Rainwater Harvesting for Drylands and Beyond by Brad Lancaster

Winter-Solstice Shadow Ratio & Azimuth Table

Determine objects’ shadow lengths and direction on the day with the longest shadows of the year (the winter solstice) using the following table of shadow ratios and sun’s azimuth angles for your latitude.

Use the ratio 1 : x to get the length of the shadow cast by an object (tree, cistern, house) for each foot (or meter) of height. Multiply the height of the object (in feet or meters) by x to get the length of the shadow (in the same units of measurement).

To get the direction of the shadow cast by an object, look at the Azimuth angle—the angle of the sun’s location east or west of True South in the northern hemisphere or of True North in the southern hemisphere. Note that when the position of the sun is to the east, it will cast a shadow to the west of any object. (See figures below the table for examples, and the “Integrated Design Pattern Five: Maintaining Winter Sun Exposure” section of Rainwater Harvesting for Drylands and Beyond, Volume 1, 2nd Edition, for still more examples, explanation, information, and tools.)

Sun Angle Chart Expanded 130206 p1

Sun Angle Chart Expanded 130206 p2

Sun Angle Chart Expanded 130206 p3a

For more examples, explanation, and information on how to use the this table and other passive solar design tools, see Integrated Design Pattern Five: Maintaining Winter Sun Exposure section of Rainwater Harvesting for Drylands and Beyond, Volume 1, 2nd Edition, by Brad Lancaster.

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Umbrella Newsletter

The Umbrella: Winter 2019/2020

THE UMBRELLA: A catch-all of resources, events, media, and more from Brad Lancaster   Rain Planting E-BOOK now available! Rainwater Harvesting for Drylands and Beyond, Volume 1, 3rd Edition now available in E-BOOK format Plant the Rain gifts Get holidays gifts that spread the word and practice on how we can make the world a […]

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