DEFINITIONS FOR ZW2000

Definitions

phi

 latitude of the place of the dial. -90° <= phi <= 90°,
northern latitude positive, southern latitude negative.
g

 length of (pin) gnomon perpendicular to the dial's plane.
The tip of the gnomon is the shadow casting point.
1 < g < 100.
i

 inclination of the plane: the zenith distance of the endpoint of the (pin) gnomon.
0° <= i < 180°.
d

 declination of the plane: azimuth of the gnomon: south = 0°, positive to west, negative to east.
-180° <= d <= 180°.

SM

 standard meridian of time zone. Greenwich = 0°, positive to west, negative to east.
-180° <= SM <= 180°.
LM

 local meridian. Greenwich = 0°, positive to west, negative to east.
-180° <= LM <= 180°.

LC

 longitude correction LC = SM - LM.
E

 equation of time in degrees. In november E is positive.
Conversion minutes of time into degrees: 1 minute = 0.25 degrees.
v

 height of a style, parallel to the earth axis.
-90° <= v <= 90°.
b

 angle of substyle, measured from y-axis.
pos. is anti clockwise neg. is clockwise.
-180° <= b <= 180°.

ts

 hourangle of substyle. -180° <= ts <= 180°.

decl

 declination of the sun,
positive if sun in northern hemisphere, negative if sun in southern hemisphere.
-23.°5 <= decl <= 23.°5

t

 hourangle of the sun: noon = 0°, positive to west, negative to east.
-180° <= t <= 180°.
x, y

 coordinates of shadow point. Footpoint gnomon = 0,0. x to right, y upwards.
For horizontal dial x east, y north.

dn

 daynumber.
January first at 00:00:00 is daynumber 1.0 , at 12:00:00 is daynumber 1.5.
threads

 parallel to the plane and perpendicular above 0,0 at distance height.
If rotation = 0 thread-x parallel to x-axis, thread_y parallel to y-axis.
rotation

 angle of rotation of the threads for bifilar dial. -180 <= rotation <= 180.
rotation positive is anti clockwise, rotation negative is clockwise
height_x
height_y

 perpendicular distance from pount 0,0 to threads.
1 < height < 100.

refraction
index

 for water the refraction index is about 1.333

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