Kurs gjældende Værdi af Compassets Deviation corrigeredes 
den i Grader udtrykte observerede Vindretning til den rig- 
tige. misvisende. 
Med disse Data udførtes Beregningen af den sande 
Vindhastighed og den misvisende virkelige Vindretning paa 
følgende grafiske Maade. 
Paa “Kobbel-Rosen,” af hvilken Fig. 9 viser det cen- 
trale Parti gjengivet, kun med Udeladelse af de i Origi- 
nalen optrukne Streger for hver enkelt Grad udenfor Af- 
29 
deviation of the compass found for the course of the vessel 
(ship’s head by C.), the observed direction of the wind, ex- 
pressed in degrees, was corrected to the true magnetic course. 
With these data, the computation of the true velocity 
of the wind and the true magnetic direction of the wind 
was made diagrammatically, as follows: — 
On the Course and Distance Card, of which the central 
portion is represented in Fig. 9, with the omission only of 
the radial lines drawn for each separate degree beyond 
Centrum af Rosen 
afmerkedes paa dette, og Nord-Syd-Linien blev optrukket. 
Det bidrager til Nøjagtighed at optrække ogsaa Øst-Vest- 
standen 5, lagdes et Stykke Kalkerpapir. 
Linien gjennem Centrum. Fra Centrum afsattes 1) Skibets 
(misvisende) Kurs og Fart, og Endepunktet paa denne 
Linie merkedes; 2) den observerede Vinds (misvisende) 
Retning og Hastighed, og Endepunktet merkedes. Kalker- 
papiret flyttedes nu saaledes, at det første Punkt faldt i 
Rosens Centrum, og de optrukne Nord-Syd- og Øst-Vest- 
Linier orienteredes parallel med Rosens tilsvarende verti- 
cale og horizontale Linier. Punktet No. 2 angiver da den 
virkelige (misvisende) Vindretning og Hastighed. 
Ved Hjelp af Misvisningen reduceredes den saaledes 
fundne, i hele Gader udtrykte, misvisende Vindretning til 
sand Vindretning. 
Den geometriske Construction kunde naturligvis ud- 
føres med de retvisende Kurser og Vindretninger eller med 
de observerede, i hvilket sidste Tilfælde man til Slutning 
havde at anbringe den totale Compas-Fejl som Correction. 
the distance 5, was laid a piece of transparent paper. The 
centre of the card was marked on this paper, and the 
North-South diameter-line drawn. Additional accuracy 
is secured by also drawing the East-West diameter-line. 
From the centre was laid off 1) the ship’s magnetic course 
and speed, the terminal point of this line being marked; 
2) the magnetic direction and velocity of the observed wind, 
the terminal point of the line being marked. The trans- 
parent paper was now moved so that the point first marked 
was made to coineide with the centre of the card, and the 
North-South and East-West lines were parallel with the 
vertical and horizontal lines of the card. Point 2 would then 
indicate the true (magnetic) direction and the velocity of 
the wind. 
By means of the variation, the magnetic direction of 
the wind, thus found and expressed in whole degrees, was 
reduced to the true direction. 
The geometrical construction could of course be made 
with the true courses and directions of the wind, or with 
those observed; in the latter case, the total compass-error 
had to be applied as a correction. I preferred the method 
