An overview of tools to help archaeoastronomy in the field and at the desk.
The link (on slide 10) to download the HeyWhatsThat skyline csv file needs to be changed to: http://www.heywhatsthat.com/api/horizon.csv?id=<HWT-ID>&resolution=.125&keep=1
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Skyline, azimuth and altitude tools for archaeoastronomy
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. 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. Part 1
• Tools to determine skyline
• Apps for augmented reality - theodolite
http://tinyurl.com/j8myvfb
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. 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. 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
10. HeyWhatsThat skyline in Stellarium
http://tinyurl.com/j8myvfb
http://www.heywhatsthat.com/api/horizon.csv?id=<HWT-ID>&resolution=.125
11. HeyWhatsThat viewshed in Google Earth
http://tinyurl.com/j8myvfb
Common visibility in Google Earth
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
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. Based on 3D model
VRML and OS map
http://tinyurl.com/j8myvfb
Video by Victor Reijs: NAM2003
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
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
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. Part 2
• Tools to determine skyline
• Apps for augmented reality - theodolite
http://tinyurl.com/j8myvfb
29. Error in averaged azimuth
(four positions)
http://tinyurl.com/j8myvfb
30. Error in averaged altitude
(four positions)
http://tinyurl.com/j8myvfb
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. 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
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