019 causeway photograph with Sony a7R II and an 8-inch Schmidt–Cassegrain telescope, combined from 19 frames.
Height datum
AGL height is above the recorded ground reference, not automatically above the lake’s instantaneous water surface. Enter water level and the observation’s measured eye height in a common datum.
Compare eye height, distance and light path
RUN THE NUMBERS
Change the sight-line scenario
These starting values define a comparison scenario. Replace the eye height, surface distance, target height and atmospheric assumption with your own paired observation.
Unit changes preserve the same physical inputs. The working tape stays in SI units.
Hidden target height
Minimum radial height at the target needed to meet the limiting ray; zero before the observer’s horizon.
Visible target height46.46 m
The entered target above the limiting ray; zero means the whole target is below that smooth-surface sightline.
Enter one camera station to compare the FAA coordinates above. The starting station is a calculation scenario, not the station of a historical photograph. Elevation here is above mean sea level; the recorded tower tops are 64.3128 m AMSL.
FAA tower
Surface range
Compass bearing
Spherical top angle
Level-plane top angle
22-001038
10.489 km
354.455°
0.2932°
0.3404°
22-000219
10.816 km
355.333°
0.2815°
0.3301°
Both columns use the same recorded top elevations and surface ranges. The spherical column projects a straight ray relative to the camera’s local horizontal; the level-plane column places those ranges on a level plane. Neither fits atmospheric bending, lens distortion or intervening obstructions. Compare angular separation and elevation with identified tops in an uncropped frame. These two records are a subset of the crossing, and their 2026 elevations do not reconstruct every structure in a 2017 image.
Identify which line is being measured
The west-lake power line contains elevated transmission structures, while the highway causeway consists of many short spans and navigation passages. A photograph of one cannot supply the heights or alignment of the other. The two FAA tower coordinates shown here are catalogued obstacles; their height reference is separate from a photographed horizon.
Caraccioli’s causeway image has a dated original record. The image description and a surveyor’s camera record number the hotel floor differently, so use the actual surveyed camera height instead of converting a floor label into metres. This avoids silently treating a building-floor convention as an observation.
Perspective needs range as well as elevation
For a sequence of equal-height structures, every structure has its own distance and apparent vertical angle. Project those angles from one camera position. Drawing a line through the image’s tower tops without identifying ranges can confuse perspective with height differences.
The starting 20 km separation and 2 m eye height are scenarios. The 64.008 m target converts the catalogue’s 210 ft AGL; replace it with height above the measured water surface for an observation. A September 2026 catalogue entry is not proof that all dimensions of a 2017 photograph were identical.
Reconstruct a repeat observation
Record the camera station, water level and each matched tower or bridge feature at one date and time. Survey distances along the alignment rather than spacing markers evenly by their size in a photograph. Keep an uncropped frame so camera roll, lens projection and horizon placement can be checked.
Compare a straight-ray spherical prediction with an entered refraction scenario, then repeat at another eye height. The tower bases, tips and water horizon should be matched separately. Variable near-water temperature gradients need the layered-ray comparison rather than a universal refraction value.
