Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Skyline, azimuth and altitude tools for archaeoastronomy

548 views

Published on

An overview of tools to help archaeoastronomy in the field and at the desk.

Published in: Self Improvement
  • Be the first to comment

  • Be the first to like this

Skyline, azimuth and altitude tools for archaeoastronomy

  1. 1. Skyline tools and theodolite Apps for archaeoastronomy Skills, Sep. 14th, 2016 Victor Reijs victor.reijs@archaeocosmology.org http://www.archaeocosmology.org/eng/skylineprofilescomparing.htm
  2. 2. Knowing the (apparent) altitude is essential for latitudes >40° Parameter (device) Parameter StDev in deg Impact Resulting declination StDev in deg Latitude (GPS) 0.01 0.5 0.005 Altitude (clinometer) 0.2 0.9 0.18 Azimuth (compass) 0.5 0.5 0.25 Resulting 0.31 • At average altitude of 1° • At average latitude of 53° • Azimuth between 30° and 150° http://tinyurl.com/j8myvfb
  3. 3. Part 1 • Tools to determine skyline • Apps for augmented reality - theodolite http://tinyurl.com/j8myvfb
  4. 4. Tools to determine skyline • Desk based research – height grid – 3D model • Field based research – photometry – theodolite (compass and clinometer) http://tinyurl.com/j8myvfb
  5. 5. Some height grid based tools • OS map – Manual (Alexander Thom) – Horizon standalone programme since 2002 (Andrew Smith) • SRTM (Shuttle Radar Topography Mission) grid – 90m resolution • HeyWhatsThat Web service since 2000 (Michael Kosowsky) • Horizon standalone programme since 2002 (Andrew Smith) • SyntH privately run service since 2011 (Fernando Patat) – 30m resolution – SyntH privately run service since 2015 (Fernando Patat) http://tinyurl.com/j8myvfb
  6. 6. Ins and outs of height grid • Can be low resolution • Large errors for nearby objects • Can have gaps/voids in the grids None of the tools depict the documented SRTM voids (height value -32768) • Does not include plants/constructions at horizon • Fixed position http://tinyurl.com/j8myvfb
  7. 7. Comparing different skyline programs http://tinyurl.com/j8myvfb Theodolite SyntH SRTM 30m Horizon SRTM 90m HWT, SyntH SRTM 90m
  8. 8. Missing grid data SRTM 90m SRTM Missing grid data http://tinyurl.com/j8myvfb Photo by M.J. Zawaski and J.McKim Malville
  9. 9. Some additional features of grid based tools http://tinyurl.com/j8myvfb
  10. 10. HeyWhatsThat skyline in Stellarium http://tinyurl.com/j8myvfb http://www.heywhatsthat.com/api/horizon.csv?id=<HWT-ID>&resolution=.125
  11. 11. HeyWhatsThat viewshed in Google Earth http://tinyurl.com/j8myvfb Common visibility in Google Earth
  12. 12. Ins and outs of 3D model • Based on height grids • To include terrestrial refraction can be cumbersome • Flexible position http://tinyurl.com/j8myvfb
  13. 13. 13 Ring of Brodgar, Watchstone, Standing stones of Stenness, Barnhouse Stone, etc. Based on 3D model VRML and OS map http://tinyurl.com/j8myvfb Video by Victor Reijs: NAM2003
  14. 14. Based on 3D model VRML and OS map http://tinyurl.com/j8myvfb Video by Victor Reijs: NAM2003
  15. 15. Ins and outs of photometry • Stitching-, level- and/or lens distortion errors • Possible influence of atmospheric haze • Includes plants/constructions at horizon • Fixed position http://tinyurl.com/j8myvfb
  16. 16. Based on photometry http://tinyurl.com/j8myvfb SRTM Photo Photo by Michael Wilson: http://mega-what.com/
  17. 17. Ins and outs of on theodolite • Time consuming • Depending on weather • Possible influence of atmospheric haze • Fixed position • Is quite accurate (seen as benchmark) http://tinyurl.com/j8myvfb
  18. 18. Based on theodolite Theodolite SRTM http://tinyurl.com/j8myvfb Theodolite data by Michael Wilson : http://mega-what.com/
  19. 19. Conclusions Part 1 • Know your tools! • The higher the resolution the better • A combination of skyline tools is essential • Provide constructive feedback to tool builders • Verifying with reality is essential http://tinyurl.com/j8myvfb
  20. 20. Part 2 • Tools to determine skyline • Apps for augmented reality - theodolite http://tinyurl.com/j8myvfb
  21. 21. Altitude - clinometer http://tinyurl.com/j8myvfb
  22. 22. Azimuth - compass http://tinyurl.com/j8myvfb
  23. 23. Augmented reality - theodolite http://tinyurl.com/j8myvfb
  24. 24. SunSurveyor http://tinyurl.com/j8myvfb
  25. 25. By Alison Chester-Lambert: 25 June 2014 Portrait position The Circus, Bath: summer solstice Summer solstice path Sun’s position on 25/6/2014
  26. 26. Difference in measured azimuth Portrait up and down http://tinyurl.com/j8myvfb
  27. 27. Landscape position The Circus, Bath: summer solstice http://tinyurl.com/j8myvfb Summer solstice path Sun’s position on 25/6/2014
  28. 28. Difference in measured azimuth Landscape up and down http://tinyurl.com/j8myvfb
  29. 29. Error in averaged azimuth (four positions) http://tinyurl.com/j8myvfb
  30. 30. Error in averaged altitude (four positions) http://tinyurl.com/j8myvfb
  31. 31. Conclusions Part 2 • Azimuth error does not depend on App, but on device (soft and hard iron influence) tested: Samsung Tab2, iPad Air 2 and iPhone 6s Plus • Azimuth StDev of my Samsung tablet (>2.8°) is much larger than compass (>0.5°) • Altitude StDev of my Samsung tablet (>0.2°) is somewhat larger than clinometer (0.2°) • For nearby targets: watch out for parallax error camera is not in middle of device http://tinyurl.com/j8myvfb
  32. 32. Conclusions 1. Getting a sustainable skyline (web) service might be important for archaeoastronomy discipline! 2. Smart devices are not yet (mid 2016) mature enough for accurate azimuth measurements. Provide constructive feedback to tool builders http://tinyurl.com/j8myvfb
  33. 33. Questions? http://tinyurl.com/j8myvfb
  34. 34. Selected of sources Kosowsky, Michael. 2012.'HeyWhatsThat', in http://www.heywhatsthat.com/ [accessed 10 March 2012]. Patat, Fernando. 2011. 'Horizon synthesis for archaeo-astronomical purposes', Astronomische Nachrichten, Vol 332: pp. 743-49. Reijs, Victor M.M. 2001.'The reappearing sun at Orkney', in http://www.iol.ie/~geniet/maeshowe/eng/flashing.htm [accessed 4 March 2012]. Reijs, Victor M.M. 2007.'Refraction: Refraction calculation', in http://ireland.iol.ie/~geniet/eng/refract.htm#Calculated [accessed 2 July 2012]. Reijs, Victor M.M., and Kris Winer. 2016.'Calibration of magnetometer', github, in https://github.com/kriswiner/MPU-9250/issues/42 [accessed 10 September 2016]. Schaefer, Brad E. 2000. 'New methods and techniques for historical astronomy and archaeoastronomy ', Archaeoastronomy: The journal of astronomy in culture, Vol XV: pp. 121-35. Smith, Andrew. 2014.'Horizon', in http://www.agksmith.net/horizon/ [accessed 10 September 2016]. Thom, Alexander. 1971. Megalithic lunar observatories (Oxford University Press). Wilson, Michael. 2014.'¡¿ Mega-WHAT ?!: Megalithic horizon calendars, that's What', in http://mega- what.com/index.html [accessed 16 December 2014]. Zawaski, M.J., and J.McKim Malville. 2007 to 2008. 'An astronomical survey of major Inca sites in Peru', Archaeoastronomy: The journal of astronomy in culture, Vol XXI: pp. 20-38. http://tinyurl.com/j8myvfb

×