Thousands of Years Old or Cold War

From Tape Measures to VRS and Glonass

 

An instrument for every occasion! A Trimble 5600 Robotic Total Station is  on hand for when satellite reception is a problem. Using the newly acquired R8 at Scordale.

English Heritage has a wide-ranging role to understand, protect and promote the country’s historic environment for the benefit and enjoyment of all. Helping them achieve this is the Archaeological Survey and Investigation Team based at offices in Exeter, Swindon, Cambridge and York. The teams work across all periods, surveying everything of interest from prehistoric monuments thousands of years old to military installations from the Cold War now under threat of destruction.

 

By Lucy Hamilton

 

The scale of the survey and the complexity of the remains dictate how the teams approach their survey work. Trevor Pearson, Head of Technical Survey and Graphics based in York explains, “The surveys we carry out are generally at scales between 1:500 to 1:2500 to a level of detail that depends on the questions that need to be answered. Detailed mapping of a site can take several weeks to complete as we tease out the evidence of how the area has developed over time.  If parts of the site are extremely complex and the earthwork remains require close, painstaking analysis, it’s not unusual for us to fall back onto the simplest technology available – 30m tapes and a drawing board! However most of our work lends itself to the very latest in GPS technology.”

English Heritage has been using Trimble GPS for over 10 years and has a long-standing relationship with its UK distributor, KOREC. Conse-quently their GPS toolbox is well stocked with compatible systems enabling the team to select the right tool for the job.

Trevor continues, “If we need a rapid assessment of a site, a landscape survey at 1:2500 is more than adequate and the emphasis is on portability of equipment. Our solution is Trimble’s hand held GeoXT GPS with a belt mounted GeoBeacon to provide high quality real-time beacon corrections and sub-metre accuracy in the field. This lightweight system has proved invaluable, enabling the archaeologist to explore a site unencumbered by too much survey equipment whilst still having the capability to accurately locate any remains encountered and map the main elements. Using this system we can get a broad understanding of how an entire landscape has developed over time. However for more detailed work, survey grade DGPS is our first choice and we have several systems available to us from the older 4800 to the very latest in technology, the R8 GNSS - a future proof GLONASS enabled receiver allowing us to work near buildings and trees. If satellite reception is a problem, we also have a Trimble 5600 robotic total station available.”

English Heritage purchased the R8 equipment in February 2007 to update their 10 year old 4800 systems and also prepare for further technological developments with a system that would be capable of receiving the future L5 broadcast signal. The first real test of the GLONASS technology will come when the system is used on a current project to record the remains of lead mining in the steep-sided Scordale Valley, north of Appleby in Cumbria. The team is hoping that the R8 will allow them to work at the foot of the valley where a third or more of the sky can be obscured by hill slope.

 

Trimble’s hand-held GeoXT and GeoBeacon .

VRS Technology

The survey team has also been quick to reap the benefits of Trimble VRS Now, a service that provides instant access to RTK corrections across Great Britain. The team reports significant time savings on site and back at the office.  There is no longer any need to establish a base station each day or post-process data against the OS active station network to get the best fit to the National Grid. Although all the new equipment is VRS capable, a decision was taken to maintain the flexibility of having a base station as many of the sites the team works on are in areas where mobile phone reception is a problem and the VRS network consequently might not be available. Plans are currently being made to survey the earthworks of a Roman fort at Whitley Castle in the hills located above the market town of Alston and Trevor Pearson deemed this to be a perfect testing ground for VRS before embarking on the main survey. “Despite initial scepticism that VRS would work in this remote location, the equipment soon locked on to the network and received an uninterrupted flow of data for the whole day. This means that the Roman fort survey can be planned around using the VRS technology saving us both site and office time, freeing up an additional system and most importantly, dispensing with the need to guard a base station in a field full of inquisitive cows and sheep!”

 

Combining the Technologies

The compatibility of Trimble systems means that the new R8 equipment can be used alongside existing 5800 receivers and this has worked to great effect at the recent Scordale project in the North Pennines. This project was established in partnership with the Ministry of Defence and the North Pennines Area of Outstanding Natural Beauty to investigate the remains of a post-medieval lead mining landscape within the Scordale valley, which forms part of the Warcop military training area. The remains of mine shafts, processing areas, waste heaps, track ways, leats and the footprints of demolished buildings stretch for 2km along the valley bottom and for a considerable height up the steep valley sides. The vast majority of these remains date from the 19th and early part of the 20th century and have never been mapped before. A detailed survey at 1:1000 scale was required for those parts of the site where remains were best preserved and under most threat of erosion from the Scordale Beck. These areas were surveyed using a combination of the R8 and 5800 backed up with hand measurement and drawings where remains were very complex. The site also lent itself to the use of English Heritage’s hand-held mapping GPS - the GeoXT - which was used to survey the rest of the valley at 1:2500 scale. Data forms were created back at the York office in FastMap Office software and then uploaded onto the GeoXT to enable users to record basic attribute information on each feature mapped.

 

Future Plans

In the next few months English Heritage expects use of the R8 kit to spread to the offices beyond York and the team is confident that VRS will continue to bring noticeable time savings both on site and in the office. Trevor concludes, “KOREC’s sales and technical staff have played a key role in helping to develop our use of new equipment and services like VRS and a strong working relationship exists between us. Our approach is to use the most suitable method of survey for the demands of the job - tape, hand-held GPS, robotic total stations or survey grade GPS  - and our acquisition of VRS and GLONASS technology are important additions to our survey toolbox.”

 

Lucy Hamilton  Media Liaison at KOREC. All information kindly supplied by Trevor Pearson, Head of Technical Survey and Graphic’s based in York