Stonehenge
Sighting the Sun
by Clive Ruggles and Amanda Chadburn
Supplementary online materials
All-round horizon profiles
General notes
- The pictures show the entire horizon profile from each location as generated from Digital Terrain Model data by Andrew Smith of the University of Adelaide using his program HORIZON.
- Specifically, the results are calculated from a composite of 2m composite LiDAR-based DTM (May 2019 release) from DEFRA, and Terrain 50 DTM (July 2020 release) from the Ordnance Survey. Fortunately, all the sites and their immediate surroundings were within the area covered by the DEFRA LiDAR survey (see this coverage map). Void areas were filled with the Terrain 50 data.
- In the case of the Durrington Walls profiles, the A345 road and its embankment, together with the old A345 road, have been digitally removed from the DTM.
- These profiles do not take into account that parts of the horizon may be, or have been, blocked by stones (e.g. sarsen uprights as viewed from the centre of Stonehenge) or by intervening vegetation.
- Each profile is available in both JPG and PNG format. The PNG files are larger and will take longer to download.
- Azimuths and altitudes are indicated using 1° grids, with thicker lines at 5° intervals. The azimuths are labelled; altitudes (unlabelled) run upwards from 0°. Lines of declination, labelled, are shown at 5° intervals. (See the Glossary for the meanings of terms.)
- The darker yellow lines indicate the rising and setting paths of the sun at the solstices (lower line, December solstice; upper lines, June solstice). The lighter yellow lines indicate its rising and setting path at the equinoxes. The red lines indicate the rising and setting paths of the moon at the major standstill limits (see p. 45, note 26), i.e. at its northernmost and southernmost extremes. The green lines indicate its paths at the minor standstill limits (see p. 45, note 28). The solar and lunar lines are calculated for 2400 BC.
- The red and green lunar lines are not included in the Durrington profiles.
Example: all-round horizon profile from the centre of Stonehenge
- Where included, the accompanying PDF files show the horizon altitude (marked as ‘elevation’—see Glossary, pp. 186–7) and distance in each direction, the latter displayed logarithmically. The horizontal scale is marked at 5° intervals, with the cardinal and intercardinal directions (N = 0°, NE = 45°, etc — see Explainers pp. 183–4) indicated.
- Where included, the ‘datasets’ files show the dataset coverage for a given profile: red indicates the areas covered by the 2m data and green the 50m data.
- Except where otherwise indicated, the observer’s eye level is taken to be 1.5m above the local terrain.
Stonehenge
Observing position: OSGB 412246 142194 (SU 12246 42194) (centre of stone circle)
There has been a great deal of confusion as to whether Sidbury Hill, 12.6km away, would form the horizon along Sightline 2 to the NE in the absence of intervening vegetation and buildings (see pp. 137; 148, note 10). Our calculations show that this was not the case. For an observer height of 1.5m, the summit of Sidbury Hill (azimuth 48.3°) has an an altitude (not accounting for terrestrial refraction) of +0.48°, which is just below the altitude of the ridgetop at SU 144 439, 3.0 km away.
To confirm this, Andrew has also calculated this profile with the ground level raised by 9m (giving an effective observer height of 10.5m) and with the position of Sidbury Hill marked:
When the part around az. 48° is magnified with increased resolution, the top of Sidbury Hill can clearly be seen in the distance above the closer ridge (JPG, PNG). A similar picture generated with the ground level raised by 6m (effective observer height 7.5m) shows Sidbury Hill just starting to come into view (JPG, PNG).
All this said, if the closer ridge were clear of vegetation but trees were growing on Sidbury Hill, then the tops of those distant trees might well be visible.
Woodhenge
Observing position: OSGB 415068 143376 (SU 15068 43776) (centre of rings)
All-round horizon profile from the centre of Woodhenge
Durrington Walls South Circle
Given minor inconsistencies in and between the available excavation, survey and GIS data, we estimate the geometrical centre of the South Circle to be somewhere between 415140.8 143651.4 (‘SC1’) and 415139.8 143651.1 (‘SC2’), while that of the centre of the Avenue at its south-eastern end by the cliff is somewhere between 415276.0 143551.2 (‘AE1’) and 415276.0 143549.9 (‘AE2’).
Observing position assumed: OSGB 415140 143651 (SU 15140 43651). The elevation is taken as 83.9m ASL, this being today’s ground level within the circle at the foot of the A345 embankment. (The archaeological evidence indicates that the original ground level was about 1.5m lower, which compensates for the 1.5m eye height of a prehistoric observer.)
The following profiles use ‘fake posts’ to mark the positions of AE1 and AE2 as seen from SC1 and SC2 respectively. These do NOT represent actual posts.
The following profiles include lines of ‘fake posts’ in the foreground that were placed at points along georeferenced archaeological features in order to ensure the accuracy of the graphical reconstruction shown in Fig 6.13. These do NOT represent actual posts.
- Profile with ‘fake posts’ marking the outer edge of the ‘road’ (trampled flint) surface and inner edge of the ditch (see p. 94), JPG, PNG;
- Profile with ‘fake posts’ marking the outer edge of the ditch and the inner edge of the bank, JPG, PNG;
- Profile with ‘fake posts’ marking the outer edge of the bank, JPG, PNG;
- Profile with all three lines of ‘fake posts’ as above, JPG, PNG;
- The taller posts (one in each line) indicate the position of the gatehouses.
All-round horizon profile from Durrington South Circle, with lines of ‘fake posts’ marking the edges of the ‘road’ (trampled flint) surface and the flanking ditches and banks. (The posts of the monument itself in the foreground are not shown.)
Durrington Avenue (Sightline 7 is NW-wards along the avenue towards Durrington South Circle)
Observing position assumed: OSGB 415276 143551 (SU 15276 43551)
The following profiles include lines of ‘fake posts’ in the foreground that were placed at points along georeferenced archaeological features in order to ensure the accuracy of the graphical reconstruction shown in Fig 6.11. These do NOT represent actual posts.
- Profile with ‘fake posts’ marking the outer edge of the ‘road’ (trampled flint) surface and inner edge of the ditch (see p. 94), JPG, PNG;
- Profile with ‘fake posts’ marking the outer edge of the ditch and the inner edge of the bank, JPG, PNG;
- Profile with ‘fake posts’ marking the outer edge of the bank, JPG, PNG;
- Profile with all three lines of ‘fake posts’ as above, JPG, PNG;
- The taller posts (one in each line) indicate the position of the gatehouses.
All-round horizon profile from the SE end of the Durrington Avenue, with lines of ‘fake posts’ marking the edges of the ‘road’ (trampled flint) surface and the flanking ditches and banks.
Other supplementary on-line materials