SOLAR SHADOWINGAN OPPORTUNITY FOR SURVEYORS

Rod Deakin

Simple Shadow Diagrams:

Buildings BLUE; Shadows RED

Constructing Shadow Diagrams

Basic Requirements:• Dimensions of building including height

above natural surface.• Reduced level of natural surface.• Profile of natural surface in the direction

of the shadow.• Table of Sun Azimuths and Altitudes.• Trigonometry (sine, cosine, tangent!)

• CORRECT ORIENTATION• Pencil, paper, protractor, scale rule and

parallel ruler (?)

Orientation of Shadow Diagrams

Correct Orientation means that all bearings should be TRUE BEARINGS – clockwise angles from TRUE NORTH.

Azimuth = True Bearing

There is a confusion of Norths:

True North; Approximate True North; Grid North; Magnetic North; Arbitrary North; AMG North; MGA North; Zone55 North; Litho; and just plain old North.

Map projection relationships

True North (TN) is direction of meridian

Grid North (GN) is direction of central meridian of zone

θ = plane bearing

β = grid bearing

γ = grid convergence

δ = arc-to-chord

Azimuth = β + γ

λ

φ

cen

tra

l

merid

ian

GNT N

γ

s

L

θβ

projected geodesic

plan e

distan ce

1λ2

1

φ 2

P2

P1

N

N

2

1

E

E

2

1

δ12

True, Grid and Magnetic North

Relationships between north points need to be clear.

Magnetic Declination varies; so date required.

TN GN

MN

DeclinationMagnetic

GridConvergence

Diagram for point in Victoria, west of central meridian of zone

TNMN

BARKLY STREET

98° 30′

8° 24′ (1884)

TRUE

90° 06′

98° 30′

Magnetic Declination

Survey Practice Handbook

Sun Azimuth & Elevation(spherical trig and Star Almanac for Land Surveyors)

Sun Azimuth & Elevation(low precision prediction formula)

Meeus, J. (1998) “Astronomical Algorithms”, 2nd edition,Willmann-Bell, Inc., Richmond, Virginia, USA.

Meeus, J. (1985) “Astronomical Formulae for Calculators”, 3rd edition,Willmann-Bell, Inc., Richmond, Virginia, USA.

Sun Azimuth & Elevation

JPL HORIZONS

JPL HORIZONS: THE GOLD STANDARD

City of Melbourne

Yarra River, 11am, 22 June

City of Melbourne

Yarra River, 12 pm, 22 June

City of Melbourne

Yarra River, 1 pm, 22 June

City of Melbourne

Yarra River, 2 pm, 22 June

The Sun in the sky

(one year)

Analemma with Parthenon (Athens)

The Sun at the same time of day (12:28:16 UT+2) over the course of a year (Jan 12, 2002 – Dec 21,2002).

41 multiple exposures + 1 foreground exposure.

http://perseus.gr/Astro-Solar-Analemma.htm

City of Melbourne

Yarra River, 2 pm, 22 June