Disclaimer

1. What LOS Analyzer computes

• Control-tower line of sight in 3D: sightlines from the controller's eye to runway points, traced over terrain with earth-curvature and standard atmospheric-refraction (k = 7/6) corrections, and tested against your proposed structure.
• 14 CFR Part 77 imaginary surfaces: computed from FAA runway data (the FAA's 28-day NASR release) for the linked airport, using each runway end's approach classification, and tested against the top of your structure.
• A PDF screening report of the inputs, results, map and assumptions.
• A Form 7460-1 pre-fill aid: a draft of the structure and location fields of FAA Form 7460-1, prepared from the same inputs, to help you prepare your own filing.

The methodology explains the method in full.

2. Data sources and known limits

• Terrain: ground elevations come from a public digital elevation model (USGS data served by OpenTopoData), sampled along each sightline. Vertical accuracy varies by region, typically ±5–15 ft. If the elevation service is unavailable, the analysis falls back to flat ground and the report says so.
• Things that are not modelled: trees and vegetation, existing buildings, poles, cranes and other local obstructions; non-standard refraction; and any structure shape other than a flat-topped prism of the stated height above local ground.
• Tower position and controller eye height: where LOS Analyzer pre-fills a tower, the position and eye height are derived estimates, not surveyed values. Eye heights for the seeded airports are derived from published tower information using the FAA Order 6480.4B convention and are rated medium confidence. You can and should replace them with verified values from the airport or the FAA. The analysis is only as accurate as these inputs.
• Part 77 surfaces depend on the runway data, classifications and threshold elevations used. Approach surfaces are modelled from each runway's threshold end. Some airports have no FAA runway data linked, in which case Part 77 is not evaluated and the app says so.
• Coordinates: the app and map use WGS84 coordinates from Google. The FAA works in NAD83 and may require coordinates and site elevation to a stated survey accuracy (for example, a 1A or 2C accuracy code). DEM elevations are estimates, not surveys.
• Data currency: FAA runway data are updated on the FAA's 28-day cycle; a change after the snapshot the app uses will not be reflected until the next update.

3. Using the Form 7460-1 pre-fill aid

You may use the pre-fill aid to prepare your own FAA Form 7460-1 filing. It never fills in proponent details it does not know. You, as the proponent, are solely responsible for:

• verifying every value before you file, including NAD83 coordinates and site elevation to the accuracy the FAA requires;
• deciding whether notice is required under 14 CFR 77.9, and filing through the FAA's OE/AAA portal on time;
• engaging a licensed professional engineer or surveyor where your project, the FAA or your jurisdiction requires one.

LOS Analyzer does not file anything on your behalf.

4. What you should not rely on it for

Do not present a LOS Analyzer report as, or rely on it in place of:

• an FAA Determination of No Hazard or Hazard, or any FAA aeronautical study;
• a surveyed site elevation or coordinates;
• a stamped or sealed engineering document, or the work of a licensed professional;
• a final building-permit, zoning, life-safety or airport-sponsor decision.

Using it to decide whether to file, to prepare a filing, to compare design options, or to brief your team, engineer or client is exactly what it is for.

5. No warranty; limitation of liability

The Service and its outputs are provided "as is", without warranty. Idea Engine's liability is limited as set out in sections 12 and 13 of the Terms of Service.