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

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

7. Comparing different skyline programs
http://tinyurl.com/j8myvfb
Theodolite
SyntH
SRTM 30m
Horizon
SRTM 90m
HWT, SyntH
SRTM 90m

8. Missing grid data
SRTM 90m
SRTM
Missing grid data
http://tinyurl.com/j8myvfb
Photo by M.J. Zawaski and J.McKim Malville

9. Some additional features of
grid based tools
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

16. Based on photometry
http://tinyurl.com/j8myvfb
SRTM
Photo
Photo by Michael Wilson: http://mega-what.com/

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. Based on theodolite
Theodolite
SRTM
http://tinyurl.com/j8myvfb
Theodolite data by Michael Wilson : http://mega-what.com/

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

21. Altitude - clinometer
http://tinyurl.com/j8myvfb

22. Azimuth - compass
http://tinyurl.com/j8myvfb

23. Augmented reality - theodolite
http://tinyurl.com/j8myvfb

24. SunSurveyor
http://tinyurl.com/j8myvfb

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. Difference in measured azimuth
Portrait up and down
http://tinyurl.com/j8myvfb

27. Landscape position
The Circus, Bath: summer solstice
http://tinyurl.com/j8myvfb
Summer solstice
path
Sun’s position
on 25/6/2014

28. Difference in measured azimuth
Landscape up and down
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

33. Questions? 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