Tip o’ the Week # 92 - On Compasses

In the past, I have railed against the inaccuracy/accuracy issue with science and the Earth Mysteries (see "Tip" 85 - "How Accurate is Accurate Enough?".  Yet I find that the pendulum has swung the other way, and now I am arguing that one of the basic tools Earth Mystery enthusiasts have been using, the compass, is nowhere near accurate enough.  This "Tip" is a bit longer than usual because in addition to fascinating info on the use of compasses, I have several other bits of news to tell you about including that I am planning to put these "Tips" on hold for a while. So I apologize in advance about its unusual length, but trust it is worth your attention.

I am having more and more questions about the use of compasses in Earth Mystery/ Archaeoastronomy work that I have done for the last thirty-five years.  I have long been using a Suunto Tandem that I thought accurately measured both azimuth and angle of elevation to the horizon, but when I was recently up in Anglesea with my Geomancy Group, I had a rude awakening.  We were at the house we were staying when I discovered that my readings did not agree with the compasses of others in the group.  I laid it down to being in a magnetic anomaly; however, I found these dissimilarity of compass magnetic azimuth readings was also the case at various chambers and dolmens on that island!

So when I came home to Glastonbury, I was working with Andrew Cox from Bristol (you may know him through the BSD?) and only a few of the compasses tested agreed with each other, and they were clustered in two groups eleven degrees apart!!! 

My diningroom table/major azis

We used the longer side of our dining room table as a long barrow to shoot the magnetic azimuth of the major axis of the table/longbarrow (only we aligned with the routed (grooved) edge of the table for greater accuracy). 

In addition to my Suunto Tandem pictured above, we tested a number of different compasses - a regular Sylva, a smaller Suunto, and six compass software apps I have on my iPhone 4.  We aligned each in the same place on the longer edge of the table, and their Magnetic readings differed by as much as thirteen degrees! (We did not correct for magnetic deviation.  Here in Glastonbury today it is
2° 31' W changing by 0° 9' E/year. )

Suunto Tandem
This Suunto Tandem is the most potentially
accurate hanad held compass I know of. 
It also has a clinometer to measure the
angle of elevation to the horizon.

Suunto KB Sylva
   This Suunto KB had the highest azimuth reading         This is an orienteering compass
no name i4 Digital Compass
A military looking one with no manufacturer!        First of the iPhone Apps
GPS (Wm.mcrae) compass version 1.2
      iPhone GPS by William McRae
    iPhone Compass version 1.2
Handy GPS
                 Handy GPS

Theodolite Pro

Initially, I did not picture one more iPhone App
(perhaps the most useful App),
Theodolite Pro (Hunter Research and Technology.
It showed an azimuth of 356º.
Surprisingly, it had the highest azimuth bay far, but was
only 6º Westof the Handy GPS above.

Byron Dix, who wrote "Manitou" about the astronomical alignments of the underground stone chambers in New England, was my mentor for the  study of archaeoastronomy in the nineteen-seventies.  He basically told me that if you're going to use a compass to shoot astronomical alignments, "you should strip nekkid!" (Read: Clothing many times will pull the compass needle.)

While we were not "nekkid" when comparing our compasses on my dining room table, if our clothing was pulling the needle off, all of the compasses should have shown the same deviation.  But that was not the case.  They really varied from each other quite a bit!  This ain't close enough even for government work!!  (That's supposed to be a joke  ;  )

So my questions are these:  Who/what can we trust here?  Do I really have to get a transit like Alexander Thom had to be able to trust the azimuth I'm shooting?

Dear reader, if you have done this work, what tool(s) do you use?  Have you noticed that different compasses in exactly the same place give different azmuthal readings?

Why haven't I noticed this before?


I wrote my friend archaeoastronomer and dowser Robin Heath (I recommend that you check out http://www.skyscript.co.uk/moonheath.html) reporting what I had run in to.

Robin replied with helpful clarity not only confirming the reality of what I had found, but also he offered some solutions for greater accuracy:

"The reason you may not have noticed this variance before is that the earth's magnetic field has been progressively weakening since you were born. [There is probably no connection between the two events!] 'Stiction' within the crude bearings of cheap compasses mean that they progressively stick near to where the needle would like to go, but cannot because its gets stuck en route. Every make of compass has a different stiction point, hence everyone fights because they all get a different angle.  Earth mysteries people have been known to fight over much less important matters than this fundamental error!

"I do not like compasses for my work, because:

" a) they are pretty useless for archaeoastronomy apart from mildly suggesting where the sun and moon may rise and set to perhaps five degrees, which then means that if you have 'found' an interesting possible alignment, you then have to analyse it further with a theodolite or 'other methods' and you’ll also need the angle of elevation of the horizon or foresight. (More on this later).

" b) over igneous or 'faulted' geology they often are 'out' by as much as 20 degrees. Some locations in the Preselis actually cause (within 6 feet or so) the needle to reverse itself and then resume its original, still inaccurate, position. The cause is ferruginous rocks underfoot whose magnetic field was frozen to the opposite polarity in the very distant past. Isn’t ferruginous a great word?

" c) they are usually far too small to even read their inaccurate readings accurately!

"So, yes, I suppose if you want to throw away your 'white stick' of azimuth blindness, you will need something better. I use a theodolite (£300+) which is heavy, awkward and which takes some time to set up. Once set up it can get the azimuth to better than 20 seconds of arc, even better is you shoot the sun or moon's position and time it, later comparing the result and correcting it against an almanac or ephemeris (all on the web these days), which sets the azimuth to better than a minute of one degree.   A theodolite also gives you the vitally important elevation angle of an horizon or celestial body to the same accuracy. With a theodolite one can survey a stone circle in less than two hours, using a tape (£15), and about an hour using a laser rangefinder (£700). A horizon profile can be undertaken in under a couple of hours. Then it's all done and dusted and you don't have to keep going back there again and again to check it all out more accurately.

"Another and cheaper solution to determine azimuth accurately enough for most 'earth mysteries' use is to use a GPS. Define a central point. [technical top tip: check that you have set the GPS to OSGB36 if you want the coordinates to tally with those on the OS map].  Walk the GPS such that the longitude ain't changing and you must then be walking dead north or dead south. The same technique with latitude must yield an east-west line. Staking these two axes with ropes or string then has defined the cardinal points. A large protractor like wot teachers used to use with blackboards at school ( 2' diameter) can then be used to enable the identification of a given  azimuth. I have made my own protractor and have used this method many times at sites like Avebury and Stonehenge when with a group and too little time to set up a theodolite, and it easily gives results to better than one degree if you walk the rope and stake 100 yards in each cardinal direction from the central point.

"Finally, on eBay one can sometimes find for sale simple school theodolites made by Philip Harris, Birmingham, which have a no magnifying lens in the ‘telescope’ tube connected to a spirit level, but has crosswires and two protractors which are mounted for azimuth and elevation. They fetch about £40 and I have two I have used for my archaeoastronomy courses. They are good to about a degree, i.e. just about ample for basic work.

"You can find out much more at www.skyandlandscape.com (two free download PDFs about all of this, and theodolites too - in the Learning tools and free programs section).  There’s a whole lot more within my recent book Bluestone Magic, available via the website. Fabulous value!

"All the above are my personal opinions and suggestions based on 25 years of surveying sites all over the place. It has been my experience that the earth mysteries movement needs to get savvy with all of this stuff if it is to avoid the awful errors it has sometimes announced as dramatic discoveries in the past. For example, the grid lines on OS maps are not aligned to the cardinal points, yet one hapless ley hunter (whom I won’t name but whom we all know and love!) based a whole theory about ley lines assuming they were so aligned. 

"I hope this helps.



Robin's words are cause for some deep thinking.  I certainly agree with the reality that our prehistoric foremothers and fathers aligned their sacred sites astronomically, but if we who approach these sites from an archaeoastronomical point of view, to have any credibility with other groups that are also interested in these sites, it is clear that we gotta use other tools than compasses.

----------------- Other News -------------------

This will be my last Tip o' the Week for a while.  As I wrote at the end of last year, I intend to write an ebook on various aspects of this material, and I am finding that writing these Tips is taking up too much of my writing time.  I suspect that I might be occasionally send you one of my Archived Tips that I feel might bear repeating, but I'm going to concentrate on my eBook for a while.  Please continue to write if you have any thoughts or questions.


You might want to visit our "Tip o' the Week" Archives at: <http://www.geomancy.org/listmessenger/public/archive.php>.  There are now 90 Tips you can troll through.


You also might enjoy checking out Karin's Blog at <http://karinschluter.nl/blog/>.


This summer, for those of you who live in or near the UK, I am teaching a course for the British Society of Dowsers on the Oxfordshire/ Warwickshire border at the Rollright Stones.


BSD Earth Energies 5
Advanced Earth Energies Dowsing:
Working with Power Centres and applying Geomantic Design

with Sig Lonegren
Sat 9 and Sun 10 July 2011

Venue: Long Compton Village Hall, Shipston on Stour, Warks (near Rollrights stone circle)
Cost: £149 including tea/coffee & lunches.?
Further Information & Booking: Call 01684 576969 ?or email info@britishdowsers.org

I'd like to meet you there!

Sig's sig
Sig Lonegren
MAG Webmaster
SunnyBank, 9 Bove Town
Glastonbury, Somerset
England  BA6 8JE
+44 (0)1458 835 818