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Stonehenge Hidden Landscape Project - Cursus/HeelStone solstitial alignments
by Simon at 16:02 26/11/11 (Blogs::Simon)
Worthy of further investigation, the Stonehenge Hidden Landscape Project (which is geophysing the entire World Heritage Site in 5 years) is reported to have discovered two large pits, one near either end of the Cursus.

Apparently these pits are aligned so that as seen from the Heelstone they mark the positions of sunrise and sunset on summer solstice.

I've yet to find the precise positions of the pits reported anywhere, but the sunrise one must be some way from the eastern end because the Lockyer azimuth crosses the Cursus some 400m from the eastern terminal.

I've indicated this on the following image from Google Earth.

The green line is the N-S meridian through Stonehenge, the purple one is Lockyer's azimuth from the Heelstone (ie the direction of summer solstice sunrise).

Google Earth view of where a Cursus pit ought to be (roughly) to mark summer solstice sunrise as seen from the Heelstone along Lockyer's azimuth.Google Earth view of where a Cursus pit ought to be (roughly) to mark summer solstice sunrise as seen from the Heelstone along Lockyer's azimuth. Click the attachment below for a larger version.

The article that drew this story to my attention was in The Independent.

Updated:

I dug out the 2010 interim report from the Hidden Landscape Project and screengrabbed the geophys of the west end of the Cursus.

In the image below the red line is a quick and dirty summer solstice sunset line drawn from the Heelstone on azimuth 310 to get an idea of where any sunset pit would have to be.

There are three candidate anomalies in the geophys plot near this line - one in the middle of the Cursus and one each just inside the north and south banks.

West end of Cursus with geophys overlay showing possible pit locationsWest end of Cursus with geophys overlay and rough summer solstice sunset line, showing possible pit locations. Click the attachment below for a larger version.

Update 2: Based on a screengrab from the video from the team (NB: there is no audio), it looks like the west pit is the one to the north, next to the north ditch. That would make it below the horizon as viewed from the Heelstone, so it'd need to be a huge post (if indeed it did hold a wooden post). The pits are apparently 5m across, depth unknown.

Hmm - the azimuth of the (assumed) west pit from the Heelstone is over 311, which is a degree north of where summer sunset is today.

That means the alignment must date from a time when the Earth's axial tilt was near its maximum of 24 21' (but we've got to assume my overlay of the preliminary geophys results is exactly right, which it may not be - wish there were OS grid refs of the pits available right now).

We *might* be looking at pits that were dug around 8000BC - around the same time as the mesolithic postholes in the car park.
--
simon

Attachments...
JPG image (153 K) Gogle Earth view of alignments showing where a Cursus pit ought to be (roughly)
JPG image (180 K) West end of cursus showing geophys overlay and rough summer solstice sunset line
<< Samhain/Imbolc Sunrise alignme... Winter Solstice Sunrise alignm... >>
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Stonehenge Hidden Landscape Project - Cursus/HeelStone solstitial alignments Simon - 16:02 26/11/11
- Deleted User Account - 21:02 26/11/11
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- Deleted User Account - 21:04 26/11/11
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- Deleted User Account - 21:06 26/11/11
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Re: Stonehenge Hidden Landscape Project - Cursus/HeelStone solstitial alignments Simon - 21:34 26/11/11
Good, innit :-)

Now check out St. Pete's square.
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simon

More accurate data (Re: Stonehenge Hidden Landscape Project - Cursus/HeelStone solstitial alignments) Simon - 19:50 29/11/11
Mike Pitts has recently published images from the Birmingham team showing the geophys upon which the Hidden Landscape Project has based its press release about the Cursus pits and their potential solstitial alignment.

I've georeferenced those images in QGIS along with the reference plan of Stonehenge from Cleal et al (1995) on an Ordnance Survey grid layer.

All that means is that I'm able to read off the OS Grid Refs directly.

HLP geophys and Cleal plan in QGISScreengrab of the relevant area from QGIS with the pits (and Heelstone) marked. (click for a larger version)

With the grid refs deduced, simple trig tells us the azimuths of the pits as seen from the Heelstone. We're working in an area less than 2km across so the OS grid is practically undistorted.

Azimuth calculations and diagram (click for larger version)

The azimuths come out as:

West pit from Heelstone: 311 45'
East pit from Heelstone: 50 17'

--
simon

Attachments...
JPG image (626 K) HLP geophys and Cleal reference plan in QGIS
PNG image (81 K) Azimuth calculations and diagram
Re: More accurate data (Re: Stonehenge Hidden Landscape Project - Cursus/HeelStone solstitial alignments) Jon Morris - 16:18 01/12/11
"Hmm - the azimuth of the (assumed) west pit from the Heelstone is over 311, which is a degree north of where summer sunset is today.

That means the alignment must date from a time when the Earth's axial tilt was near its maximum of 24 21' (but we've got to assume my overlay of the preliminary geophys results is exactly right, which it may not be - wish there were OS grid refs of the pits available right now)."

But then the East pit has the wrong date?

http://mikepitts.wordpress.com/2011/11/29/view-from-the-heelstone/#comment-956

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jonmorris

Re: More accurate data (Re: Stonehenge Hidden Landscape Project - Cursus/HeelStone solstitial alignments) Simon - 22:43 01/12/11
We're operating in an information vacuum - attempting to deduce alignments from a couple of images with no proper georeference data. It's fun, and interesting, but ultimately not very much use.

The image from the 2010 preliminary report at least had OS grid ticks along the margins, the ones overlaid on the Google Earth backdrop I don't trust as much (because I have little confidence in Google Earth's accuracy in the orthorectification of aerial photos).

I do not understand why the project doesn't make available the OS coords of the supposed pits. I look forward to an actual paper being published that might shed some light on this.

Then there's the horizon altitude to consider in each of those directions which could easily affect the angles as pointed out in your comment on Mike's site (sunrise and sunset are not necessarily symmetric about the meridian unless horizon altitude is exactly the same in each direction), the possible viewing locations (at the Heelstone? SE/SW of the Heelstone on each alignment?) and even whether the builders intended a precise or simply a symbolic alignment (the "near enough is good enough" approach).

Finally, I simply don't buy the processional route midpoint theory at all.
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simon

Re: More accurate data (Re: Stonehenge Hidden Landscape Project - Cursus/HeelStone solstitial alignments) Jon Morris - 07:48 02/12/11
I pretty much agree with everything you've said

Not sure about using google for checking either but the same result comes out from other mapping systems and those results also appear to correlate with the results of the methodology that you used.

I don't buy the processional theory either.

Rgds

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jonmorris