# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Message:αβγ
Message:abc
 Add Images & Files Posting Code: Name: Email:
Re: Contrail and Aircraft distance
From: Antoine Couëtte
Date: 2021 Oct 13, 07:40 -0700

Dear Lars,

Obviously we get the same results.

With "R" being the Earth Radius, "a" the Observer's altitude, "αthe A/C elevation above the true horizon, then the slant range "s" from A/C is given by the full formula as:

s / (R+a)  = -sinα + sqrt {  sin²α + [ (h-a)/(R+a)] * [2+[(h-a)/(R+a)] ]  }  (see one of the enclosures)

Hence with R = 6,378,137 m, a = 0 m : For α = 0.78° get s = 176.4 NM and α = 0.78° - (19/60)° = 0.466666...° get s = 192.2 NM.

Frank, you mentioned this site. If using their exact R value, i.e. 6,371,009 m, then I am deriving exactly the same values as they are publishing for all and any configuration.

And finally, for all, from a second enclosure, you will see how I accurately measured my "local horizon". T'was fun in that windy day.

Antoine M. "Kermit" Couëtte

antoine.m.couette[at]club-internet.fr

Browse Files

Drop Files

### Join NavList

 Name: (please, no nicknames or handles) Email:
 Do you want to receive all group messages by email? Yes No
You can also join by posting. Your first on-topic post automatically makes you a member.

### Posting Code

Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.
 Email:

### Email Settings

 Posting Code:

### Custom Index

 Subject: Author: Start date: (yyyymm dd) End date: (yyyymm dd)