26 December 2014

Version 1.14 of Snuffler released

My last post of the year will be for an update to my geophysics software, Snuffler. The new feature this update is an extension of the support for RM15/MPX15/RM85 multiplexing. As well as doing parallel readings, this update will now cope with readings on multiple levels. It is a bit of a nasty hack as far as the user interface is concerned, but it works. Here's how :

Normally, you download your data into an import file, then export from that into grids. Job done. With multiple levels of multiplexor data, there is an extra stage in the middle. In the initial download, you select the total number of readings recorded each time you put the probes in the ground. For example, if you record two readings with 0.5m probe spacing and one reading at 1m probe spacing, that would be a total of three readings at each point.

When you export from this import file, rather than getting grids, you will be asked which readings you will be exporting at this level, creating a new import file containg just the readings at that level, from which you export grids in the normal way. In the above example, you would create two new import files from the original import file. The first file would contain readings one and two and the second file would contain reading three. Full details on how to do it properly are listed at the bottom of the Import Files section of the help file.

I didn't have access to a machine when developing this, so it may not work perfectly. If you try this yourself and do have problems and the help file is not being helpful, please let me know. Many thanks to two of my users, Helen and Manuel, for helping me test this.

You can download the new version at the usual place.

08 December 2014

Latest Results: Ovingdean

Brighton and Hove Archaeological Society are a very active group fieldwork wise, with an insanely long digging season and a lovely supportive approach to new diggers. It was with BHAS that I started doing geophysics, with Bill Santer teaching me how to do earth resistance. Bill sadly passed away this year, so I would like to dedicate this survey to him, the fantastic bloke who started me on this path. He will be sorely missed.

The site that BHAS have been digging this year is at Ovingdean, where there is a medieval manor complex within an earthwork enclosure next to the church. They have done a few seasons of excavations here on one side of the enclosure, based on some earth resitance they did before I started doing archaeology. They have excavated the main manor house, which has very chunky walls and an undercroft, and this year they have been excavating what looks like a post built barn structure next to it. There is still the other half of the enclosure unexcavated, and BHAS wanted to know what was there.

First, the original earth resistance, flattened with a high pass filter so you can see the main manor building amongst the rubble near the churchyard wall to the south-east. A trackway snakes through the middle of the enclosure from an entrance in the south-east and possibly out the other side to the north-east. To the north-west, parts of the enclosure revetments and bits of masonry buildings up against the earthwork enclosure can be seen.

Earth Resistance. Click for a larger image.

This year's surveys include magnetometry and GPR. Being chalk, the magnetometry results are predictably rubbish, but do show hits of the enclosure to the south-west. Much of the north-west part of this survey is obscured by the magnetic halo of a large water unfortunately.

Magnetometry. Click for a larger image.

The GPR was a lot more productive, showing what looks like an open sided barn and an attached dovecote against the north-west enclosure earthwork. Signs of the outer enclosure revetment are visible in other layers further down.

A single GPR slice. Click for a larger image.

05 December 2014

NSGG Conference 2014

The time came once again to attend the Near Surface Geophysics Group conference, which is held every two years, the last being in 2012. As always, the chats in between lectures were the best bit. My ego was thoroughly strokes by three people coming up to me out of the blue and complimenting me on Snuffler. It's a wonder I got my head out of the door at the end of the day. I also spoke at length to Erica Utsi to enquire about attaching my forthcoming purchase of survey grade GNSS to my GPR.

The talks were many and varied. There were 12 of them! My favourites were :

Kris Lockyear talked about getting community archaeology groups involved in geophysics and some of the results they had. The survey of part of Verulamium. A grant bought a fancy mag cart, which seem to be everywhere these days, which the various groups share, with training days on how to use it. This sort of work is excellent for getting smaller groups who otherwise would not have access to geophysics. They have an excellent blog.

The talk I was most looking forward to was Armin Schmidt (of course) talking about inversion modelling for magnetometry. It seems the subject is a lot more subjective than I imagined, with various models of 3D interpretation potentially fitting the 2D data. I asked where I could find out more about how this was done, as I was thinking of incorporating this into Snuffler. The ripple of laughter that went around the room suggests that this is a black art best left to the damned.

Pope-Carter (I think) spoke about some open source software for geophysics being developed in python by students at Bradford called ArchaeoPY. It was explained that a lot of the work of writing display stuff was already done and available in easy to use python libraries. A lot of the functions already available in the software were shown. The whole thing is impressive and has a lot of potential. Being open source, if there is a feature you think is missing, you can go ahead and add it yourself!

There were two interesting talks from overseas. Someone from Italy talked about the sites found there, including GPR over a proper Roman road with kerbstones and all, which was very nice to see. I do like a bit of Roman. Someone from Canada produced some actually really good plots using EM of buildings, probably because the remains were shallow. Perhaps EM isn't so bad after all, or maybe you just have to do it at the insane resolution that they did. Both speakers lamented the lack of understanding of geophysics there by the relevant cultural authorities.

More Roman from the Canterbury Hinterland Project, both close to me and Roman, my favourite. It is run by institutions outside of Kent, since no-one in Kent seems to do geophysics. Some of the buildings they found using high res radar were quite impressive, and odd looking. There was also an interesting attempt to clean up the rather messy GPR data, using a different method than Armin suggested two years ago. I think this was my favourite talk of the day.

Then, of course, there was the usual posters, many more this time around. The judging was by popular vote rather than the usual panel, so I'm wondering if it will end up a bit like the Eurovision Song Contest with everyone voting for their mates. I certainly did :)

Hardware wise, mag seems to be heading for multi-sensor carts, some of which were evident in the talks, posters and commercial exhibitors. The greater speed and resolution can only be a good thing. I just don't understand how people afford these things.

All in all, another good year.