A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Ducruy Jacques
Date: 2015 Aug 4, 06:27 -0700
Another little observation : it seems there are two versions of "methode du meridien estimé" :
1) english version, with versine formula : vers (L-D) = vers DZ - cos D cos L vers HA ;
2) french version, with calculation of latitude by the formula of "right angled triangle"(as Borda' double altitude method).
In my opinion, the english version is only valable between the "limites of circumméridiennes", as we said in french. The french method seems more "tolerant". But it seems that, in France, this method had only a theoric interest.