Sinking in the earth’s (muddy) magnetic field…

I am wearing $28,000 of sensitive electrical equipment and sinking deeper into the rice paddy with every step. By this point, its pretty apparent that I am going to need some help.

I am carrying a device called a gradiometer. It measures anomalies in the earths magnetic field. Our team is using it to look for Mongol shipwrecks buried somewhere (we hope) beneath meters of mud and rice. The gradiometer’s cesium sensors pick up fluctuations caused  by buried iron – perhaps corroding armor or fasteners in the hull of an ancient ship – and heated material, such as brick, burned rock or ceramics

Watching the livestock while on a survey break - © 2011 Veronica Morriss

The device is really expensive, meaning: don’t get it wet. To make things worse, there are a number of people watching, including a pack of laughing Vietnamese children. Vietnamese children always seem to be laughing or smiling, even when they are working hard. At this point, they are running circles around me, almost if they could run on the top of the water itself.

Boys running through the inundated rice paddy - © 2011 Veronica Morriss

The rice field is inundated with runoff from the irrigation ditches. Some places you can maintain your footing. This was not one of them. For the third or fourth time today, a slurry of dirty water was threatening to come over the top of my rubber boots. Normally, I am not bothered by a little mud – but this is rural Vietnam, and the water is teeming with parasites that will knock you flat if you get them in your system.

I sigh. “Veronica – I am going to need some help.” My partner has been standing back so that she doesn’t interfere with the sensor readings. She returns the sigh with the air of one much put upon, and makes her way over. I shouldn’t be stuck… again. In my defense it is hard to judge the consistency of the muck before you put your foot down. Plus, the equipment adds some 45 lbs.

Veronica reaches down, grabs my rubber boot, and pulls my foot out of the mud with a squelch. As she pulls, she sinks in a little further, so its my turn to pull her foot out. Then my foot, then her foot and my foot again… in this way we crab our way back to firmer sludge.

We have been surveying this field for hours. The process is arduous and repetitive, but I relish being in the field, doing archaeology. A magnetic sensing survey is like mowing the lawn. We walk back and forth across the paddies, each transect a few meters apart. As we move, a GPS receiver on my heavy pack maps my position. To make sure we walk in a (somewhat) straight line, we follow cues from a head-up-device called a swather. It’s mounted on an arm that extends over my left shoulder, and reminds me of the targeting apparatus Luke Skywalker used to take pot shots at Death Star.

Following directions from the swather - © 2011 Veronica Morriss

Its been a long morning. I am exhausted and my shoulders hurt; moreover, getting stuck is evidence that I am making poor choices about my survey path. Its time for me to switch out and let Veronica take over. This is an unnecessarily complicated process.

The gradiometer is cumbersome. I am carrying a two meter boom with a pair of cesium sensors mounted on one end and a heavy counterweight on the other. A tangle of wires connects the sensors to a computer hanging around my neck. I am wearing a non-magnetic frame pack with a Trimble GPS antennae, transceiver and swather, along with a pair of ridiculously heavy batteries. Without the sensor pole, the pack weighs some 35 lbs – and I am sure it was designed by an engineer who really disliked archaeologists. The crew calls it the “The Rack of Pain.”

Transferring the entire rig without setting it down (in the mud) is a tricky dance, especially for only two people. I let the counterweighted end of the boom rest on a dike and hand the computer to Veronica for safe keeping. She steps behind me and lifts the pack while I unclip myself and step out. I balance the boom, take the computer back, grab hold of the frame and rest it on my knee while she flips around front side and into the harness. She clips back in, takes back the computer, slips the boom into position and powers back on.

Veronica moves out of the mud onto firm ground - © 2011 Douglas Inglis

While the sensors are on, they sing. The pitch goes up when the gradiometer senses a strong magnetic field, and down when the field changes. When you find a really strong magnetic signature, the device sounds like a robot in estrus. It terrifies the heck out of most of the Vietnamese children. I convinced some braver individuals to wave their sickles at the device (yes – the kids run around with sharpened sickles). The tone changes when the blade is close, and drops when they take it away.

While we are in the field, we can “feel” out an anomaly by passing the sensor rod back and forth over them. The pitch rises and falls, and we can get a sense of the anomaly’s shape and strength. We laugh about it – but when all is said and done, mag survey is high tech dowsing. We are led by spirits in the earth.

– Doug

Spirits - © 2011 Douglas Inglis


Special thanks to the entire Bach Dang crew: Randy Sasaki, Jun Kimura, Dr. Mark Staniforth, Dr. Le Lien Thi, Britt Burton, JB Pelletier, John Pollack, Dave Ross and especially Minh, without whom we would never have been able to find our way around!

Tags: , , , , , , , ,

Categories: Adventure, Archaeology, Remote Sensing, Travel, Vietnam

Author:Doug Inglis:

I study the archaeology of seaborne exploration and contact. I am passionate about public history and outreach, and write about nautical archaeology at

86 Comments on “Sinking in the earth’s (muddy) magnetic field…”

  1. February 19, 2012 at 3:08 pm #

    “We laugh about it – but when all is said and done, mag survey is high tech dowsing. We are led by spirits in the earth.”

    That’s the kind of sweet line that’s going to run circles in my brain for the better part of the afternoon… absolutely fascinating stuff, to boot.

    • February 19, 2012 at 6:45 pm #

      Thanks! We know people who have a talent for dowsing – one is even an archaeologist. Its beyond me. When I worked in Rocky Mountain National Park our PI consulted with Ute elders who had insight into the sacred spaces of the mountains – they helped reveal aspects of the landscape and archaeological sites that we had missed, even after surveying the area numerous times.

      • February 20, 2012 at 2:48 pm #

        Again, that’s absolutely fascinating stuff… I mean, I think the layperson’s understanding of how truly remarkable this kind of field work is tapers off somewhere around “Jurassic Park…”

        i.e. “You shoot a magic magnetic bullet into the ground, and it just shows you EVERYTHING that’s buried in a file-mile radius… then you call it a day, and crack open a Pabst!”

    • February 24, 2012 at 1:18 pm #

      I’m with Mel. That really is a great last line.

      • February 24, 2012 at 4:49 pm #

        To be fair, Mel, my understanding of these things tapers off more around Walking With Dinosaurs than Jurassic Park. Give me a little credit.

        Anyway, I always liked archaeology. I like palaeontology better, but still.

      • February 24, 2012 at 7:27 pm #

        agree, agree

    • March 11, 2012 at 7:46 pm #

      That’s awesome! I wish you good luck!

  2. February 24, 2012 at 1:01 pm #

    You look like the Ghostbusters will your equipment.

    • February 24, 2012 at 3:27 pm #

      Thanks! The two cesium magnetometers on the boom actually kind of work like the PKE meter from Ghostbusters. Our device actully sound similar – we just look for magnetic fields, instead of Psycho-Kinetic Energy.

  3. February 24, 2012 at 1:34 pm #

    That is some fancy backpack!

    • February 24, 2012 at 3:31 pm #

      I wish it was a fancy as it looks from a distance – it could use some strategically placed padding!

      • February 24, 2012 at 5:04 pm #


    • Patrice Ferguson
      February 26, 2012 at 2:19 am #

      Now that you know what you need in the way of machines and scanners perhaps you could get apple to down size that into a tricorder? I know very star treky but even so.

      Or at least get it all to fit in a back pack minus the wand that would do instead of a boom? Unless of course it has to be sticking that far out in front of you. It is pretty incredible work your doing and making your own equipment along the way.
      Good luck with it.

      45 lbs more then you weigh in a rice patty it is amazing you were not up to your hips in mud.

  4. February 24, 2012 at 2:26 pm #

    If a swather “reminds me of the targeting apparatus Luke Skywalker used to take pot shots at Death Star”, then that makes it about the coolest piece of equipment that you have.

    I just feel that needs to be said. 😉

    • February 24, 2012 at 3:29 pm #

      Agreed! However I have about as much luck following the swather as Luke did using the targeting device. If you try to follow it exactly, your lines will wiggle. Instincts are more accurate – the swather just helps remind you to stay on course!

  5. February 24, 2012 at 3:12 pm #

    I’m an engineer and this is the first time I’m reading a post on Freshly Pressed on anything remotely technical. Sounds really exciting. When you do discover a Mongol warship, what happens next?

    • February 24, 2012 at 3:49 pm #

      Thanks so much for your comment – making science accessible is really important to us.

      As far as what we do when we find a wreck – its complicated. We work with local people to do what is best for the site. Ideally we excavate the wreck and carefully record it. We map, draw and photograph every artifact. We also map the ship as accurately as we can. Sometimes this means using a tape measure, sometime this means scanning it with lasers. We record every detail – every cut, nail hole and mark – because we can reconstruct how the ship was put together piece by piece. It lets us get into the mind of the shipwright.

      When waterlogged wood is exposed to air, it will warp and distort as it dries. Organisms may attack, and damage is likely. We have to keep the hull wet at all times – or the ship will loose its shape. To preserve the site for posterity we may rebury it.

      In rare circumstances, an entire ship is raised and conserved. We replace the water in the wood with wax. It can take decades, and millions of dollars. The Conservation Research Labratory at Texas A&M did this for the Belle, one of the ships of French explorer Robert Cavelier, Sieur (Lord) de La Salle, lost in 1686. You can see pictures here:

  6. Tony
    February 24, 2012 at 5:30 pm #

    Very interesting work, Doug! Thanks for sharing it with us!

    • February 25, 2012 at 2:28 pm #

      Thanks for your interest! I believe that active public outreach is an obligation that comes with the privilege of excavation. Each excavation is a unique piece in time, its important to us to make as many people as possible part of the moment.

  7. February 24, 2012 at 5:45 pm #

    Absolutely fascinating. I love your blog and really appreciate you telling us about the experience. I certainly will be a “regular customer” to your web site.

    Take care.

  8. February 24, 2012 at 7:28 pm #

    fascinating article – about an (I suspect) not very fascinating day

    • February 24, 2012 at 7:43 pm #

      Ouch! The truth hurts! Honestly – we really loved being out there in the sun and surrounded by beautiful people. Plus: Veronica reminds me, it beats the heck out of coring.

      • February 24, 2012 at 7:50 pm #

        wasn’t implying that you shouldn’t like your day – If I described my average work day it would sound like the definition of tedium!

        But you do have a great turn of phrase (and pics) which make clambering around a muddy field in the ‘rack of pain’ sound quite fascinating 🙂

  9. February 24, 2012 at 8:25 pm #

    Great photographs!

  10. February 24, 2012 at 8:48 pm #

    Like the metal detectors old guys use in playgrounds looking for coins kids drop.

  11. February 24, 2012 at 9:53 pm #

    Great story & what a great job! Reminds me of when I saw the Dover Boat in England. hard to pinpoint probably, but what period are we talking about & where exactly in Vietnam are you looking?

    • March 4, 2012 at 9:31 pm #

      We were on the Bach Dang River in Vietnam. Enter this location into Google maps: Nam Hòa, Yên Hưng District, Quảng Ninh Province, Vietnam

      We are looking for 13th century Chinese vessels – the Battle of the Bach Dang occurred in 1288. At that time, Vietnam was flip flopping between independence and being a vassal of China. There is a short description of the project here: and more by project director Randal Sasaki at the INA website here:

      PS – It must have really been amazing to see the Dover Boat – I have read much about it, and am jealous of your chance to visit!

  12. February 25, 2012 at 12:34 am #

    Reblogged this on Atomic Yeti.

  13. February 25, 2012 at 12:59 am #

    “We laugh about it – but when all is said and done, mag survey is high tech dowsing. We are led by spirits in the earth.”

    Your whole article was interesting, and I am sure it gets more interesting when you find what you are looking for.

    But I have to tell you the above quote of your last line grabbed me! I love dowsing. My father was a developer and he trusted his dowsing skills more than what a geologist could give him. He always said it was more accurate for him to dig for a well after dowsing, than it was to pay for a geologist’s report. He could also find deeper water too. When I got married I met my now ex’s uncle who was a world renowned dowser. He could look at a map and tell you what exactly was in what part of the land. If you had paid the geologist and had gotten bad tasting water, he could from a map tell what was in the water, and could move cleaner water to your well. He also used dowsing for healing purposes, and taught all over the world. As far as the commenter above commenting on Ghostbuster’s, He was often hired to travel all over the world and remove ghosts from castles and old homes of Europe. The two are very closely related.

    So as a child I use to go out with my dad and walk the land with either two metal rods or a willow twig. Now I work with a pendulum, and I have been wanting to try working on maps. My talent lies more in clearing negativity attached to something than moving water. Truthfully, I have to tell you it is all the same. I use my pendulum just like we used the rods when I was a child. We are working with the same magnetic fields you are working with except I spent 12 dollars on my pendulum, and you spent a lot more on your pain rack.

    Oh my gosh! I am so sorry, I got totally carried away on this comment. But your last line stated exactly what I have known for years about dowsing. It is all about the magnetic fields.

    Peace and Harmony,

    • Veronica Morriss
      February 26, 2012 at 5:39 pm #

      Thanks for your comment! We actually had a person on the project who is an experienced dowser, though he did not use this technique (to our knowledge). I have always been fascinated with dowsing. My grandfather is very good at it just like your father seems to be. He uses a pendulum, too. He taught me a couple of years back, though I have not yet used it for archaeology, though my grandfather insists that I should 😉 Either way, I always keep my pendulum close by. I would love to learn more about it!

      • February 26, 2012 at 10:53 pm #

        Walter Woods wrote some good information on it and you can download his stuff from the internet. He was renowned in the field. He was my ex’s uncle. We had some very interesting conversations over dinner at different restaurants. Yes I do believe that you could really learn to use your dowsing for archaeology. With practice you could pin point places to start looking for boats in the rice fields! I can not imagine walking out through those muddy fields! I live on a ranch in California that grows rice. As a matter of fact my back window is 50 feet maybe from the a rice patty, so I know about that mud. It must be clay to begin with because it has to hold water for the rice to grow. The guys occasionally get their trucks stuck in the mud out here and have to be pulled out. We only have to deal with the mosquitoes, but you are talking there about parasites too. Well mosquitoes, rats galore, and frogs in my house… I love the lizard family that lives on my front porch though.

        Archaeology and Archaeologists have always fascinated me. I am not one for the outdoors, so it is hard to imagine what you all go through to find what you are looking for. I would definitely practice with your pendulum and in time it should be able to guide you right to what you are looking for. It will point right to what ever you ask it to find either out in the field or on a plot map of the area. Thanks for replying… Sj

  14. February 25, 2012 at 2:45 am #

    First thought– “How very intriguing”, second– “Star Wars reference, how rad” –By this point I was planning to follow and then I read the last line… I really do want to follow you around the globe and beneath the waves.

  15. SandySays1
    February 25, 2012 at 8:17 am #

    Wow, that’s quite a device. My human loves “Archy” stuff, as he calls it, and helps at the Randell Research Center on the Gulf of Mexico in Florida. It’s a site inhabited by Calusa Indians for most of that period. I showed him your post. He wonders what would be discovered walking those grounds toting that pack around. The archaeologists there have already discovered that the Gulf’s sea level has varied by six feet over the last 2000 years. That’s 4 feet higher and 2 feet lower. It’s amazing what can be learned from the past.

    • February 25, 2012 at 3:04 pm #

      Tell your human that mag survey is really useful for finding ephemeral remains, such as ancient hearths, broken pottery and graves. I am sure it would be very effective! Thanks so much for your comment. We love it.

  16. February 25, 2012 at 10:03 am #

    Some high tech gear there…….great pictures


  17. February 25, 2012 at 11:05 am #

    This is so cool! High Tech Rocks!

  18. February 25, 2012 at 11:26 am #

    You have possibly one of the coolest jobs ever. You can genuinely associate yourself with Indiana Jones type people when talking about your career. I’m jealous.

    • February 25, 2012 at 2:49 pm #

      Thanks! We love our job. At times it is tedious, at times it is thrilling; thankfully, unlike Indiana Jones we have never had to survive a nuclear explosion by hiding in a refrigerator.

  19. February 25, 2012 at 12:44 pm #

    I just wanted to say, you are obviously very committed to your (tedious) work. My knowledge of archeology stops at Jurassic park – and David Schwimmer’s character on “Friends” was a paleontologist. Of course now I am going to have to look up what the difference is (so sad). But since I do know about TV here is a humorous fan video you might enjoy from the show “StarGate SG-1” Its called “Daniel Jackson – He’s an archeologist.”

    Good Dowsing

    • February 25, 2012 at 3:08 pm #

      SG-1 was a good show, but I really love the movie! (Guilty pleasure) Plus, I thought James Spader did a great job as Daniel Jackson.

      • February 25, 2012 at 3:26 pm #

        So the rest of your job is just like the video?

  20. February 25, 2012 at 1:40 pm #

    Loved your article! Very interesting….

    $28,000 worth of equipment and The Center for Disease Control want you and Veronica to have your very own pair of waders. Check out:

    Only $99! Also a great way to sweat out toxins in the tropics….

    • February 25, 2012 at 2:39 pm #

      LOL. I am glad the CDC is thinking of us! We will heed the advice when (hopefully) we go back in 2013!

    • February 25, 2012 at 2:46 pm #

      Awe, that’s a let down. I thought the CDC was paying. Doug & Veronica don’t already HAVE these BECAUSE OF $28,000 worth of equipment. 🙂

      • Veronica Morriss
        February 26, 2012 at 5:46 pm #

        Amen to that!

      • February 27, 2012 at 2:07 pm #

        Why are researchers underpaid? So wrong! I guess you take your paycheck in being able to stomp around in the mud. 🙂

        As for the CDC, a friend of mine was a chemistry teacher for the Peace Corps in Gabon (West Africa). He came home to the US with three different kinds of tropical parasites, and the CDC wasn’t quite sure how to treat him because the medicines for the different parasites interacted with each other. My friend’s body became a sort of chemical la-bor-a-tory (yuk, yuk, if you know what I mean). It seems the scientists, at least some, like to experiment on each other.

  21. February 25, 2012 at 10:26 pm #

    I bet you would find some interesting stuff at this place with your kit:
    Built in 1480, genuine celtic castle, treasure found in early 1800’s. Done a couple of film shoots here but would love to dig! By the way, found a 4,000 year old oak road near here four moths ago .. amazing! Visit the place if you make it to Ireland you will be astonished.

    • March 4, 2012 at 9:37 pm #

      I have only briefly been to Ireland, but loved it. They have the most amazing archaeological collection at the National Museum of Ireland. I could have spent days on end in their collection. The castle looks incredible. I am sure there are layers upon layers of history buried around the castle grounds.

  22. February 25, 2012 at 11:11 pm #

    Ahaha Ghostbusters that is the name!

  23. Aini
    February 26, 2012 at 5:28 am #

    This is a really cool post! It was an eye-opener, showed that archaeology’s not just digging artifacts from the earth, but also integrates manual methods with satellite technology. Really, really cool.

    I’m not an archaeologist myself, but I love all things archaeology – especially ancient Egpyt. Also, I occasionally dive so I enjoyed reading your other posts on underwater archaeology.

    Congrats – you’ve got yourself a new follower! 🙂


  24. February 26, 2012 at 8:31 am #

    Very cool! Very ghost-bustery! Happy huntiing & thanks for sharing….also loved the pics!

  25. February 26, 2012 at 9:27 am #

    Just amazing

  26. February 26, 2012 at 9:36 am #

    Archaeology on freshly pressed – fantastic!

  27. February 26, 2012 at 10:02 am #

    Definitely one for those who think science isn’t exciting… it is in the field!!! =)

    • March 4, 2012 at 9:48 pm #

      We both live for fieldwork – which I think is true for most archaeologists. I am constantly surprised/reminded, however, by how much fun there is in chasing clues through the archives, or in the lab. Thanks for the compliment!

      • March 5, 2012 at 8:27 pm #

        Totally agree, not an archaeologist, but studying ecology, and bringing theory into practice is the best, seeing that it really works and that it does make sense =)

  28. February 26, 2012 at 10:24 am #

    Incredible post! i applaud your efforts to impact your world in a positive way!

    • March 4, 2012 at 9:51 pm #

      Thanks so much! The world has such an incredible depth of history and cultural heritage. It should be accessible to people everywhere!

  29. February 26, 2012 at 11:19 am #

    Wow, great photographs!

  30. February 27, 2012 at 8:45 am #

    I had a little chuckle reading this. I’ve been invloved with wetland studies and know full well that mud is a very sticky situation. Once I sunk in hip deep and my fellow researchers had to improvise a bridge with pieces of plywood to rescue me! What was even worse, I had to head to a parent teacher conference immediately afterwards! Fortunately our equipment was only plastic baggies, rulers, and pvc transects. Keep up the good work!

    • March 4, 2012 at 9:55 pm #

      Wow! What a hilarious experience (at least after the fact). I hope you did not track globs of mud across the floor. I am glad you had some bright folks to help rescue you – it sounds like a great opportunity for field engineering. Mud up to my hips would have put me in a bit of a panic! Great story, and thanks for the comment!

  31. February 27, 2012 at 9:46 am #

    Awesome post, I love your efforts!

  32. February 27, 2012 at 12:30 pm #

    “like a robot in estrus” haha

    did you get any good readings in the end?

    • March 4, 2012 at 10:12 pm #

      We are still post processing some of the data, and I am limited on what I can announce before publication. We located a number of anomalies that looked like graves – so were we reticent to test them out (ie, excavate). We had a few other interesting hits it the inundated area, but because of field flooding, we couldn’t effectively test them either. We hope to head back in 2013 and follow up on the project. Getting excavation and survey permits takes time!

  33. February 27, 2012 at 1:49 pm #

    Really fascinating article I look forward to reading much more.

    Good to read in depth and well written articles on archeology and your love for the field is evident in your enthusiastic writing style

    Great stuff and thanks again.

    • March 4, 2012 at 10:07 pm #

      Thank you very much for the compliments! We both love being able to share our experiences and work with a wider audience. Too many archaeological project vanish into the nether-regions of academia. We will try our best to keep good content coming!

  34. February 27, 2012 at 10:53 pm #

    Reblogged this on .

    • March 4, 2012 at 9:57 pm #

      Thank you for reblogging us!

      • March 7, 2012 at 7:17 am #

        You are very welcome for the reblog. I have always found treasure hunting to be fascinating. My experiences however were limited to using a simple metal detector to hunt civil war artifacts in my hometown.

  35. March 4, 2012 at 9:56 pm #

    Thank you all for your comments and likes, we are overwhelmed – and appreciate every one!

  36. March 15, 2012 at 11:59 am #

    Very nice report, though I do have to say that it looks like an awful lot of equipment when you compare it to the stuff they have developed at Sheffield University – and that gets used on the UK TV programme called “Time Team” for the ground survey work.

    I won’t say they don’t sink up their ankles too – because they sometimes do, even when they are not in a paddy field! Nicereport.


  1. Sinking in the earth’s (muddy) magnetic field… | Electrician Dallas - March 6, 2012

    […] Reblogged from Diving | Archaeology: […]

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