Tag Archives: Roman urbanism

The final results from Alba Iulia (Apulum)

We managed the final ten squares on the last day completing the area I hoped we would cover. We managed 2.6ha in seven days of survey.  The final four grid squares had an old excavation trench in the middle of them and a sea of mud from the spoilheap being bulldozed back into the hole.

Fig. 1: Stefan and Wyatt surveying in the mud.

I have left the grid on the next image (Fig. 2) which gives you some sense of scale.  The grid squares are 20x20m, and site north is to the right.

Fig. 2: the surveyed area with grid for scale.

In the next image (Fig. 3) I have labelled a few of the features.  One can easily see many of the buildings.  Because of the large differences between areas of low readings and areas of high readings I have applied a log-transform to the data to make some of the features more visible.

Fig. 3: the 0.5m survey with log-transformed data.

An alternative (and very common) method of evening-out the differences is to apply a high-pass filter (Fig. 4).  The downside to this is that areas of very high readings will often end-up with a area of very low readings next to it which are purely an artefact of the filter.  It is essential, therefore, to have several images and compare them so that you do not create features where there are none.

Fig. 4: the data after the application of a high-pass filter.

As well as the main survey with a 0.5m probe spacing (thus ‘looking’ 0.5 to 0.7m below the surface, approximately), we were simultaneously collecting 1.0m probe spacing data (which ‘looks’ about 1.0m into the ground), but at only two readings per square meter rather than four.  This extra data did not add that much more to the survey (Fig. 5), but does make the north-south road show more clearly.

Fig. 5: the 1m probe spacing data, high pass filtered.

There is quite a bit to do in terms of interpretation and drawing-up maps of the results, but I am very happy with the new results which have greatly improved an already excellent set of results from 2002/3.

The journey home seemed to go on for ever, but at least I had some entertainingly-named beer on the way!

Fig. 6: Munich Hell.

Many thanks to the whole team, and especially to Stefan, Wyatt, Doru and Ian.

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Somewhat tired

On Friday the snow kept on coming and we had to abandon the survey for the day. It gave us the chance to explore the citadel and visit the museum.

Fig. 1: Carol’s Gate, Alba Iulia.

The snow had stopped yesterday morning so we headed out to site once more. During the day the snow cover slowly melted and we managed an excellent eleven grids, although two of those were small partials.  Today, the weather improved…

Fig. 2: Stefan surveying.

I even ended-up with sun-burnt ears!

Having lost time through airline incompetence and snow, we were determined to try and catch-up and we managed twelve 20x20m grids at 0.5m intervals with just the two of us.  To say our feet ached would be an English understatement.  We did, however, get some lovely results.

Fig. 3: the half-meter probe spacing survey at the end of Sunday.

We believe that the thin line on the right hand side of the plot running diagonally is the line of the town wall.  We seem to have picked-up a set of three small buttresses on the inside of the wall.  We have some more buildings at the top of the plot.  Obviously, there is a great deal going on in this data and a detailed interpretation will take a little longer.

Tomorrow our target is the ten grids along the top edge of the survey to complete the block and join the survey up with the earlier excavations.  It is tempting, however, to try and survey a little more at the top to see what those two pairs of parallel lines are doing!

I’d like to thank the whole team but especially Stefan who has worked really hard, and Wyatt who has also helped a great deal, and also Ian Haynes and Doru Bogdan who made the whole trip possible.  The whole team have been great to work with and made what could have been a trying experience great fun.

Of snow and sheep

Yesterday started off well. The weather was a little cold, but other than that it wasn’t too bad.  Then it started to snow.  The snow was OK, not too much.  Then it snowed some more.  And a bit more…

Fig. 1: surveying in the snow.

Just to add to the delights, we had a visitation from some sheep.  They charged past me where I was laying in the grid for the next square, and surrounded the team using the res.

Fig. 2: The sheep visit the survey.

Fig. 3: The sheep visit the survey (heavily cropped photo).

By lunchtime, it was getting silly, and we packed-up.

Fig. 4: Getting silly.

We did, however, get some very nice results from both the 0.5m probe-spacing data and the 1m -probe spacing data (the latter “looks” a bit deeper into the soil).

Fig. 5: the 0.5m probe-spacing data.

Fig. 6: the 1m probe-spacing data.

The dark line running diagonally across the plot is a Roman road with a subsidiary road running off it at an angle.  The excavations were at the far left-hand side of the image.  The buildings along the road are pretty clear.  Both these images have been high-pass filtered to bring out the structures.

Although the landscape is covered in snow, it isn’t actively snowing at the moment, so I suspect we will be going out again today.

Day 54

Anyone new to this blog or geophysics in archaeology is recommended to read the material on the “Geophysical survey in archaeology” page.

Yesterday was the last day of the 2017 season at Gorhambury. Apologies for the slight delay in posting… we went down the pub for supper!  We have completed 54 days of survey at Gorhambury over the three seasons.  As well as the 35.7ha of magnetometry we completed last season, we have now completed 14ha of GPR survey.  Just pushing the machine along the strings is about 280km.  We didn’t manage any usable Earth Resistance survey in 2015, but we have done quite a bit in 2016 and 2017.  Last year we had terrible problems with the very hard and dry soil.  As a result, many grid squares have been done twice.  We have, however, completed a 5.6ha survey at 0.5m intervals.  That is 224,000 resistance readings, or sticking the machine into the soil 112,000 times.  That doesn’t include three days with the beast which is a further 9,600 survey points resulting in 67,200 readings.  Here is the story in pictures.

Fig. 1: crude mosaic of GPR time slices showing the extent of the survey so far.

Fig. 2: the 2016 and 2017 Earth Resistance surveys at Gorhambury.

Figure 1 shows a (very crude) mosaic of time slices for Gorhambury just to show the entire extent of the survey.  There is going be a great deal of work reprocessing these to get the best out of them and to get the various blocks to match.  I also need a faster computer.  I tried out the kriging option last night and it took several hours to process the data, but the images were no doubt sharper.

Figure 2 shows the 2016 and 2017 Earth Resistance surveys.  At the moment the two seasons are just images put together in Google Earth.  I need to see if I can join the two into one big survey and get the edges to match properly.  I also need to see if I can get rid of the line caused by the deluge this season.

Firstly, let us look at the Earth Resistance survey results.  On the last day we redid four squares from last year, and then completed five awkward partials around the corner of the enclosure for the theatre.  Why did we redo those four?  Figure 3 shows last year’s survey with the block marked.  The hot dry conditions gave very noisy and unsatisfactory results.  I thought it was worth a morning’s effort to get those re-done.

Fig. 3: the 2016 resistance survey showing the duff grids.

Now the improved grids.  Note that the slight difference between the two surveys is due to minor differences in how I processed the data.  I will produce a more standardised plot.

Fig. 4: detail of the area surveyed at the end of the 2017 season.

Fig. 5: the Earth Resistance survey with the blocks from 2017 high-pass filtered.

There are some interesting things happening at the north-eastern corner of the plots, and into the area to the north we haven’t surveyed.  My guess is that the stratigraphy is probably deep and complex in this area.  Let us compare this area to the magnetic data (Fig. 6) and the GPR data (Fig. 7).

 

Fig 6: the magnetic survey with the area of the Earth Resistance survey from days 17 and 18 indicated by the cyan outline.

Fig. 7: the GPR survey with the 2017 Earth Resistance survey area indicated in red.

Fig. 8: the GPR survey with the res data overlain on it.

From all three data sets we can see that there is a lot going on in that bit of the field near the drive and the theatre, but it also appears there has been a good deal of robbing to add confusion to the picture.

How about the GPR team?  A month of nice weather with a bit of rain has made the grass green and lush.  Lovely for sheep, but a pain to push the GPR through.  They completed two 40x40m grids on a hot humid day, excellent progress in the conditions.

Firstly, here are a set of time slices (Fig. 9).

Fig. 9: GPR time slices from the area surveyed on Day 18.

The vast majority of the area surveyed appears to be empty.  There are hints of earlier agricultural practice but not much else apart from the top edge where part of a building can be seen.  This connects to the area surveyed earlier in the season.  I reprocessed the earlier version of that block today using kriging to give a sharper image.  Here are the slices together (Fig. 10).

Fig. 10: the GPR survey from day 18, along with a re-processed block from day 12.

We clearly have a nice L-shaped building.  I suspect this is Insula XXX, Building 4, Niblett and Thompson Monument No. 461 which is known from aerial photographs from 1976.  They only have part of the plan, however, and ours looks quite different (hence my doubts).  The mag data shown in Fig. 11 shows some slighter, more ephemeral buildings to the SW along the line of the SW-NE street 25 which can be seen very easily.

Fig. 11: the mag data in the area of the GPR survey.

The SSW–NNE running street 25 which runs along the NW side of the building we have been discussing, shows very clearly indeed but street 10, which is supposed to have run WNW–ESE just to the south of our new building and the “House on the Hill”, does not show at all in either the mag or the GPR data.  It was observed in excavations by Frere near the modern road, but not this far west.  In terms of the town plan, we seem to have two lines of buildings running SW-NE, one along Street 25, and another along street 23, but a large open area with nothing very much it in apart from a few quite large pits.  One can almost see some alignments in those pits.  Are we seeing backyard areas divided into blocks?

Although our season at Gorhambury has come to an end, we will be undertaking surveys elsewhere, and probably in Verulamium Park once more.  I started this posting with some numbers, so I thought I would end with some as well.  This is the 131st posting on the blog.  Those postings take-up 583mgb of our 3gb free allowance and include 693 images.  There have been 68 comments, but we have been protected from 9,402 pieces of spam!  The blog has been viewed 32,150 times by 11,016 separate visitors (in practice, this means that number of IP addresses).  Our best month was the first season at Gorhambury in 2015.  This August has been down on the previous two (2015: 1.8k, 2016: 1.7k and 2017: 1.4k) but the average number of visitors per day has gone-up over the year and we are likely to reach 9,000+ views by year’s end.

I would like to thank everyone who helped this season once more, both with pushing machines, moving strings, laying-tapes and moving equipment.  You are all stars in my eyes, and I think we have created a stunning survey.  We all got a bit tired towards the end, especially in the rather hot and humid conditions over the couple of days, including CAGGs loyal follower, Fergus (Fig. 12).

Fig. 12: Fergus sleeps off a busy day on site.

If anyone is interested in joining in with some of CAGG’s activities, drop us an email.  We are a friendly bunch, and on-the-job training is given.

Buildings galore

Anyone new to this blog or geophysics in archaeology is recommended to read the material on the “Geophysical survey in archaeology” page.

Before looking at today’s results, I thought everyone might be interested in seeing the reaction to our survey at Verulamium at the Near Surface Geophysics Group conference last December. Not being someone who twits, I hadn’t realised that a webpage of postings from the conference had been put together at https://storify.com/girlwithtrowel/tweets-from-the-nsgg-recent-work-in-archaeological You have to scroll down a long way, but look out for the comment by Magnitude Surveys.

Today saw the GPR crew tackle an awkward block that has the hedgerow half way across it.  Here are nine time slices from it.

Fig. 1: Nine time slices from the survey on day 17.

There are some very clear buildings.  Look, for example, at slice 7 (right hand column, middle slice).  In proof of the only universal law, look at the first “sawtooth” on the south side of slice 8 (bottom left hand corner).  There is a lovely little apse just peeping out into the plot.  Typical… the building is under the hedge.

Let us see where this block fits in the overall GPR survey (Fig. 2).

Fig. 2: all areas surveyed using GPR at Gorhambury. Today’s block is in colour.

The absolute area we have now surveyed is quite impressive thanks to the efforts of members of CAGG.  Well done all.  Let us now have a look at a couple of time slices from today.

Fig. 3: GPR time slice 4 from the day 17 survey,

The fourth time slice (Fig. 3; roughly 0.4 to 0.5cm below surface), mainly shows the road running diagonally SW to NE.  The cross-roads just to the north of today’s block is a very busy locality with lots of buildings clustered around it. The block just to the south of today’s survey also has some pretty substantial buildings.

Fig. 4: time slice 8 from the GPR survey on day 17.

Time slice 8 (Fig. 4, roughly 0.8 to 1.0m below the surface) shows some of the buildings alongside the road to the south of the hedge line.  The road is squeezed in between the building found earlier in the block to the south and the new rooms found today.  We also have a little more of the building to the west.  The two lonely walls in the southern block would seem to be related to that building too.  All-in-all, some very nice results.

The Earth Resistance team of Ellen, Pauline and Graham headed north to tidy-up the top-edge of last year’s survey.  They managed a surperb eight 20x20m grid squares.  Here are the results.

 

Fig. 5: Earth Resistance data from day 17.  The pink line marks the 2016 survey.  The lone grid square on the northern edge was re-surveyed.

Fig. 6: the Earth Resistance data from day 17, high pass filtered.

As can be seen, especially from Fig. 5, we have picked-up some more details of the nice large building in the middle of the plot, as well as other buildings such as the small one at the western end of the strip of grid squares.  At the eastern end we have a large square high resistance feature.  A surviving floor, perhaps?

Fig. 7 shows the mag data from this area.

Fig. 7: the mag data from the same area as Figs. 5 and 6.

Not much sign of the small building to the west, or the “floor” to the east in the mag data, although the “floor” seems to be associated with quite a few walls.

The “sinuous ditch” cuts across the line of today’s plot (seen as the broad dark linear feature entering Fig. 7 top centre, and heading to the SE).  This is almost certainly the town aqueduct as it lies along the 300ft contour. Comparison to Fig, 8, however, shows we we do both mag and res…  no sign of the aqueduct in the res data at all.

Fig. 8: today’s Earth Resistance data overlain on the mag plot.

One last push tomorrow and we are “done” at Gorhambury for 2017.  Many thanks to everyone who has worked so hard, and also thanks to the Earl of Verulam for allowing us access.

 

Just two more days

Anyone new to this blog or geophysics in archaeology is recommended to read the material on the “Geophysical survey in archaeology” page.

I did consider using antepenultimate again, but I thought you might think me pretentious…

Everyone worked extremely hard today.  Mike and Jim on the GPR finished yesterday’s block and managed another 40x40m grid square.  No easy task over the long grass and thistles.  Ruth, Dave and Julia completed five earth resistance squares, including two that had to be done in two parts and joined together in the software later due to an inconvenient hedge!  Good job everybody, and many thanks.

Here is the Earth Resistance survey, both normal, high-pass filtered, and the magnetometry data from the same area.

Fig. 1: the Earth Resistance data at the end of day 16.

Fig. 2: the Earth Resistance data at the end of day 16, high pass filtered.

Fig. 3: the magnetometry data for the area shown in Figs. 1 and 2.

I hate to say it, but our five squares, including the two annoying partials, appear to lie between the buildings along the road to the north of the hedge line, and to the north of the buildings we found yesterday. We do, however, have a nice tidy area surveyed now.  We couldn’t have left quite such a silly hole in our survey data.  Tomorrow we head north to survey along the northern edge of the block we did last year.

The first block of GPR data from today was a continuation of yesterday’s

Fig. 4: the GPR time slices from the block completed on day 16.

Nothing very exciting jumps out from the plots, although there are some things to check out.  Slice 6 (second from top on left) has a strange upside-down M shaped feature (in black) and slice 8 (bottom-left) has something semi- or sub-circular near the northern edge.

How about the second block?

Fig. 5: the GPR time slices from the second block completed on Day 16.

Not a great deal there either.  Sorry guys!

Tomorrow sees the GPR crew filling-in an odd gap between last year’s survey and this years.  The plus side is that the mag shows lots of buildings, so tomorrow’s results ought to be much more interesting!

Many thanks to everyone who worked so hard in the sun today.  Just two more days.

Templeless

Anyone new to this blog or geophysics in archaeology is recommended to read the material on the “Geophysical survey in archaeology” page.

The rather odd title will become clearer! Today saw Graham, Dave and Ruth on the Earth Resistance meter, Jim, Mike and Robert on the GPR, and myself rushing around with the dGPS. I managed to find time to do a little topographic surveying, the purpose of which will be revealed in due course.

First, the resistance survey.  The team managed an excellent seven 20x20m grid squares.  Thankfully, all whole grids today, although we are back in partial-land tomorrow.  Here are the “normal” and the high-pass filtered versions of the data.

Fig. 1: Earth resistance survey at the end of day 15.

Fig. 2: Earth resistance survey at the end of day 15, high-pass filtered.

Two things can be seen from today’s survey.  Firstly, there are some nice buildings showing on the western edge of the survey area, especially in the ‘sticky-out’ bit (technical term that) which was the last grid square we did.  They show great.  The second thing that arises, is: what on earth is going on the the south-west corner?  The irregular lines of high resistance running down slope from SW to NE do not look like archaeology, so are either geology or erosion.  Very curious!  I need to drape the results onto a topographic map (probably the LiDAR data) to see what the relationship is.

The mag data (Fig. 3) also shows the buildings on the west, but not so clearly.

Fig. 3: Mag data in the same area as Fig 1 and 2. The 2017 survey area marked in red.

The strong linear things in the SW corner do not show at all.  In fact, it is rather bland!

Lastly, the GPR data (Fig. 4).  Please note that the image is made of a variety of time slices created by two separate systems. Eventually, I will process it all to make a nice clean image, but this will do for now.

Fig. 4: GPR data in the same area as Fig 1 and 2. The 2017 survey area marked in red.

Interestingly, the plans of some of the buildings look clearer in the GPR than the res, and for others it is the other way around!  The “muddier” looking walls in the western side of the GPR plot are because I am using inverse weighting to interpolate the results as the kriging in the new software is impossibly slow. The old software’s kriging routine was much faster and gives crisper looking walls.  I probably need a faster computer!

The GPR team finished one block they started yesterday, and started a second block today.  Here are the slices.

Fig. 5: GPR survey time slices. Yesterday’s second block and today’s first block.

Fig. 6: GPR survey time slices, today’s second block.

You can be forgiven for being underwhelmed by the results.  I am a bit puzzled.  The radargrams look quite busy in places, but the slices look very dull.

Now comes the explanation of the strange title of this post.  Let us first look at the slices in position (Fig. 6), and then at the mag data for the same area (Fig. 7).

Fig. 6: a crude mosaic of the time slices in Google Earth.

Fig. 7: the mag data in the same area as Fig. 6.

In Fig. 7 you can see a small square of in black on the lefthandside, probably representing a small square enclosure.  I had hoped this was another Romano-Celtic temple like the one we surveyed at Durobrivae.  Not much sign of anything is showing in the GPR data, however.  Shame!  I had hoped for a small temple overlooking the Insula XVI temple and looking across the valley to the one at Folly Lane.  Sadly, not to be.  The little square enclosure remains a mystery.

Many thanks to everyone who helped out today. Tomorrow is our antepenultimate day.  Fingers crossed for good weather.