## 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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