Calgary Board of Education

 
Environmental Learning

Native Plant Park

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Phases

Map of Phase III

Map of Phase III
The Human Sundial
Info Centre
Phase I & II
Phase III

Installing an Analemmatic Sundial

1. Determine the desired size of the sundial. The size will depend on the height of the people who will be using it. For an elementary school, we used an ellipse with a major axis of 2.25 metres - this works well for people with a height up to 1.6m. For taller people, the ellipse should be larger.

2. Calculate the x-y positions for the times on the ellipse, according to the formulas in the Appendix. The y-axis will be oriented north-south, the x-axis east-west.

3.Calculate the gnomon positions for each month, using the formula in the Appendix. The gnomon positions are located along the y-axis.

4. Draw the time and gnomon positions onto a template of heavy paper or plastic.

5. Determine the direction of north at the sundial site. A compass direction will not be accurate enough. The easiest way is to locate the shadow direction of a vertical object at solar noon by hanging a plumb line and marking its shadow on the pavement. This shadow will point due north. To find out when solar noon will occur, use the Sunangle website (www.susdesign.com/sunangle/). By inputting the particulars of latitude, longitude, and date, the website will then calculate the precise clock time of solar noon.

6. Transfer the time and gnomon position from the template onto the pavement.

Click here to see how to tell time with the sun only (PDF)

Details of the Analemmatic Sundial

Installing an Analemmatic Sundial

Equation of Time

References

Appendix