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On Saturday 11th March 2017, we held a LiDAR Workshop for the Spa Ponds Heritage Project. Phil’s account of the day is below:

Welcome to the third in our series of accounts of the activities taking place as part of the Heritage Lottery Fund supported Spa Ponds Heritage Project. The day-long training session was led by David Astbury of MBArchaeology, who treated participants to a presentation that introduced us to the use of Light Detection and Ranging (LiDAR) for local history research. David is a PhD researcher at the University of Newcastle.

Part 1

The first part of the morning consisted of a comprehensive explanation of what LiDAR is and how data is obtained, processed, visualised, interpreted and finally transcribed.

Light Detection and Ranging (LiDAR) is an airborne mapping technique, which uses a laser to measure the distance between the aircraft and the ground. Up to 100,000 measurements per second are made of the ground, allowing highly detailed terrain models to be generated at spatial resolutions of between 25cm and 2 metres.

David’s introduction was similar to that available from: https://www.youtube.com/watch?v=eBUCGxZq_xg which is a good primer for those who could not attend the workshop.

David explained how the data is based on the number of ‘returns’ from the laser pulses generated by the plane. LiDAR cannot pass through objects such as leaves and tree branches but will pass between such obstacles until it hits the ground.

Examples were given where 4 ‘returns’ would indicate 3 levels of branches with the final return being the ground, thus mapping the height of the tree. This explanation was particularly relevant to our Spa Ponds site being largely tree covered.

LiDAR data is available to the public due to nationwide surveys undertaken by the Environmental Agency to indicate flood risk areas. The data does need quite complicated software to interpret the data but again this is freely available from: http://environment.data.gov.uk/ds/survey/

David continued by explaining, step-by-step, the types of data provided by LiDAR. Two main models use in this field are: the Digital Surface Model (DSM) and the Digital Terrain Model (DTM). DTM has the ability to ‘strip away’ the data collected from tree coverage to reveal the data reflected from the ground only.

David continued by explaining how data is processed using GIS. The OS provide a helpful explanation of their own at:
https://www.ordnancesurvey.co.uk/support/understanding-gis/what-is-gis-data.html

Simply put, a Geographic Information System (GIS) is a system designed to capture, store, manipulate, analyse, manage, and present spatial or geographic data.

Various levels of data can be placed on top of each other such as LiDAR, maps or aerial photographs. We were shown several examples of GIS output for the Spa Pond area and David explained how three different approaches can give different results. These were Hillshade Aspects, Composite Bands and Slope Data.

Hillshade data was particularly interesting as the software allows the computer to model how the image would adjust when viewed with sunlight approaching the site from several compass points. Composite Bands added colour to the images with each specific colour representing a geographical feature such as flat ground or slope.

David then moved to the Visualisation stage of the interpretation of data, where several sources of information such as LiDAR, Ordinance Survey maps, Google Earth and other aerial photographs, as well as images and information supplied by the Sites and Monument Records (SMR) or the National Monuments Record (NMR) work synergistically together to provide an understanding of the site. In addition to the SMR and NMR we now also have the Historic Environment Records (HER).

David ended the first session with an excellent demonstration of the 3D modelling capability of the software by ‘flying’ us through the Spa Pond site and providing remarkable views of the site from several elevations.

Part 2

An important message in this session was to never rely on LiDAR on its own. LiDAR should be used alongside a variety of sources such as aerial photographs, current and ancient maps, Google Earth images, and SMR/NMR/HER information.

LiDAR will only give data from objects above ground. Data from below ground can be obtained by using Geophysics technology. David recounted examples of wrongly interpreting LiDAR data where excited researchers found Stone Circles that turned out to be Mineral Railway lines and where old Roman roads turned out to be gas pipelines! Unfortunately, areas of ground that have been extensively ploughed in modern times will offer little to LiDAR.

Lunch

After lunch David introduced a practical session where he supplied a variety of LiDAR images of the Spa Ponds area. The group split into small working parties to analyse the different images looking for and sharing points of interest. This session was an ideal opportunity to use the skill absorbed during the morning session.

The day was brought to a close with a vote of thanks to David Astbury and MBArchaeology who had prepared and presented an excellent workshop where a particularly complicated scientific process had been presented succesfully to a group of LiDAR beginners. Thanks were also given to members who had enhanced the day by way of providing refreshments and taking photographs.

On Saturday 25th February 2017 we held a Research Skills Training Workshop for the Spa Ponds Heritage Project. Shlomo’s account of the day is below:

Welcome to the second in our series of accounts of the activities taking place as part of the Heritage Lottery Fund supported Spa Ponds Heritage Project. The day-long training session was led by Matt Beresford of MBArchaeology, who treated participants to a presentation that introduced us to documentary and archival sources for local history research.

Matt introduced some basic books for budding local historians, including one by Joy Bristow that features a glossary of words and terms that we might come across. For a list of recommended books and other research resources see: https://www.foresttown.net/index.php/heritageproject/research/

Moving on to more local sources, Matt recommended ‘The History of Mansfield and It’s Environs‘ (William Harrod, 1801) and John Beckett’s ‘Nottinghamshire Past’. Matt emphasised the importance of appreciating the site within its landscape. Books such as ‘The Making of the English Landscape’ by W G Hoskins and Francis Pryor’s ‘The Making of the British Landscape’ could help us contextualise Spa Ponds within its Mediaeval landscape.

Another takeaway message from Matt’s presentation was that digging around in old books can be just as valuable as digging in fields when it comes to understanding history.

Matt then led a discussion of the relationship between ‘local history’ and ‘archaeology’, explaining how these two disciplines often overlap. For example, we can find artefacts unearthed through archaeology stored in local history libraries.

Matt noted that historical records can also be found in unexpected places, like King’s Mill Hospital. The group discussed some of the places where we have come across historical information. For example, John pointed out that public houses can be useful places to glean information, whether from photographs displayed on the walls as decorations, or from those who frequent such establishments.

We were introduced to some of the many different types of sources of information that might be useful when researching the history of Spa Ponds, including: maps, manorial documents, historical directories, legal records, personal diaries, census returns, drawings and photographs, and oral histories.

For a list of research resources see: https://www.foresttown.net/index.php/heritageproject/research/

Matt warned us about some of the shortcomings of historical sources, including the way that maps are not always accurate and hand-written records are not always easy to decipher. 

Matt signposted us to the British Association for Local History (BALH) and the Nottinghamshire Branch of the Victoria County Historians, alongside the County Archives for both Derbyshire and Nottinghamshire, and the National Archives at Kew in London. No doubt we will be visiting all of these via the Internet, as well as wandering around some of them ‘in real life’ over the coming months and years.

The prospect of accessing historical resources brought with it a number of initial questions, such as:

• Who owned the area at the time of the Domesday Book (around 1086)?
• When was the deer park first established in Clipston?
• Where were the nearest manor houses, castles and other large buildings located?
• Was the hill above Spa Ponds used prior to it being part of Clipston Park, e.g. as an Iron Age hill fort?

These and other questions may be addressed during our group research sessions and as part of the forthcoming Interpreting Maps Workshop (which will take place on Friday 21st April) when we will be mapping all recorded archaeological finds in the vicinity of Spa Ponds.

After lunch Matt guided us through some activities that were designed to help prepare us for the sort of challenges we can expect to encounter as we begin to undertake research into the history of Spa Ponds and environs.

Matt ensured that we are equipped with plenty of good ideas about where we might go to find information, including Internet resources and those available only by visiting libraries, museums and other places where archives are kept.

A day overflowing with information and thought-provoking activities was brought to a suitable close by Phil, who thanked Matt for his contributions, as well as thanking those who contributed in other ways, e.g. Ann, who made sure there was plenty of fruit and other healthy nibbles.

We are all looking forward to the next Spa ponds heritage project events, including the Heritage Management Plan and group research session on Friday 3rd March, and the LIDAR Workshop on Saturday 11th March.