Interactive 3D Lidar models in Sketchfab

Getting 3D models of Lidar data from QGIS onto a model sharing site such as Sketchfab used to be a hassle, with a number of steps as described here:

All this has changed with the 3.x release of QGIS.  The Qgis2threejs plugin has been revamped, with a new viewer, and the option to export 3D models to the glTF format.  Luckily supports .glTF files, and so the files exported from QGIS can be directly uploaded to Sketchfab without any intermediate steps.  Here are some basic instructions (in this case making use of QGIS 3.2).

  • In QGIS, make sure the Qgis2threejs plugin is loaded
  • Add a surface model dataset created from Lidar data to the map [eg a Digital Surface Model (DSM) or a Digital Terrain Model (DTM)]
  • Add any other datasets (eg a hillshade) to the map.
  • Click on the Qgis2threejs button 
  • In the dialogue that opens, in the DEM section, tick the surface model.  A 3D view of the map should appear, similar to that shown below:

  • Use Scene > World settings to change the vertical exaggeration.  There are other settings that can be played with.
  • When you are happy with the scene, choose File > Save Scene As > glTF (.gltf, .glb).  Save the file.
  • The upload button in Sketchfab can be used to directly load the .gltf file.
  • Here is a screenshot of the model in Sketchfab
  • And here is the finished model (with a few annotations added in Sketchfab):



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It was perfect weather for the annual AVAS BBQ last night, and we had a great turnout.  Thanks to Vanessa and Rachel and family for preparing the fantastic spread of food, and to Mark for providing the great riverside location.  Here are a few photos, there are more on the AVAS Flickr photostream.




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AVAS Newsletter

A selection of past issues of the AVAS newsletter are now available on the main AVAS website.  They can be accessed on the AVAS Newsletter page.

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Re-visualising a long barrow near Old Sarum

A few weeks ago I was walking around the ramparts of Old Sarum hillfort when I spotted the cropmarks of a long barrow, and adjacent ring ditches, in one of the fields to the north of Old Sarum.  These cropmarks are shown in the photo below:

Long barrow and ring ditch crop marks, Old Sarum

I knew the long barrow had been surveyed back in 1978, and I found the original geophysics report on the Historic England website .  Unfortunately, the plot of the survey results was missing from the PDF report, and so I was unable to compare the crop marks with the geophysics results.  I contacted Historic England, and the Geophysics Manager Paul Linford kindly arranged for the original paper plot to be scanned and added to the PDF report.  Paul commented that the 1970s technology wasn’t up to displaying the results as well as modern computer visualisations, but that the ditch anomalies could still be seen on the plot.  Here is a copy of the plot as scanned:

Original scanned plot of magnetometer results

I found it difficult to draw my own conclusions from the plot due to the pencil annotation, so I spent a short time in a graphics package digitally rubbing out the pencil annotation, as shown below:

Scanned plot with pencil annotation removed

Now the annotation was removed, it was easier to draw my own conclusions from the results, but also it was obvious that some of the anomalies relating to the long barrow were far from clear.  In particular, the long barrow ditches were barely discernible.  I thought it was a pity we didn’t have the original survey readings, from which we could have generated modern day visualisations.  That gave me an idea; what if we could reverse engineer the readings from the scanned XY trace plot?  It was worth a try.

So I set out experimenting with the latest GIS software to see if this was possible.  Here is a high level summary of the steps I went through:

  • Extracted the trace plot as an image from the PDF report.
  • Converted the image to a 1 bit (black and white) image.
  • Georectified the plot so the survey squares were perfectly square.  This was required because the original paper scan was slightly warped.
  • Thinned all line work on the image to single pixel lines.
  • Converted the single pixel lines to line geometries (ie collections of XY points).
  • Tagged the lines with their y index in the plot.
  • Batch created lots of vertical lines at known locations along the x axis.
  • Intersected the vertical lines with the trace lines to get a ‘reading’ from the trace.
  • Standardised the readings for each trace line by transforming to a common axis.
  • Wrote out the XY values to an XYZ file.
  • Imported the XYZ file into Snuffler (a geophysics data software package) and used the visualisation tools to produce a greyscale plot.

When I opened the final file in Snuffler, I was amazed to see that the process had been successful.  I had managed to reverse engineer the relative readings from the trace plot, to produce this:

Reverse engineered greyscale plot of magnetometer results

Continue reading

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Members Evening – Flint!

We are hoping for a good attendance at our members evening on Wednesday 3rd January 2018.  Steve and Chrissie have kindly offered to host an evening of flint!  They are going to bring along examples of flint tools, allow us to handle them and teach us how to recognise different varieties of worked flint.  It should be a really interesting evening.  Below is a poster for the evening, and we hope to see you there.

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A lost long barrow rediscovered?

In a previous post, I described an initial survey which aimed to look for a lost long barrow near Sopley.  The barrow was apparently bulldozed by American troops in WW2 to make way for Winkton airfield.  The first survey took in two 20m squares, and although inconclusive, gave a tantalising hint that there may be a large feature which potentially continued outside the survey area.

Yesterday, members of AVAS and The Christchurch Antiquarians returned to the site to extend the survey area.  Conditions were challenging, with numerous trees and bushes to navigate around.  However, the results were amazing, as shown below

The image above shows a large high resistance feature, shown in white and light grey, which appears to have a curved end to the south.  This feature is about 65m in length.  The shape of this feature suggests it is man made Continue reading

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Searching for a lost long barrow

On a web page recording memories of Winkton airfield, near Sopley, there is the following reference to the blatant destruction of a barrow to support the war effort:

“Apparently the site of the airfield contained an old burial mound, a barrow, claimed to be the site of the burial of warriors killed in a local battle between the Danes and King Alfred’s forces. The barrow was flattened during the preparation work for the aerodrome and Canon Kirkham expressed some concern at this to the commanding officer of the unit concerned. The officer was apologetic and offered to put it back again !!!”

At that time it was popular to attribute such barrows to the Danes or Saxons, but it is more likely that this barrow was Neolithic in date.  Sue Newman has uncovered further documentary evidence, including the following extract from the Gentleman’s Magazine 1861 describing activities of the Christchurch Archaeological Society:

“A barrow of seventy yards in length, and twenty yards in breadth, in the neighbourhood of Dane-rout, or Danat Lane, in the Clock-field on his property, will be opened by him in the course of the spring.”

The old OS maps of the area show an interesting long thin enclosure, of similar dimensions, in a wooded area called Clockhouse Copse.  This copse was truncated on two sides when Winkton airfield was built, and the area of the enclosure is in the part of the copse that was destroyed.  This can be seen in the maps below.

The trig point within the enclosure is also of interest, as these were usually located on raised ground.  Sue Newman has also discovered that on the tithe map for the area, the field surrounding this enclosure was called ‘Burrow Close’, possibly a derivation of ‘Barrow Close’.

Given this evidence, AVAS recently undertook a joint survey with The Christchurch Antiquarians to Continue reading

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Hampshire Field Club Proceedings available online

Hampshire Field Club and Archaeological Society have recently made their proceedings available online.  Volumes from 1920 to 2014 are available as PDFs, with links available on the main Hampshire Studies web page.

Some highlights include:

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Gradiometer survey of second mound

We were extremely fortunate with the weather yesterday whilst carrying out further survey work on the second possible long barrow (see Promising results from second gradiometer survey).  Progress was slow due to barbed wire fences and hedges crossing the survey area, as well as very rough ground.  Partial squares tested our ability to add dummy readings and dummy lines, but all worked out fine.

We have gradually added more small areas to the survey of this mound, and the picture is beginning to become much clearer, as shown below:

Gradiometer results for second mound

Gradiometer results for second mound

The width of the survey data is 80m.  There is a wide feature that flanks the mound, and which looks like a northerly ditch.  Things are less clear to the south.  A barbed wire fence crosses horizontally across the centre of the plot.

After finishing that survey, we thought we would try to locate a small ring ditch in the adjacent field, recorded as having an unusual shape.  With an imprecise coordinate, and an imprecise GPS position from my phone, we missed the feature completely in our first 20m square, but were successful second time around:

Small ring ditch

Small ring ditch

It isn’t that remarkable, although appears to have a gap to the west.

Today I returned the gradiometer to the New Forest National Park offices in Lymington, which draws to a close our survey work for now.  I thought it was worth including the surveys of our other sites in the fields adjacent to those above, as we are very pleased with the results.

Here is the survey from the first mound, which has all the indications of a classic long barrow.  The width of the plot is 80m.

Long barrow 1

Long barrow 1

Here are the results from the double ring ditch:

Double ring ditch

Double ring ditch

I have uploaded some photos to the AVAS Flickr site, here is one example:

AVAS Geophysics 13 Nov 2016

Thanks to everyone in AVAS for helping out with the surveys, to Bournemouth University for the load of the equipment, and to the New Forest National Park Authority for arranging the loan of the equipment.





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Promising results from second gradiometer survey

Last week we undertook our second gradiometer survey using the gradiometer loaned out by Bournemouth University as part of the LoCATE project.  The survey site was a second ploughed out mound about 200m north of the site of our first survey.  The first survey had indicated rather conclusively the site of a long barrow;  a second long barrow in close proximity would be a significant and unusual find.

This survey was much more difficult than our first.  We had just calibrated the meter when thunder rumbled and there was a heavy downpour.  We also had to contend with a barbed wire fence cutting the site in half, as well as partial grid squares caused by field boundaries, hedges and thick vegetation.  We had to work quickly given the looming black clouds.

Given these difficulties, we are very happy with the initial results, as shown below (plot dimensions are 60m x 40m, north to top):

Gradiometer - second mound

Initial results for mound 2

We were only able to survey the eastern part of the mound.  It is possible to discern a clear, regular anomaly which curves around to the east and then travels in straight lines westwards at the top and bottom.  These lines appear to be starting to converge, suggesting a tapering anomaly which reflects the general shape of the mound.  The strong black and white horizontal disturbance across the middle of the plot represents the barbed wire fence, and there is a very strong white anomaly in the top part of the plot which we are currently puzzled by.  The red parts of the plot represent areas we did not survey.  The wide dark anomaly above the curving anomaly could represent the terminal of a wide ditch;  we will need to extend the survey area to the north to investigate this further.

In conclusion, these results are less conclusive than those for our first survey.  However, the regular nature of the anomalies suggest that we are dealing with a man made rather than natural mound, and the general pattern is certainly conducive to an interpretation of a second long barrow.  How exciting if we can prove this!  We now plan to extend the survey area where possible to investigate further this theory.  We will also consult with the resident experts at Bournemouth University for their opinion on the results.

Thanks to :

  • everyone who helped with the survey
  • Bournemouth University for loaning out their equipment
  • the New Forest National Park Authority for coordinating the loan of the equipment


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