Civilian Airports / Obstructions
Obstructions
FAA Part 77 imaginary-surface evaluation for anything near the runway, checked against real survey coordinates.
The problem
An obstruction question multiplies by every surface at once
A new antenna, a construction crane, a stack of equipment near the runway: whether it's actually a problem depends on checking it against every imaginary surface Part 77 defines for that runway, not just how tall it looks standing next to it. Doing that by hand, surface by surface, runway by runway, every time something new goes up, is where a real evaluation quietly turns into a guess.
And a result that lands close to a surface boundary only means something if the geometry behind it can be trusted. A distance eyeballed off a satellite image, or a heading rounded to the nearest compass point, isn't the standard an actual evaluation is held to.
How it works
Placed on the map, checked against Part 77 at once
- 01
Tap the map, or use your device's location
Tap the object's spot on a satellite view of the airport, or pull up the page on a phone while standing next to the object and let it read the position, then note the height above the ground.
- 02
Checked against Part 77, not eyeballed
The object is evaluated against the surfaces 14 CFR §77.19 defines around the runway (approach, transitional, horizontal, and conical), computed from the airport's own FAA survey coordinates instead of a rough estimate off the satellite image.
- 03
Ruler and layers to see the geometry itself
A ruler tool measures distance directly on the map, and layers toggle what's displayed, so the surfaces behind a result can be checked visually, not just taken on faith.
- 04
Every past evaluation, one click back
History holds every obstruction evaluation already run for the airport, so answering a new question doesn't mean starting over from a blank map.
Built on the regulation
The citation, implemented
- 14 CFR Part 77
§77.19 civil airport imaginary surfaces define the approach, transitional, horizontal, conical, and primary surfaces around a runway. An evaluation here checks an object against all of them in the same pass, computed from the airport's own FAA survey coordinates rather than a rough guess off the base imagery.
The benefit
What it automates
Every surface, one pass
An object gets checked against every Part 77 surface for the runway at once, instead of the same geometry re-run surface by surface.
FAA survey coordinates, not a satellite guess
Distances and surface boundaries come from the airport's actual FAA survey coordinates, so a result near a boundary is something to trust, not a rounding error.
The map explains the result, not just the verdict
Ruler and layer tools let anyone check the geometry behind an evaluation directly on the map instead of taking the outcome on faith.
Related
Works alongside
FAQ
Straight answers
Which surfaces does an evaluation check?
The imaginary surfaces 14 CFR §77.19 defines around a civil airport's runway (approach, transitional, horizontal, conical, and the primary surface), checked together instead of one at a time.
How is the object's location set?
Tap its spot on the satellite map, or open the page on a phone while standing next to the object itself, then note its height above the ground.
How accurate are the distances?
They're computed from the airport's own FAA survey coordinates rather than a flattened estimate off the satellite image, with a ruler tool to check the geometry directly on the map.
Can I see past evaluations?
Yes. History holds every evaluation already run for the airport, so nothing has to be redone to check what was found before.