Max. dW = mp 
180 ? 
naar dy udtrykkes i Grader. 
2. Erv < w, kan e ikke blive saa stor som 90°, 
men %w kan blive 90°, i hvilket Tilfælde Maximum indtreeffer 
med en Værdi lig v, eller, naar dy regnes 1 Grader, 
Tt 
Max. dW =v 180 dy. 
3. Er v = w, er Betingelsen for Maximum, at sam- 
Hobe å = YOO og 4 = 209 g lninee =O og W=O, der 
er, naar Luften er ganske stille. Maximumsverdien af 
dW bliver = wdy = vdy. 
Er v = 0, bliver ‘ie = 0, eller Fejlen i den bereg- 
nede Vindhastighed uafhængig af Fejlen i den maalte Vind- 
retning. 
195 1 9 >4 ME dS Mer, Gy = 089. 
19:95 2 OS], WS, ty SO Wee GUY = O44 
Do 8 COS OSD med Vix Gy = O44 
Ved et Fartøj, som gjør 10 Mils Fart (v = 5), for- 
aarsager saaledes en Fejl af 5° (4/2 Streg) i den ombord 
observerede Vindretning en Fejl af kun henimod 0.5 Meter 
pr: Secund i den beregnede Vindhastighed. 
Den største Fejl, som overhovedet bevirkes i den be- 
regnede Vindhastighed af en Fejl i Bestemmelsen af Vin- 
dens Retning ombord, er alene afhængig af Skibets Fart, 
ikke af Vindens Hastighed. En Fejl af 1 Streg (11.925) 1 
y giver en Fejl af 0.1963 Meter Secund for 
Meters Fart, Skibet gjør i Secundet, eller med runde Tal 
en Fejl af '/;9 Meter pr. Sec. for hver Knobs Fart, Skibet 
gjør naar den ombord observerede Vindhastighed er 
større end Skibets Fart. Er den mindre, bliver Fejlen 
mindre i Forhold til den maalte Vindhastighed. 
pr. hver 
du es 
www 
DM — sin e 
= aa 
2 wv 
we I py? + » 2 
mv? se 
"Pas === 
w*t+ v Vw? I 0 
w Oo .« v 
=> Se = IY S eee 
re TE ve Vw? 
F . du : : v 
værdien af —— bliver lig =a 
dw w?—v 
Grader, 
Maximum haves, naar cosy = eller siny = 
da er ogsaa W = 
og sin U == sin 
å 9 
Maximums- 
W 
eller, naar du regnes 1 
. Mex, dm Ss == 
U= 
18 
TC 
Max. dW = VY 180 
assuming dy to be expressed in degrees. 
dy, 
2. Ifv < w, then e cannot amount to 90°, whereas 
w can reach 90°, in which case the maximum will have a 
value equal to v, or, expressing dy in degrees, 
V ax, — Kg . 
Max. dW =v 180 dy 
3. If v = w, the condition for reaching the maxi- 
mum is that e and w shall simultaneously equal 90°; y 
will then equal 0 and W 0, i.e. when the air is quite calm. 
The maximum value of dW = wdy = vdy. 
V 
Iti @ = @, thon Ad 
dy 
puted velocity of the wind independant of the error in the 
measured direction. 
or, the error in the com- 
bel, 9 >4A me dy =D, Va, Gy & O365, 
ho 7 DE=5 WO > dys OY Ves, Gly = OAL 
Me DEN OS] me", Wee, Gy = O44 
Hence, with a vessel running 10 miles an hour (v=5), 
an error of 5° (half a point) in the direction of the wind 
as observed on board, occasions an error of scarcely 0.5 
metre per second in the computed velocity. 
Generally, the greatest error that can result in the 
computed velocity of the wind from an error in the deter- 
mination of the direction of the wind as felt on board, 
solely dependent on the speed of the vessel, not on 
the velocity of the wind. An error of 1 point (11.025) in 
y entails an error of 0.1963 metre per second for every 
metre run by the ship in a second, or, 
is 
in round numbers, 
an error of one-tenth of a metre per second for every knot 
the vessel runs — provided the velocity of the wind as ob- 
if 
less, the error will diminish in proportion to the measured 
velocity of the wind. 
served on board be greater than the speed of the ship; 
v. SM Yy _ 
Ww 
v. Sin Y 
w? + v? —2 wv cosy 
: 2 wv 
The maximum is reached when cosy = ———, Or 
w + v* 
32. 2 32 
Ww?—v w*—v 
Sing = t 3 md vasen WY = === and sin u = 
— aD) 322 
WF-V Vu 
BD . w Å oO. v Th 
= smny = =) sin ES SIN Y = ==" e 
W Va I -wW Vw" 
: , CM ) 
maximum value of a will be equal to Fg OH Cone 
dw 2 
puting with dw in degrees, 
Max. du = EF 
