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Free archaeology - PhaseSI - 10th September 2013
kevin wooldridge Wrote:Geofizz is probably the one area of archaeology that has the fewest cross-overs with other disciplines....there aint much else you can do with the equipment other than archaeology and using it to keep doors open.....
Just came across the end of this thread and was compelled to join in! I'm assuming that either people aren't too up to date with geophysics or else have used some very mediocre contractors ...
Regarding Kevin's comment above. Archaeological geophysics is just one of many applications of near-surface geophysics and is not even the biggest. I can't think of any other archaeology related discipline that has as many non-archaeology applications. Dino lists a few and rightly points out that looking for buried services is one of the main applications (with GPR being standard in this) and is in fact a much bigger sector that archaeological geophysics. Other applications include looking for underground storage tanks, buried foundations, old basements, mineshafts, mine adits and deeper workings, solution features, mapping near-surface geology and bedrock profiling, unexploded bomb or ordnance detection, assessing the condition of roads, soil mapping, locating rebars, bridge inspections, mapping rail ballast variations to name just fourteen or so (I’m not including oil, gas or mineral exploration here ...). There's probably a few more listed on our website.
However, Dino's comment of '...but I agree, geofizz can't characterise the archaeology of a site, however good it is, merely provides some hints'. I'd say that in many (but not all) cases ii should provide more than a few hints. I.e. this site contains multi-phase Romano British features but to get specific dating and confirm the relationship between features you need to excavate here and here. A bit more than a 'hint' surely. Geophysics can be an evaluation tool in its own right but is obviously best used to target trenching. But for an evaluation (presumably trenching?) to be able to undercut any mag survey and provide as much information across the entire site
(couldn't find a 'falling off chair' laughing emoticon).Unitof1. Would you price up an excavation on a mag survey? In some circumstances yes. To cost for trial trenching then yes. For open area excavations -yes if the geophysics has been followed up by targeted trenching (although I guess this may depend on who devised the trenching strategy). In all cases, assuming a DBA had been done. To cost for excavation without using / considering geophysics smacks of amateurism, bad practice and a predisposition to not want to find archaeology and / or waste your clients money.
Dino - it's usually c**p at finding stuff like hundreds of bodies or Neolithic pits for a start'. Has been used very successfully to find the former (though is very site dependent) and with higher resolution surveys now commercially viable (0.5 m spacings with readings taken at 10 cm to 20 cm intervals) then discrete features are now more likely to be detected.
PS. I wouldn't be characterising prehistoric landscapes with archaeology but I would be giving some pretty big 'hints'.
Free archaeology - Dinosaur - 10th September 2013
You'd be amazed how many times we've dug stuff on the assumption from geophysics that it was one thing, but then found it was something completely different. And very, very often trenching has to be undertaken in order to characterise whatever the geofizz has picked up - it's amazing how many ways land- and French-drains can reveal themselves via magnetometer for instance, whilst, in the case of a job I did earlier this year, pretending to be elements of a RB enclosure system...got 'em figured now, but it took 57 50mx2m trenches to resolve things and understand the survey data...
Higher resolution magnetometry is, indeed, the way to go, and I'm sure one day commercial archaeology will grit its teeth and give it a go, but in the meantime skellies and Neolithic pits will have to be found by skill and Mark 1 eyeball
You weren't the only one needing a hand back into your chair after reading Unit's comment
Free archaeology - PhaseSI - 10th September 2013
Dinosaur Wrote:You'd be amazed how many times we've dug stuff on the assumption from geophysics that it was one thing, but then found it was something completely different. And very, very often trenching has to be undertaken in order to characterise whatever the geofizz has picked up - it's amazing how many ways land- and French-drains can reveal themselves via magnetometer for instance, whilst, in the case of a job I did earlier this year, pretending to be elements of a RB enclosure system...got 'em figured now, but it took 57 50mx2m trenches to resolve things and understand the survey data...I wouldn't be too amazed. There's a lot of 'variability' in geophysical surveys depending in the experience, qualifications and skill of the geophysicist.
Dinosaur Wrote:Higher resolution magnetometry is, indeed, the way to go, and I'm sure one day commercial archaeology will grit its teeth and give it a go, but in the meantime skellies and Neolithic pits will have to be found by skill and Mark 1 eyeball
You weren't the only one needing a hand back into your chair after reading Unit's comment
We have gritted our teeth and are regularly using a 6 sensor system with the sensors spaced 0.5 m apart and readings collected every 0.1 m to 0.2 m. Very impressive data if I do say so myself and no more expensive than a traditional hand-held survey. For the sake of fairness I should add that Archaeophysica also use a high resolution system and have been for some time.
Free archaeology - Dinosaur - 10th September 2013
Actually on a lot of the subsoils around here the S&M1E approach may never be replaced by geophys, but keep it up anyway - and please stop topping-and-tailing the mag data, assuming you're also guilty of this crime, just hand the lot over, we've had several potential projects that have been killed-off by geophysicists refusing to provide raw data
Free archaeology - PhaseSI - 10th September 2013
Dinosaur Wrote:Actually on a lot of the subsoils around here the S&M1E approach may never be replaced by geophys, but keep it up anyway - and please stop topping-and-tailing the mag data, assuming you're also guilty of this crime, just hand the lot over, we've had several potential projects that have been killed-off by geophysicists refusing to provide raw data
Geophysics should only very rarely replace excavation but even on 'tricky' soils a well done geophysical survey can provide useful information.
I think the only reason not to hand over raw data is if you're tying to hide bad data collection that has been processed out so I'm guessing it may not have been geophysicists who didn't hand over the raw data, but someone who wasn't trained properly using geophysical equipment. A handy hint - look for data that has been clipped to standard deviations and not absolute values and ask what the data range is. If its too large ask why the range is so high. Occasionally its down to site conditions but most of the time its bad data.
Free archaeology - kevin wooldridge - 10th September 2013
PhaseSI Wrote:Regarding Kevin's comment above. Archaeological geophysics is just one of many applications of near-surface geophysics and is not even the biggest. .... Other applications include looking for underground storage tanks, buried foundations, old basements, mineshafts, mine adits and deeper workings, solution features, mapping near-surface geology and bedrock profiling, unexploded bomb or ordnance detection, assessing the condition of roads, soil mapping, locating rebars, bridge inspections, mapping rail ballast variations to name just fourteen or so (Iâm not including oil, gas or mineral exploration here ...). There's probably a few more listed on our website.
In my defence (and echoing another thread as to what might or might not be defined as archaeology) I would say that any thing buried and of an anthropogenic nature would to my mind count as 'archaeology'.....i.e 'underground storage tanks, buried foundations, old basements, mineshafts, mine adits and deeper workings, .... unexploded bomb or ordnance detection, assessing the condition of roads, soil mapping, locating rebars, bridge inspections, mapping rail ballast variations' confirm my prognosis. I accept that there are geological uses for geophysics, but would say in the main part these are on a macro rather than micro scale needed for specific archaeological use.
Free archaeology - Dinosaur - 10th September 2013
PhaseSI Wrote:Occasionally its down to site conditions but most of the time its bad data.
In one case it seems to be bad processing - on a large linear project most of the data is fine, but in some fields the data is clearly over-processed to the point of showing nothing...particularly galling in a field where a series of large ditches were stuffed full of tons (literally) of middle Iron Age smelting slag - but presumably additional spreads of slag in the topsoil had made the field so 'noisy' that it was processed out, losing any opportunity to determine distribution, sources (ie smelting furnaces etc) and indeed losing the ditches as well, so we've no idea what the excavated transect forms part of! [the whole field was geofizzed, over a much wider area than the excavation] Repeated requests for raw data drew no response... data's been paid for? or just the original report? Not the first time, and not from the first company
Free archaeology - PhaseSI - 11th September 2013
kevin wooldridge Wrote:In my defence (and echoing another thread as to what might or might not be defined as archaeology) I would say that any thing buried and of an anthropogenic nature would to my mind count as 'archaeology'.....i.e 'underground storage tanks, buried foundations, old basements, mineshafts, mine adits and deeper workings, .... unexploded bomb or ordnance detection, assessing the condition of roads, soil mapping, locating rebars, bridge inspections, mapping rail ballast variations' confirm my prognosis. I accept that there are geological uses for geophysics, but would say in the main part these are on a macro rather than micro scale needed for specific archaeological use.
Kevin. Quite a broad definition of archaeology there! And not one that would be agreed with by most people outside of archaeology (and possibly not all within?
). But agreed, if relatively modern pipes and cables, reinforced concrete, rail ballast etc are considered archaeology then there aren't many other applications for geophysics. Other than the soil mapping, near-surface bedrock profiling, finding solutions features, etc, etc.Dino. Presumably these 'geophysics' companies aren't being used by your company any more and if you suspect there were deficiencies in the survey these were reported and addressed by the planning archaeologists and consultants involved? If they didn't provide an archive of the raw data did that mean they didn't meet a specification / WSI?
Unfortunately the state of play in archaeological geophysics is as bad, and some would say worse, than in the rest of commercial archaeology. There are some companies who are cheap but do not actually have the necessary expertise and experience to do the work properly and use staff who are not properly trained. Its (relatively) easy to walk up and down a field but much more difficult to get consistent reliable data. Many companies who now do geophysics are totally fixated on getting coverage regardless of data quality. Unless the companies who are doing the sub-standard are pulled up on it by the company who hire them, the consultants and or the planning archaeologists then they'll keep doing it. Rant over and apologies to anyone reading this who were interested in the 'free archaeology' discussion!
Free archaeology - Dinosaur - 11th September 2013
Drawbacks of projects where working to an exterior consultant, we get what we're given
Conversely, one well-known geofizz outfit has invariably been helpful over the last few decades, to the extent of occasionally finding and reprocessing 20+ year old data for us (from floppies?...)
Free archaeology - Jack - 13th September 2013
Yep, yep and yep. All good points.
Though can't help prodding a bit more.
What constitutes significant archaeology can vary from situation to situation, site to site, region to region.
And yes topsoil, or to be more precise, what is in it can be significant archaeological remains requiring recovery and recording in some areas.
See the EH Research Strategy for Prehistory.......though not sure how widely it has been spread as yet (we got a consultation draft).
Some jobs require mitigation of the loss of worked flint from the topsoil prior to the development going ahead.
As many will know, mathematical modelling is dependent on the basic assumptions of the model (what is a site, what are the factors affecting its location, what errors exist in the data, what skewing factors exist). The proportion of the total dataset entered into any model will dictate its usefulness in predicting......just look at the climatic model for example.
Now I would argue that for archaeology we are still only looking at a small proportion of the total as a start, archaeology is only a proportion of past human activity.
Surviving archaeology represents a small proportion of the former total.
Known archaeology is only a tiny fragment of the surviving archaeology.
You just have to be involved in large projects in areas where DBA's used to come up with nothing, like the Holderness plain in East Yorkshire, South Yorkshire and the 'missing' Iron Age of Durham to get an idea of just how little we know about even simple distributions of most 'sites'.
This is not meant to be insulting Doug, as if you've been studying this for 40 years you must know this. I am fascinated by your claim and want more elucidation, if that is possible.
In my experience of site prediction when for instance being involved in preliminary archaeological works on pipelines, there are rules of thumb that are useful. But people are, and were, contradictory, arsey and stubborn. Sites always seem to crop up where unexpected.
I am interested in how you test your model.