FAA FAR 77 tool warning: “Airport reference point and runway end points are significantly different” with validated geometry

[CarieErnst_KYTC]

Hello,

I am running the FAA FAR 77 tool in ArcGIS Pro (version 3.5) and consistently receive the warning:

“The airport reference point and the runway end points are significantly different. This may cause the obstruction identification surfaces to generate incorrectly.”

However, I have validated the geometry and cannot identify any spatial inconsistency:

• Single runway airport

• Runway length: 3849.97 ft

• ARP to Runway End A: 1924.70 ft

• ARP to Runway End B: 1925.27 ft

• Difference from midpoint: ~0.57 ft

• Data projected to WKID 3089 (Kentucky Single Zone, US Feet) Vertical WKID 6360

• Map coordinate system matches dataset

• No displaced thresholds

• Only one runway feature

• Runway centerline is a simple 2-vertex line

• Airport elevation parameter correctly supplied (1040 ft)

• Runway end elevations are consistent

• No joins or definition queries

• All features exported into a clean file geodatabase

The generated OIS surfaces appear correct and centered.

Given the above, I am trying to determine:

1. What tolerance threshold triggers this warning?

2. Is the check purely horizontal, or does it include vertical comparison?

3. Is this known to occur due to internal reprojection or rounding?

4. Can this warning safely be ignored when geometry is validated?

Any insight into the internal validation logic would be appreciated.

Thank you.

[KiyoshiYamashita]

Hi! Apologies for answering your question with a question... but do your Airport Reference Point and Runway End features all have z-values?

Usually, this warning is triggered when the airfield elevation (which can come from the ARP feature) and the runway end elevation (which can come from the Runway End features) are very different.  Since some of the part 77 surfaces are constructed relative to these different elevations, if they are drastically different, the tool can have trouble making sure all the surfaces connect appropriately.

If you are able to share your input data, I can tell you more specifically why you received that warning.  You can attach a zipped GDB here or send to aero@esri.com (attn: Kiyoshi Y) if unable to share publicly.

[CarieErnst_KYTC]

Hi Kiyoshi,

Yes, the ARP does have z values. I will send you a FGDB and appreciate any insight you can provide. 

[Jaimie_Nevins]

@CarieErnst_KYTC  did you get a response and a solution to this error?  I am experiencing the same thing when I run my part 77 tool...but only for a few airports.  The data formats are exactly the same, and resulting surface layers look correct (just like your results).  So I'm curious if this is a bug or an actual problem.  Thanks!

[KYTCGIS]

Hi Jamie, I'm just now circling back and realizing I had responses. I did not find a solution but intend to reach out to Kiyoshi and will let you know if we uncover anything. Did you find a solution yet?