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Error Analysis of a Monumental Garden Variety Sundial Roger Bailey NASS 2009 Portland, OR ©Phil Palies.

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Presentation on theme: "Error Analysis of a Monumental Garden Variety Sundial Roger Bailey NASS 2009 Portland, OR ©Phil Palies."— Presentation transcript:

1 Error Analysis of a Monumental Garden Variety Sundial Roger Bailey NASS 2009 Portland, OR ©Phil Palies

2 Questions for NASS Registrar How do I register this sundial? Now under construction at Soap Lake WA Is there a sundial expert we can consult? Artists rendering from website Is this a Sundial?

3 Response from NASS Expert A sundial is an instrument designed to tell time The gnomon must be straight and at the correct angle The hour lines depend on the location and are different for each hour. What is now cast in bronze & cement? Artists rendering from website Data & pictures required On angles, size, location,etc

4 Hour Lines for 47.4º Latitude


6 Hour Lines for 37º Latitude

7 Shadow Lengths through the Seasons

8 Orientation Use the suns shadow to determine the orientation Table of times when the sun is south, east or west Spreadsheet corrected for EQT and Longitude Date DOY Declination EQT EQT º Noon South Sun West Sun East 16-May :54:19 17:39:36 8:09:01 17-May :54:20 17:38:39 8:10:02 18-May :54:23 17:37:43 8:11:02 19-May :54:25 17:36:49 8:12:02 20-May :54:29 17:35:57 8:13:00 21-May :54:33 17:35:07 8:13:58 22-May :54:37 17:34:19 8:14:56 23-May :54:42 17:33:32 8:15:52 24-May :54:48 17:32:48 8:16:48 25-May :54:54 17:32:05 8:17:42 26-May :55:00 17:31:24 8:18:36

9 Soap Lake, WA MineralMilligrams/Liter Sodium5760 Bicarbonate2480 Sulfate2540 Carbonate3840 Chloride2290 Potassium 504 Organic nitrogen 0.9 Fluoride 7.2 Ortho-phosphate 6.3 Nitrate 0.7 Calcium 2.5 Magnesium 2.9

10 Soap Lake Garden Club

11 Healing Waters Spa treatment like the thermal mineral baths in Europe Bathing in the alkali waters, soaking in the mud, cures people afflicted with Buerger's disease and other ailments [ GC1DJWD

12 Modern Spa Treatment Spa treatment is now an sensual indulgent luxury You deserve it Hot rocks Hot oil massage Aromatherapy Soap Lake missed the market Calling the healing Waters a new focus

13 Concept Centre of Interest for Soap Lake Build it and they will come Theme: Calling the healing waters Reflects ethnic and historical themes Mighty winger warrior protecting and comforting maiden with catch basin for healing waters

14 Installation of basalt columns Angles and offsets are obvious

15 Error Analysis Sculpture is a poor sundial A worst case scenario Feathered arm at ~37º but curved and offset from center Base at ~30º is offset vertically Various parts of the structure cast shadows on the hour lines on the base

16 Error Analysis

17 Error Minimazation Considerations Users: –People going to the park to enjoy the beach and water. –Good time not regimented time Season: –Summer not winter –Spring and fall if the weather is good Time –9 AM to 5 PM Summer –Peak mid-afternoon Impression: –Form follows fashion, not function –Looking good is most important

18 Sundial Considerations Can the sundial work? –giving an impression of time –When most people will see it Design for summer, solar noon +/- four hours Design based on a point gnomon, the tip of the feather Calculate design for 47º –Hold the gnomon tip fixed –Move the base intersection to 37º design Calculate shadow planes for 37º at various times of day and declinations of the year Choose the best compromise considering use Design is fit for purpose

19 Shadow Plane Analysis The 37º gnomon has a shadow plane Shadow plane intersects the base at a specific angle Shadow angle (SA) varies through the seasons Tan SA= Sin G x Sin Az/ Cos G x Tan Alt +Cos G x Cos Az –giving an impression of time –When most people will see it Spreadsheet used to calculate altitude, azimith and the declination, latitude and time angle Sin Alt = Sin Dec x Sin Lat + Cos Dec x Cos Lat x Cos t Shadow angle calculated from altitude, azimuth and gnomon angle Plotted on sundial design by Zon 2000 with DeltaCad "Error Analysis of The Horizontal Sundial-I" Lauoesch & Edinger, NASS Compendium 2-3, Sept 95


21 Shadow Plane Analysis



24 Artists David Govedere Sculptor Keith Powell Artist Concept accepted in 1994 Bronze sculpture cast in 2003 ©Phil Palies


26 Finished Sculpture Curved offset feathered arm as gnomon Hour Lines and Posts Solar Noon +/- four hours 9AM to 5 PM © Raymond Gravelle

27 Time Check XII XII is XI solar Hour Line band = post widths Tip of shadow in the middle of hour band Curve and offset of feathered arm is obvious Time check OK © Raymond Gravelle

28 Time Check III III solar II Again the tip of the feathered arm tells the time Hour lines diverging Time check OK © Raymond Gravelle

29 Summary Objectives met Sculpture looks good, an excellent focal point on the Soap Lake beach Sundial is fit for purpose Time indications OK in the summer 9AM to 5 PM © Raymond Gravelle

30 Toolbox NASS Compendium & Presentations Error Analysis of The Horizontal Sundial" Lauoesch & Edinger Error Analysis of Garden Variety Sundials Software: Zon 2000, DeltaCad, Excel Spreadsheets: Error Analysis Garden Variety Sundials Shadow Angles Meridians and Prime Vertical

31 Acknowledgements Raymond Gravelle: Challenge, data, photographs, patience Larry McDavid: Asking the right questions Phil Palios Philthy Photography Photos of the dedication ceremony at

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